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Sample records for ferroelectric single crystal

  1. Single crystal ternary oxide ferroelectric integration with Silicon

    NASA Astrophysics Data System (ADS)

    Bakaul, Saidur; Serrao, Claudy; Youun, Long; Khan, Asif; Salahuddin, Sayeef

    2015-03-01

    Integrating single crystal, ternary oxide ferroelectric thin film with Silicon or other arbitrary substrates has been a holy grail for the researchers since the inception of microelectronics industry. The key motivation is that adding ferroelectric materials to existing electronic devices could bring into new functionality, physics and performance improvement such as non-volatility of information, negative capacitance effect and lowering sub-threshold swing of field effect transistor (FET) below 60 mV/decade in FET [Salahuddin, S, Datta, S. Nano Lett. 8, 405(2008)]. However, fabrication of single crystal ferroelectric thin film demands stringent conditions such as lattice matched single crystal substrate and high processing temperature which are incompatible with Silicon. Here we report on successful integration of PbZr0.2Ti0.8O3 in single crystal form with by using a layer transfer method. The lattice structure, surface morphology, piezoelectric coefficient d33, dielectric constant, ferroelectric domain switching and spontaneous and remnant polarization of the transferred PZT are as good as these characteristics of the best PZT films grown by pulsed laser deposition on lattice matched oxide substrates. We also demonstrate Si based, FE gate controlled FET devices.

  2. Ferroelectric Single-Crystal Gated Graphene/Hexagonal-BN/Ferroelectric Field-Effect Transistor.

    PubMed

    Park, Nahee; Kang, Haeyong; Park, Jeongmin; Lee, Yourack; Yun, Yoojoo; Lee, Jeong-Ho; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok

    2015-11-24

    The effect of a ferroelectric polarization field on the charge transport in a two-dimensional (2D) material was examined using a graphene monolayer on a hexagonal boron nitride (hBN) field-effect transistor (FET) fabricated using a ferroelectric single-crystal substrate, (1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT). In this configuration, the intrinsic properties of graphene were preserved with the use of an hBN flake, and the influence of the polarization field from PMN-PT could be distinguished. During a wide-range gate-voltage (VG) sweep, a sharp inversion of the spontaneous polarization affected the graphene channel conductance asymmetrically as well as an antihysteretic behavior. Additionally, a transition from antihysteresis to normal ferroelectric hysteresis occurred, depending on the V(G) sweep range relative to the ferroelectric coercive field. We developed a model to interpret the complex coupling among antihysteresis, current saturation, and sudden conductance variation in relation with the ferroelectric switching and the polarization-assisted charge trapping, which can be generalized to explain the combination of 2D structured materials with ferroelectrics.

  3. Image plane digital holographic microscope for the inspection of ferroelectric single crystals

    NASA Astrophysics Data System (ADS)

    Psota, Pavel; Mokrý, Pavel; Lédl, Vít; Vojtíšek, Petr

    2016-12-01

    One of the most important characteristics in the research and application of ferroelectric materials is the appearance of the domain patterns, which take place in phenomena such as ferroelectric phase transitions or ferroelectric switching. The ability to visualize domains is the key factor that enables the progress in the research of these extremely interesting phenomena. However, the three-dimensional visualization of the ferroelectric domain patterns in the whole volume of the ferroelectric single crystal is not a straightforward task. We present the optical method, which allows the acquisition of quantitative and qualitative data substantial for the ferroelectric domain research. The principle of the method is based on image plane digital holographic microscopy (DHM). We used DHM setup outcomes from a Mach-Zehnder type of interferometer and phase-shifting digital holography. The studied specimen is a single crystal of barium titanate. It is demonstrated that the use of solid-state thin-film transparent electrodes of indium tin oxide greatly reduces the unwanted wavefront distortions, which are frequently produced in liquid electrodes. Using this approach, it is possible to greatly improve the DHM measurements in low applied electric fields. Thanks to the properties of the setup, real-time observation of domain walls growth or existing patterns of the ferroelectric crystal is possible.

  4. Digital holographic tomography method for 3D observation of domain patterns in ferroelectric single crystals

    NASA Astrophysics Data System (ADS)

    Mokrý, Pavel; Psota, Pavel; Steiger, Kateřina; Václavík, Jan; Vápenka, David; Doleček, Roman; Vojtíšek, Petr; Sládek, Juraj; Lédl, Vít.

    2016-11-01

    We report on the development and implementation of the digital holographic tomography for the three-dimensio- nal (3D) observations of the domain patterns in the ferroelectric single crystals. Ferroelectric materials represent a group of materials, whose macroscopic dielectric, electromechanical, and elastic properties are greatly in uenced by the presence of domain patterns. Understanding the role of domain patterns on the aforementioned properties require the experimental techniques, which allow the precise 3D measurements of the spatial distribution of ferroelectric domains in the single crystal. Unfortunately, such techniques are rather limited at this time. The most frequently used piezoelectric atomic force microscopy allows 2D observations on the ferroelectric sample surface. Optical methods based on the birefringence measurements provide parameters of the domain patterns averaged over the sample volume. In this paper, we analyze the possibility that the spatial distribution of the ferroelectric domains can be obtained by means of the measurement of the wavefront deformation of the transmitted optical wave. We demonstrate that the spatial distribution of the ferroelectric domains can be determined by means of the measurement of the spatial distribution of the refractive index. Finally, it is demonstrated that the measurements of wavefront deformations generated in ferroelectric polydomain systems with small variations of the refractive index provide data, which can be further processed by means of the conventional tomographic methods.

  5. Elastic Domain Wall Waves in Ferroelectric Ceramics and Single Crystals

    DTIC Science & Technology

    1988-07-01

    and identify by block number) " This report reviews research on acoustic guided waves along poling transitions in counter- poled ferroelectric ceramics...INTRODUCTION........................................ 1 II. GENERAL REVIEW . .. .......... ........... ... 2 (a) COUNTERPOLED CERAMICS...and better understanding of new ferroelectric materials. II. GENERAL REVIEW The initial phase of this project was an in-depth study of elastic wave

  6. Mechanical confinement for tuning ferroelectric response in PMN-PT single crystal

    NASA Astrophysics Data System (ADS)

    Patel, Satyanarayan; Chauhan, Aditya; Vaish, Rahul

    2015-02-01

    Ferroelectrics form an important class of materials and are employed for a variety of applications. However, specific applications dictate the need of tailored ferroelectric response. This creates a requirement to obtain ferroelectric materials with tunable properties. Generally, chemical modifications or domain engineering are employed to this effect. This study attempts to shed light on the use of compressive pre-stresses for tuning and enhancing the ferroelectric properties. For the purpose, polarization versus electric field hysteresis data for 68Pb(Mn1/3Nb2/3)O3-32PbTiO3 (PMN-PT) single crystals were obtained as a function of uniaxial compressive stresses and operating temperatures. These data were utilized to investigate the effects of mechanical confinement for four individual case studies of electrocaloric effect, electrical energy storage, pyroelectric, and piezoelectric effect. A significant improvement was obtained for all case studies. The adiabatic temperature change was improved by ≈80% (28 MPa, 353 K); energy storage density increased by a factor of five (28 MPa, 353 K); pyroelectric figure of merits improved by an order of magnitude (21 MPa) and the piezoelectric coefficient was tailored (variable stress). The results offer promising insight into the use of directional confinement for improving application specific ferroelectric properties in PMN-PT single crystal.

  7. Effect of amino acid doping on the growth and ferroelectric properties of triglycine sulphate single crystals

    SciTech Connect

    Raghavan, C.M.; Sankar, R.; Mohan Kumar, R.; Jayavel, R.

    2008-02-05

    Effect of amino acids (L-leucine and isoleucine) doping on the growth aspects and ferroelectric properties of triglycine sulphate crystals has been studied. Pure and doped crystals were grown from aqueous solution by low temperature solution growth technique. The cell parameter values were found to significantly vary for doped crystals. Fourier transform infrared analysis confirmed the presence of functional groups in the grown crystal. Morphology study reveals that amino acid doping induces faster growth rate along b-direction leading to a wide b-plane and hence suitable for pyroelectric detector applications. Ferroelectric domain structure has been studied by atomic force microscopy and hysteresis measurements reveal an increase of coercive field due to the formation of single domain pattern.

  8. Enhanced electrocaloric cooling in ferroelectric single crystals by electric field reversal

    NASA Astrophysics Data System (ADS)

    Ma, Yang-Bin; Novak, Nikola; Koruza, Jurij; Yang, Tongqing; Albe, Karsten; Xu, Bai-Xiang

    2016-09-01

    An improved thermodynamic cycle is validated in ferroelectric single crystals, where the cooling effect of an electrocaloric refrigerant is enhanced by applying a reversed electric field. In contrast to the conventional adiabatic heating or cooling by on-off cycles of the external electric field, applying a reversed field is significantly improving the cooling efficiency, since the variation in configurational entropy is increased. By comparing results from computer simulations using Monte Carlo algorithms and experiments using direct electrocaloric measurements, we show that the electrocaloric cooling efficiency can be enhanced by more than 20% in standard ferroelectrics and also relaxor ferroelectrics, like Pb (Mg1 /3 /Nb2 /3)0.71Ti0.29O3 .

  9. High performance relaxor-based ferroelectric single crystals for ultrasonic transducer applications.

    PubMed

    Chen, Yan; Lam, Kwok-Ho; Zhou, Dan; Yue, Qingwen; Yu, Yanxiong; Wu, Jinchuan; Qiu, Weibao; Sun, Lei; Zhang, Chao; Luo, Haosu; Chan, Helen L W; Dai, Jiyan

    2014-07-29

    Relaxor-based ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) have drawn much attention in the ferroelectric field because of their excellent piezoelectric properties and high electromechanical coupling coefficients (d33~2000 pC/N, kt~60%) near the morphotropic phase boundary (MPB). Ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals also possess outstanding performance comparable with PMN-PT single crystals, but have higher phase transition temperatures (rhombohedral to tetragonal Trt, and tetragonal to cubic Tc) and larger coercive field Ec. Therefore, these relaxor-based single crystals have been extensively employed for ultrasonic transducer applications. In this paper, an overview of our work and perspectives on using PMN-PT and PIN-PMN-PT single crystals for ultrasonic transducer applications is presented. Various types of single-element ultrasonic transducers, including endoscopic transducers, intravascular transducers, high-frequency and high-temperature transducers fabricated using the PMN-PT and PIN-PMN-PT crystals and their 2-2 and 1-3 composites are reported. Besides, the fabrication and characterization of the array transducers, such as phased array, cylindrical shaped linear array, high-temperature linear array, radial endoscopic array, and annular array, are also addressed.

  10. High Performance Relaxor-Based Ferroelectric Single Crystals for Ultrasonic Transducer Applications

    PubMed Central

    Chen, Yan; Lam, Kwok-Ho; Zhou, Dan; Yue, Qingwen; Yu, Yanxiong; Wu, Jinchuan; Qiu, Weibao; Sun, Lei; Zhang, Chao; Luo, Haosu; Chan, Helen L. W.; Dai, Jiyan

    2014-01-01

    Relaxor-based ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) have drawn much attention in the ferroelectric field because of their excellent piezoelectric properties and high electromechanical coupling coefficients (d33∼2000 pC/N, kt∼60%) near the morphotropic phase boundary (MPB). Ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals also possess outstanding performance comparable with PMN-PT single crystals, but have higher phase transition temperatures (rhombohedral to tetragonal Trt, and tetragonal to cubic Tc) and larger coercive field Ec. Therefore, these relaxor-based single crystals have been extensively employed for ultrasonic transducer applications. In this paper, an overview of our work and perspectives on using PMN-PT and PIN-PMN-PT single crystals for ultrasonic transducer applications is presented. Various types of single-element ultrasonic transducers, including endoscopic transducers, intravascular transducers, high-frequency and high-temperature transducers fabricated using the PMN-PT and PIN-PMN-PT crystals and their 2-2 and 1-3 composites are reported. Besides, the fabrication and characterization of the array transducers, such as phased array, cylindrical shaped linear array, high-temperature linear array, radial endoscopic array, and annular array, are also addressed. PMID:25076222

  11. Flexible ferroelectric organic crystals

    PubMed Central

    Owczarek, Magdalena; Hujsak, Karl A.; Ferris, Daniel P.; Prokofjevs, Aleksandrs; Majerz, Irena; Szklarz, Przemysław; Zhang, Huacheng; Sarjeant, Amy A.; Stern, Charlotte L.; Jakubas, Ryszard; Hong, Seungbum; Dravid, Vinayak P.; Stoddart, J. Fraser

    2016-01-01

    Flexible organic materials possessing useful electrical properties, such as ferroelectricity, are of crucial importance in the engineering of electronic devices. Up until now, however, only ferroelectric polymers have intrinsically met this flexibility requirement, leaving small-molecule organic ferroelectrics with room for improvement. Since both flexibility and ferroelectricity are rare properties on their own, combining them in one crystalline organic material is challenging. Herein, we report that trisubstituted haloimidazoles not only display ferroelectricity and piezoelectricity—the properties that originate from their non-centrosymmetric crystal lattice—but also lend their crystalline mechanical properties to fine-tuning in a controllable manner by disrupting the weak halogen bonds between the molecules. This element of control makes it possible to deliver another unique and highly desirable property, namely crystal flexibility. Moreover, the electrical properties are maintained in the flexible crystals. PMID:27734829

  12. Flexible ferroelectric organic crystals

    NASA Astrophysics Data System (ADS)

    Owczarek, Magdalena; Hujsak, Karl A.; Ferris, Daniel P.; Prokofjevs, Aleksandrs; Majerz, Irena; Szklarz, Przemysław; Zhang, Huacheng; Sarjeant, Amy A.; Stern, Charlotte L.; Jakubas, Ryszard; Hong, Seungbum; Dravid, Vinayak P.; Stoddart, J. Fraser

    2016-10-01

    Flexible organic materials possessing useful electrical properties, such as ferroelectricity, are of crucial importance in the engineering of electronic devices. Up until now, however, only ferroelectric polymers have intrinsically met this flexibility requirement, leaving small-molecule organic ferroelectrics with room for improvement. Since both flexibility and ferroelectricity are rare properties on their own, combining them in one crystalline organic material is challenging. Herein, we report that trisubstituted haloimidazoles not only display ferroelectricity and piezoelectricity--the properties that originate from their non-centrosymmetric crystal lattice--but also lend their crystalline mechanical properties to fine-tuning in a controllable manner by disrupting the weak halogen bonds between the molecules. This element of control makes it possible to deliver another unique and highly desirable property, namely crystal flexibility. Moreover, the electrical properties are maintained in the flexible crystals.

  13. Ferroelectric liquid crystal display

    NASA Technical Reports Server (NTRS)

    York, Paul K. (Inventor)

    1977-01-01

    A ferroelectric liquid crystal display device employs capacitance spoiling layers to minimize unneeded capacitances created by crossovers of X and Y address lines and to accurately define desired capacitances. The spoiler layers comprise low dielectric constant layers which space electrodes from the ferroelectric at crossover points where capacitance is not needed for device operation.

  14. Characterizing new compositions of [001]C relaxor ferroelectric single crystals using a work-energy model

    NASA Astrophysics Data System (ADS)

    Gallagher, John A.

    2016-04-01

    The desired operating range of ferroelectric materials with compositions near the morphotropic phase boundary is limited by field induced phase transformations. In [001]C cut and poled relaxor ferroelectric single crystals the mechanically driven ferroelectric rhombohedral to ferroelectric orthorhombic phase transformation is hindered by antagonistic electrical loading. Instability around the phase transformation makes the current experimental technique for characterization of the large field behavior very time consuming. Characterization requires specialized equipment and involves an extensive set of measurements under combined electrical, mechanical, and thermal loads. In this work a mechanism-based model is combined with a more limited set of experiments to obtain the same results. The model utilizes a work-energy criterion that calculates the mechanical work required to induce the transformation and the required electrical work that is removed to reverse the transformation. This is done by defining energy barriers to the transformation. The results of the combined experiment and modeling approach are compared to the fully experimental approach and error is discussed. The model shows excellent predictive capability and is used to substantially reduce the total number of experiments required for characterization. This decreases the time and resources required for characterization of new compositions.

  15. Optimization of electrooptic and pieozoelectric coupling effects in tetragonal relaxor-PT ferroelectric single crystals.

    PubMed

    Sun, Enwei; Sang, Shijing; Yuan, Zhongyuan; Qi, Xudong; Zhang, Rui; Cao, Wenwu

    2015-08-15

    The electrooptic and piezoelectric coupling effects in tetragonal relaxor-based ferroelectric 0.62Pb(Mg1/3Nb2/3)O3-0.38PbTiO3 (PMN-0.38PT) and 0.88Pb(Zn1/3Nb2/3)O3-0.12PbTiO3 (PZN-0.12PT) single-domain crystals have been analyzed by the coordinate transformation. The orientation dependence of the electrooptic and half-wave voltage was calculated based on the full sets of refractive indices, electrooptic and piezoelectric coefficients. The optimum orientation cuts for achieving the best electrooptic coefficient and half-wave voltage were found. The lowset half-wave voltage is only 76 V for the PMN-0.38PT single-domain crystal. Compared to commonly used electrooptic crystal LiNbO3, tetragonal relaxor-PT ferroelectric single-domain crystals are much superior for optical modulation applications because of their much higher linear electrooptic coefficients and substantially lower half-wave voltages when the piezoelectric strain influence is considered.

  16. Optimization of electrooptic and pieozoelectric coupling effects in tetragonal relaxor-PT ferroelectric single crystals

    PubMed Central

    Sun, Enwei; Sang, Shijing; Yuan, Zhongyuan; Qi, Xudong; Zhang, Rui; Cao, Wenwu

    2015-01-01

    The electrooptic and piezoelectric coupling effects in tetragonal relaxor-based ferroelectric 0.62Pb(Mg1/3Nb2/3)O3-0.38PbTiO3 (PMN-0.38PT) and 0.88Pb(Zn1/3Nb2/3)O3-0.12PbTiO3 (PZN-0.12PT) single-domain crystals have been analyzed by the coordinate transformation. The orientation dependence of the electrooptic and half-wave voltage was calculated based on the full sets of refractive indices, electrooptic and piezoelectric coefficients. The optimum orientation cuts for achieving the best electrooptic coefficient and half-wave voltage were found. The lowset half-wave voltage is only 76 V for the PMN-0.38PT single-domain crystal. Compared to commonly used electrooptic crystal LiNbO3, tetragonal relaxor-PT ferroelectric single-domain crystals are much superior for optical modulation applications because of their much higher linear electrooptic coefficients and substantially lower half-wave voltages when the piezoelectric strain influence is considered. PMID:25954059

  17. Directionally controlled 3D ferroelectric single crystal growth in LaBGeO5 glass by femtosecond laser irradiation.

    PubMed

    Stone, Adam; Sakakura, Masaaki; Shimotsuma, Yasuhiko; Stone, Greg; Gupta, Pradyumna; Miura, Kiyotaka; Hirao, Kazuyuki; Dierolf, Volkmar; Jain, Himanshu

    2009-12-07

    Laser-fabrication of complex, highly oriented three-dimensional ferroelectric single crystal architecture with straight lines and bends is demonstrated in lanthanum borogermanate model glass using a high repetition rate femtosecond laser. Scanning micro-Raman microscopy shows that the c-axis of the ferroelectric crystal is aligned with the writing direction even after bending. A gradual rather than an abrupt transition is observed for the changing lattice orientation through bends up to approximately 14 degrees. Thus the single crystal character of the line is preserved along the bend through lattice straining rather than formation of a grain boundary.

  18. Enhanced ferroelectric polarization in tetragonally strained NaNbO3 thin film on single crystal Rh substrate

    NASA Astrophysics Data System (ADS)

    Maeng, W. J.; Jung, I.; Son, J. Y.

    2012-06-01

    Epitaxial NaNbO3 thin films were deposited on single crystal Rh substrates by pulsed laser deposition. The epitaxial NaNbO3 thin film exhibited the tetragonally stained structure with a c/a ratio of about 1.04 and a good ferroelectric property with the high remanent polarization (Pr) of about 40 μC/cm2. The piezoresponse force microscope study revealed that the epitaxial NaNbO3 thin film has a mosaic ferroelectric domain structure. A Pt/NaNbO3/Rh capacitor showed rapid ferroelectric switching behavior, which gives opportunity for a non-volatile memory application.

  19. Giant photovoltaic effect of ferroelectric domain walls in perovskite single crystals

    PubMed Central

    Inoue, Ryotaro; Ishikawa, Shotaro; Imura, Ryota; Kitanaka, Yuuki; Oguchi, Takeshi; Noguchi, Yuji; Miyayama, Masaru

    2015-01-01

    The photovoltaic (PV) effect in polar materials offers great potential for light-energy conversion that generates a voltage beyond the bandgap limit of present semiconductor-based solar cells. Ferroelectrics have received renewed attention because of the ability to deliver a high voltage in the presence of ferroelastic domain walls (DWs). In recent years, there has been considerable debate over the impact of the DWs on the PV effects, owing to lack of information on the bulk PV tensor of host ferroelectrics. In this article, we provide the first direct evidence of an unusually large PV response induced by ferroelastic DWs—termed ‘DW’-PV effect. The precise estimation of the bulk PV tensor in single crystals of barium titanate enables us to quantify the giant PV effect driven by 90° DWs. We show that the DW-PV effect arises from an effective electric field consisting of a potential step and a local PV component in the 90° DW region. This work offers a starting point for further investigation into the DW-PV effect of alternative systems and opens a reliable route for enhancing the PV properties in ferroelectrics based on the engineering of domain structures in either bulk or thin-film form. PMID:26443381

  20. Direct imaging of both ferroelectric and antiferromagnetic domains in multiferroic BiFeO3 single crystal using x-ray photoemission electron microscopy

    NASA Astrophysics Data System (ADS)

    Moubah, R.; Elzo, M.; El Moussaoui, S.; Colson, D.; Jaouen, N.; Belkhou, R.; Viret, M.

    2012-01-01

    In this work, we propose to study the magnetic and ferroelectric configurations in ferroelectric multidomain BiFeO3 single crystals. Using x-ray (magnetic) linear dichroism in a photoemission electron microscope (X-PEEM), we are able to directly image both the antiferromagnetic and ferroelectric domains. We find that inside one single ferroelectric domain several antiferromagnetic domains coexist. This is different from what was observed on epitaxial thin films, where the ferroelectric domains perfectly match the antiferromagnetic ones, but also from previous neutron measurements on ferroelectric monodomain single-crystals for which one single antiferromagnetic domain was identified. This underlines the fundamental differences between thin films, bulk samples, and single versus ferroelectric multidomain samples.

  1. Direct imaging of both ferroelectric and antiferromagnetic domains in multiferroic BiFeO{sub 3} single crystal using x-ray photoemission electron microscopy

    SciTech Connect

    Moubah, R.; Colson, D.; Viret, M.; Elzo, M.; Jaouen, N.; Belkhou, R.

    2012-01-23

    In this work, we propose to study the magnetic and ferroelectric configurations in ferroelectric multidomain BiFeO{sub 3} single crystals. Using x-ray (magnetic) linear dichroism in a photoemission electron microscope (X-PEEM), we are able to directly image both the antiferromagnetic and ferroelectric domains. We find that inside one single ferroelectric domain several antiferromagnetic domains coexist. This is different from what was observed on epitaxial thin films, where the ferroelectric domains perfectly match the antiferromagnetic ones, but also from previous neutron measurements on ferroelectric monodomain single-crystals for which one single antiferromagnetic domain was identified. This underlines the fundamental differences between thin films, bulk samples, and single versus ferroelectric multidomain samples.

  2. Millimeter-Wave Dielectric Properties of Single Crystal Ferroelectric and Dielectric Materials

    SciTech Connect

    McCloy, John S.; Korolev, Konstantin A.; Li, Zijing; Afsar, Mohammed N.; Sundaram, S. K.

    2011-01-03

    Transmittance measurements on various single crystal ferroelectric materials over a broad millimeter-wave frequency range have been performed. Frequency dependence of the complex dielectric permittivity has been determined in the millimeter wave region for the first time. The measurements have been employed using a free-space quasi-optical millimeter-wave spectrometer equipped with a set of high power backward wave oscillators (BWOs) as sources of coherent radiation, tunable in the range from 30 - 120 GHz. The uncertainties and possible sources of instrumentation and measurement errors related to the free-space millimeter-wave technique are discussed. This work has demonstrated that precise MMW permittivities can be obtained even on small thin crystals using the BWO quasi-optical approach.

  3. Self-Powered Ultrabroadband Photodetector Monolithically Integrated on a PMN-PT Ferroelectric Single Crystal.

    PubMed

    Fang, Huajing; Xu, Chao; Ding, Jie; Li, Qiang; Sun, Jia-Lin; Dai, Ji-Yan; Ren, Tian-Ling; Yan, Qingfeng

    2016-12-07

    Photodetectors capable of detecting two or more bands simultaneously with a single system have attracted extensive attentions because of their critical applications in image sensing, communication, and so on. Here, we demonstrate a self-powered ultrabroadband photodetector monolithically integrated on a 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PMN-28PT) single crystal. By combining the optothermal and pyroelectric effect, the multifunctional PMN-28PT single crystal can response to a wide wavelength range from UV to terahertz (THz). At room temperature, the photodetector could generate a pyroelectric current under the intermittent illumination of incident light in absence of external bias. A systematic study of the photoresponse was investigated. The pyroelectric current shows an almost linear relationship to illumination intensity. Benefiting from the excellent pyroelectric property of PMN-28PT single crystal and the optimized device architecture, the device exhibited a dramatic improvement in operation frequency up to 3 kHz without any obvious degradation in sensitivity. Such a self-powered photodetector with ultrabroadband response may open a window for the novel application of ferroelectric materials in optoelectronics.

  4. Measuring and Altering Ferroelectric Domain Structures in Lead Perovskite Single-Crystals

    NASA Astrophysics Data System (ADS)

    Harker, John Chamberlain

    Relaxor ferroelectric single-crystal materials PMN-PT and PZN-PT are currently of interest to the scientific community due to their enhanced properties and possible role as next-generation piezoelectric transducers in applications such as sonar and medical ultrasound. One key phenomenon affecting both the properties and the mechanical integrity of these materials is the ferroelectric domain structure within the material. In this work we examine the morphology and behavior of domain structures in PMN-29%PT. In order to do this we first present details of the construction and testing of a working piezo-response force microscope (PFM), and then use the PFM to verify a new domain observation technique called "relief polishing". Relief polishing is shown to reveal surface domains in the same manner as acid etching, preserving domain details as small as 0.5mum. Using these two techniques, we then determine that cutting and polishing strongly affect the surface and subsurface ferroelectric domain structures in PMN-29%PT. Specifically, we show that saw cutting can create characteristic striated domain structures as deep as 130mum within a sample, while straight polishing creates a characteristic domain structure known as the "fingerprint" pattern to a depth proportional to the size of the polishing grit, on the order of 0--12mum for grits as large as 15mum. We hypothesize that most samples contain these "skin effect" domain structures. In consequence, it is suggested that researchers presenting experimental results on domain structures should report the physical treatment history of the samples along with the experimental data.

  5. Anomalous phase diagram of ferroelectric (Ba,Ca)TiO3 single crystals with giant electromechanical response.

    PubMed

    Fu, Desheng; Itoh, Mitsuru; Koshihara, Shin-ya; Kosugi, Taichi; Tsuneyuki, Shinji

    2008-06-06

    We report the anomalous phase evolution in ferroelectric single crystals Ba1-xCaxTiO3 (0.02ferroelectric phase transition. In addition, large electromechanical responses in this class of crystals are also demonstrated. Our results indicate that an effective approach to control the ferroelectricity of perovskite oxide can be realized not only by the covalency between A site atom and oxygen but also by the substitution of A site with small ions with off-centering nature. Theoretical calculations support the idea that the off-center displacements of the smaller Ca ions in the Ba-site play an important role in the exotic natures of Ba1-xCaxTiO3.

  6. Millimeter-wave dielectric properties of single-crystal ferroelectric and dielectric materials.

    PubMed

    McCloy, John S; Korolev, Konstantin A; Li, Zijing; Afsar, Mohammed N; Sundaram, Shanmugavelayutham K

    2011-01-01

    Transmittance measurements on various single crystal ferroelectric and dielectric materials, BaTiO(3), SrTiO(3), LiNbO(3), LiTaO(3), (PbMg(1/3)Nb(2/3)O(3))0.73-(PbTiO(3))0.27, LaAlO(3), and Bi(4)Ge(3)O(12), over a broad millimeter-wave (MMW) frequency range have been performed. Frequency dependence of the complex dielectric permittivity has been measured in the MMW region using high-power sources for the first time, using a free-space, quasi-optical MMW spectrometer equipped with high-power backward wave oscillators (BWOs) as sources of coherent radiation, tunable in the range from 30 to 120 and 180 to 260 GHz. These results are compared with MMW permittivity of these materials obtained by other methods as well as to RF, microwave, and optical frequency permittivities for all the materials tested. The effects of both crystallographic orientation and quality of the surface polishing of the crystals have been examined. Uncertainties and possible sources of instrumentation and measurement errors related to the freespace MMW technique are discussed. This work demonstrates that precise MMW permittivity data can be obtained even on relatively small and thin crystals of different surface conditions and orientations using the high-power BWO-based quasioptical approach.

  7. Partially transformed relaxor ferroelectric single crystals with distributed phase transformation behavior

    NASA Astrophysics Data System (ADS)

    Gallagher, John A.

    2015-11-01

    Relaxor ferroelectric single crystals such as PMN-PT and PIN-PMN-PT undergo field driven phase transformations when electrically or mechanically loaded in crystallographic directions that provide a positive driving force for the transformation. The observed behavior in certain compositions is a phase transformation distributed over a range of fields without a distinct forward or reverse coercive field. This work focuses on the material behavior that is observed when the crystals are loaded sufficiently to drive a partial transformation and then unloaded, as might occur when driving a transducer to achieve high power levels. Distributed transformations have been modeled using a normal distribution of transformation thresholds. A set of experiments was conducted to characterize the hysteresis loops that occur with the partial transformations. In this work the normal distribution model is extended to include the partial transformations that occur when the field is reversed before the transformation is complete. The resulting hysteresis loops produced by the model are in good agreement with the experimental results.

  8. Relaxor-based ferroelectric single crystals: growth, domain engineering, characterization and applications.

    PubMed

    Sun, Enwei; Cao, Wenwu

    2014-08-01

    In the past decade, domain engineered relaxor-PT ferroelectric single crystals, including (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT), (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) and (1-x-y)Pb(In1/2Nb1/2)O3-yPb(Mg1/3Nb2/3)O3-xPbTiO3 (PIN-PMN-PT), with compositions near the morphotropic phase boundary (MPB) have triggered a revolution in electromechanical devices owing to their giant piezoelectric properties and ultra-high electromechanical coupling factors. Compared to traditional PbZr1-x Ti x O3 (PZT) ceramics, the piezoelectric coefficient d33 is increased by a factor of 5 and the electromechanical coupling factor k33 is increased from < 70% to > 90%. Many emerging rich physical phenomena, such as charged domain walls, multi-phase coexistence, domain pattern symmetries, etc., have posed challenging fundamental questions for scientists. The superior electromechanical properties of these domain engineered single crystals have prompted the design of a new generation electromechanical devices, including sensors, transducers, actuators and other electromechanical devices, with greatly improved performance. It took less than 7 years from the discovery of larger size PMN-PT single crystals to the commercial production of the high-end ultrasonic imaging probe "PureWave". The speed of development is unprecedented, and the research collaboration between academia and industrial engineers on this topic is truly intriguing. It is also exciting to see that these relaxor-PT single crystals are being used to replace traditional PZT piezoceramics in many new fields outside of medical imaging. The new ternary PIN-PMN-PT single crystals, particularly the ones with Mn-doping, have laid a solid foundation for innovations in high power acoustic projectors and ultrasonic motors, hinting another revolution in underwater SONARs and miniature actuation devices. This article intends to provide a comprehensive review on the development of relaxor-PT single crystals, spanning material discovery

  9. Relaxor-based ferroelectric single crystals: growth, domain engineering, characterization and applications

    PubMed Central

    Sun, Enwei; Cao, Wenwu

    2014-01-01

    In the past decade, domain engineered relaxor-PT ferroelectric single crystals, including (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT), (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) and (1-x-y)Pb(In1/2Nb1/2)O3-yPb(Mg1/3Nb2/3)O3-xPbTiO3 (PIN-PMN-PT), with compositions near the morphotropic phase boundary (MPB) have triggered a revolution in electromechanical devices owing to their giant piezoelectric properties and ultra-high electromechanical coupling factors. Compared to traditional PbZr1-xTixO3 (PZT) ceramics, the piezoelectric coefficient d33 is increased by a factor of 5 and the electromechanical coupling factor k33 is increased from < 70% to > 90%. Many emerging rich physical phenomena, such as charged domain walls, multi-phase coexistence, domain pattern symmetries, etc., have posed challenging fundamental questions for scientists. The superior electromechanical properties of these domain engineered single crystals have prompted the design of a new generation electromechanical devices, including sensors, transducers, actuators and other electromechanical devices, with greatly improved performance. It took less than 7 years from the discovery of larger size PMN-PT single crystals to the commercial production of the high-end ultrasonic imaging probe “PureWave”. The speed of development is unprecedented, and the research collaboration between academia and industrial engineers on this topic is truly intriguing. It is also exciting to see that these relaxor-PT single crystals are being used to replace traditional PZT piezoceramics in many new fields outside of medical imaging. The new ternary PIN-PMN-PT single crystals, particularly the ones with Mn-doping, have laid a solid foundation for innovations in high power acoustic projectors and ultrasonic motors, hinting another revolution in underwater SONARs and miniature actuation devices. This article intends to provide a comprehensive review on the development of relaxor-PT single crystals, spanning material discovery

  10. Néel-like domain walls in ferroelectric Pb(Zr,Ti)O3 single crystals

    PubMed Central

    Wei, Xian-Kui; Jia, Chun-Lin; Sluka, Tomas; Wang, Bi-Xia; Ye, Zuo-Guang; Setter, Nava

    2016-01-01

    In contrast to the flexible rotation of magnetization direction in ferromagnets, the spontaneous polarization in ferroelectric materials is highly confined along the symmetry-allowed directions. Accordingly, chirality at ferroelectric domain walls was treated only at the theoretical level and its real appearance is still a mystery. Here we report a Néel-like domain wall imaged by atom-resolved transmission electron microscopy in Ti-rich ferroelectric Pb(Zr1−xTix)O3 crystals, where nanometre-scale monoclinic order coexists with the tetragonal order. The formation of such domain walls is interpreted in the light of polarization discontinuity and clamping effects at phase boundaries between the nesting domains. Phase-field simulation confirms that the coexistence of both phases as encountered near the morphotropic phase boundary promotes the polarization to rotate in a continuous manner. Our results provide a further insight into the complex domain configuration in ferroelectrics, and establish a foundation towards exploring chiral domain walls in ferroelectrics. PMID:27539075

  11. Growth, Optical, Dielectric and Ferroelectric Properties of Non-Linear Optical Single Crystal: Glycine-Phthalic Acid

    NASA Astrophysics Data System (ADS)

    Suresh, Sagadevan

    2016-11-01

    Single crystals of glycine-phthalic acid (GPA) were grown by slow evaporation process using aqueous solution. X-ray diffraction analysis was used to examine its cell structure and it was found that the GPA crystal corresponded to the orthorhombic system. To identify absorption range and cut-off wavelength for the GPA crystal, UV-visible spectrum was recorded. UV-visible spectroscopy was used to study the optical constants such as the refractive index, the extinction coefficient, electrical susceptibility, and optical conductivity. As a function of different frequencies and temperatures, the dielectric constant and the dielectric loss were examined. The electrical properties like plasma energy, Penn gap, Fermi energy, and polarizability were determined for the analysis of the second harmonic generation (SHG). Using the Kurtz powder technique, the SHG of the GPA crystal was studied. Investigations relating to hysteresis were carried out to ascertain the ferroelectric nature of the material.

  12. Growth and piezo-/ferroelectric properties of PIN-PMN-PT single crystals

    NASA Astrophysics Data System (ADS)

    Li, Xiuzhi; Wang, Zujian; He, Chao; Long, Xifa; Ye, Zuo-Guang

    2012-02-01

    Ternary solid solution crystals of 0.19Pb(In1/2Nb1/2)O3- 0.46Pb(Mg1/3Nb2/3)O3- 0.35PbTiO3 [PIMNT(19/46/35)] with dimensions of 35 × 38 × 15 mm3 were grown by the top-seeded solution growth (TSSG) method. The dielectric, piezo- and ferroelectric properties of the grown crystals were characterized. The ternary piezocrystals exhibit a Curie temperature TC = 190 °C and a tetragonal-rhombohedral phase transition temperature TR-T = 130 °C, which are increased significantly compared with TC ≈ 155 °C and TR-T ≈ 80 °C of PMN-PT crystals. The dielectric constant (ɛ') and dielectric loss tangent (tan δ) are 4300 and 0.40 at room temperature. The piezoelectric coefficient d33 is found to be 2380 pC/N. The longitudinal electromechanical coupling factor k33 reaches 90% at room temperature. A peak-to-peak bipolar strain value of 0.13% is obtained at E ≈ ± 14 kV/cm. The coercive field Ec and remanent polarization Pr are 5.50 kV/cm and 27.10 μC/cm2, respectively, which are also improved from the vales of PMN-PT crystals.

  13. Studies on conventional and Sankaranarayanan-Ramasamy (SR) method grown ferroelectric glycine phosphite (GPI) single crystals

    NASA Astrophysics Data System (ADS)

    Senthil Pandian, M.; Pattanaboonmee, N.; Ramasamy, P.; Manyum, P.

    2011-01-01

    Transparent single crystals of glycine phosphite were grown by Sankaranarayanan-Ramasamy (SR) method and conventional slow evaporation solution technique (SEST) which had the sizes of 100 mm in length, 30 mm diameter and 10×11×8 mm 3. The conventional slow evaporation and Sankaranarayanan-Ramasamy method grown glycine phosphite single crystals were characterized using laser damage threshold, chemical etching, Vickers microhardness, UV-vis-NIR and dielectric analysis. The laser damage threshold value was higher in SR method grown GPI crystal as against conventional method grown crystal. The SR method grown GPI has higher hardness and also higher transmittance compared to conventional method grown crystal. The chemical etching and dielectric loss measurements indicate that the crystal grown by SR method has low density of defects and low value of dielectric loss compared to conventional method grown GPI crystal.

  14. Bulk crystal growth, optical, mechanical and ferroelectric properties of new semiorganic nonlinear optical and piezoelectric Lithium nitrate monohydrate oxalate single crystal

    NASA Astrophysics Data System (ADS)

    Dalal, Jyoti; Kumar, Binay

    2016-01-01

    New semiorganic nonlinear optical single crystals of Lithium nitrate oxalate monohydrate (LNO) were grown by slow evaporation solution technique. Single crystal X-ray diffraction study indicated that LNO crystal belongs to the triclinic system with space group P1. Various functional groups present in the material were identified by FTIR and Raman analysis. UV-vis study showed the high transparency of crystals with a wide band gap 5.01 eV. Various Optical constants i.e. Urbach energy (Eu), extinction coefficient (K), refractive index, optical conductivity, electric susceptibility with real and imaginary parts of dielectric constant were calculated using the transmittance data which have applications in optoelectronic devices. A sharp emission peak was found at 438 nm in photoluminescence measurement, which revealed suitability of crystal for fabricating violet lasers. In dielectric studies, a peak has been observed at 33 °C which is due to ferroelectric to paraelectric phase transition. Piezoelectric charge coefficients (d33 = 9.2 pC/N and g33) have been calculated, which make it a suitable for piezoelectric devices applications. In ferroelectric studies, a saturated loop was found in which the values of coercive field and remnant polarization were found to be 2.18 kV/cm and 0.39 μC/cm2, respectively. Thermal behavior was studied by TGA and DSC studies. The relative SHG efficiency of LNO was found to be 1.2 times that of KDP crystal. In microhardness study, Meyer's index value was found to be 1.78 which revealed its soft nature. These optical, dielectric, piezoelectric, ferroelectric, mechanical and non-linear optical properties of grown crystal establish the usefulness of this material for optoelectronics, non-volatile memory and piezoelectric devices applications.

  15. Investigations on ferroelectric PMN-PT and PZN-PT single crystals ability for power or resonant actuators.

    PubMed

    Lebrun, L; Sebald, G; Guiffard, B; Richard, C; Guyomar, D; Pleska, E

    2004-04-01

    Ferroelectric single crystals of PZN-PT and PMN-PT exhibit outstanding properties: high charge coefficient (dij), high coupling factor (kij) and high strain levels under DC fields. Besides, their mechanical quality factor is believed to be low. Their usefulness for non-resonant or large bandwidth transducers has therefore been previously investigated. However, few studies have been devoted to the dielectric and mechanical losses of single crystals and to their stability under high levels of excitations (electric fields, temperature and mechanical stress). A knowledge and understanding of such performances is needed to determine whether single crystals are suitable materials for power or resonant transducers. In this work, losses and non-linearity versus external excitations are investigated. Dielectric losses and mechanical losses are measured versus electric field for different compositions, orientations. The evolution of d33 and epsilonT33 are obtained versus electric field and temperature for the longitudinal mode. Strain and hysteresis versus sweep mode (up and down) are measured near the resonance frequency using a laser Doppler vibrometer.

  16. Effects of composition and temperature on the large field behavior of [011]{sub C} relaxor ferroelectric single crystals

    SciTech Connect

    Gallagher, John A.; Lynch, Christopher S.; Tian, Jian

    2014-08-04

    The large field behavior of [011]{sub C} cut relaxor ferroelectric lead indium niobate–lead magnesium niobate–lead titanate, xPb(In{sub 1/2}Nb{sub 1/2})O{sub 3}-(1-x-y)Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-yPbTiO{sub 3}, single crystals was experimentally characterized in the piezoelectric d{sub 322}-mode configuration under combined mechanical, electrical, and thermal loading. Increasing the concentration of lead indium niobate and decreasing the concentration of lead titanate in compositions near the morphotropic phase boundary resulted in a decrease of mechanical compliance, dielectric permittivity, and piezoelectric coefficients as well as a shift from a continuous to a discontinuous transformation.

  17. Synthesis, growth, optical and mechanical studies of ferroelectric urea-oxalic acid single crystals

    NASA Astrophysics Data System (ADS)

    Vizhi, R. Ezhil; Dhivya, R.; Babu, D. Rajan

    2016-10-01

    A single crystal of urea oxalic acid was grown by slow evaporation method. The lattice parameters are a=5.13 Å, b=12.48 Å, c=7.07 Å, β=98.13° with V=448.5 Å3 which belongs to monoclinic system with space group P21/c obtained from single crystal X-ray diffraction analysis. UV-visible spectrum was recorded from the wavelength region of 200-800 nm and its cutoff wavelength was found to be 270 nm. Optical energy band gap of 4.57 eV was determined using Tau's plot relation. Fourier transform infrared vibrational spectrum confirmed the presence of N-H asymmetric stretching which occurs at 3444 cm-1 and 1853 cm-1 arising due to the amide C=O symmetric stretching. The emission was observed at 364 nm from the photoluminescence spectrum. The mechanical stability of the grown crystal was estimated by Vickers microhardness studies and it is evident that the grown crystal belongs to soft material category. Hardness related parameters such as elastic stiffness constant, fracture mechanics, brittleness index and yield strength were also evaluated. The dielectric constant and dielectric loss of the grown crystal were carried out as a function of frequency for different temperatures.

  18. Piezoelectric and ferroelectric properties of lead-free niobium-rich potassium lithium tantalate niobate single crystals

    SciTech Connect

    Li, Jun; Li, Yang; Zhou, Zhongxiang; Guo, Ruyan; Bhalla, Amar S.

    2014-01-01

    Graphical abstract: - Highlights: • Lead-free K{sub 0.95}Li{sub 0.05}Ta{sub 1−x}Nb{sub x}O{sub 3} single crystals were grown using the top-seeded melt growth method. • The piezoelectric and ferroelectric properties of as-grown crystals were systematically investigated. • The piezoelectric properties are very attractive, e.g. for x = 0.60 composition, k{sub t} ≈ 70%, k{sub 31} ≈ 70%, k{sub 33} ≈ 77%, d{sub 31} ≈ 230 pC/N, d{sub 33} ≈ 600 pC/N. • The coercive fields of P–E hysteresis loops are quite small, about or less than 1 kV/mm. - Abstract: Lead-free potassium lithium tantalate niobate single crystals with the composition of K{sub 0.95}Li{sub 0.05}Ta{sub 1−x}Nb{sub x}O{sub 3} (abbreviated as KLTN, x = 0.51, 0.60, 0.69, 0.78) were grown using the top-seeded melt growth method. Their piezoelectric and ferroelectric properties in as-grown crystals have been systematically investigated. The phase transitions and Curie temperatures were determined from dielectric and pyroelectric measurements. Piezoelectric coefficients and electromechanical coupling factors in thickness mode, length-extensional mode and longitudinal mode were obtained. The piezoelectric properties are very attractive, e.g. for x = 0.60 composition, k{sub t} ≈ 70%, k{sub 31} ≈ 70%, k{sub 33} ≈ 77%, d{sub 31} ≈ 230 pC/N, d{sub 33} ≈ 600 pC/N are comparable to the lead-based PZT composition. The polarization versus electric field hysteresis loops show saturated shapes. In short, lead-free niobium-rich KLTN system possesses comparable properties to those in important lead-based piezoelectric material nowadays.

  19. Relaxor Ferroelectric Single Crystal Based Hybrid Actuator for Underwater Acoustic Noise Generation

    DTIC Science & Technology

    2002-05-01

    Undergraduate Students . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 11 Patents 131 7 List of Figures 1 Upper bound on specific...lectrostrictor Figure 1: Upper bound on specific work vs. frequency for various actuation media. SMA is shape- memory alloy; PZN-PT is single-crystal...chambers to be filled. Both chips were filled successfully on the first attempts to fill them. These results provided the needed confidence to fill and

  20. Ferroelectric domain structures in <001>-oriented K{sub 0.15}Na{sub 0.85}NbO{sub 3} lead-free single crystal

    SciTech Connect

    Chen, Yan; Wong, Chi-Man; Yau, Hei-Man; Dai, Jiyan; Deng, Hao; Luo, Haosu; Wang, Danyang; Yan, Zhibo; Chan, Helen L. W.

    2015-03-15

    In this work, ferroelectric domain structures of <001 >-oriented K{sub 0.15}Na{sub 0.85}NbO{sub 3} single crystal are characterized. Transmission electron microscopy (TEM) observation revealed high-density of laminate domain structures in the crystal and the lattices of the neighboring domains are found to be twisted in a small angle. Superlattice diffraction spots of 1/2 (eeo) and 1/2 (ooe) in electron diffraction patterns are observed in the crystal, revealing the a{sup +}a{sup +}c{sup −} tilting of oxygen octahedral in the perovskite structure. The piezoresponse of domains and in-situ poling responses of K{sub 0.15}Na{sub 0.85}NbO{sub 3} crystal are observed by piezoresponse force microscopy (PFM), and the results assure its good ferroelectric properties.

  1. Phase transition sequence in ferroelectric Aurivillius compounds investigated by single crystal X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Boullay, P.; Tellier, J.; Mercurio, D.; Manier, M.; Zuñiga, F. J.; Perez-Mato, J. M.

    2012-09-01

    The investigation of the phase transition sequence in SrBi2Ta2O9 (SBT) and SrBi2Nb2O9 (SBN) is reported using single-crystal X-ray diffraction. By monitoring specific reflections as a function of temperature, sensitive either to the superstructure formation or to polar displacements, it was possible to check the existence or not of an intermediate phase. This latter was confirmed in SBT, but within experimental accuracy could not be detected in SBN.

  2. Switching ferroelectric domain configurations using both electric and magnetic fields in Pb(Zr,Ti)O3–Pb(Fe,Ta)O3 single-crystal lamellae

    PubMed Central

    Evans, D. M.; Schilling, A.; Kumar, Ashok; Sanchez, D.; Ortega, N.; Katiyar, R. S.; Scott, J. F.; Gregg, J. M.

    2014-01-01

    Thin single-crystal lamellae cut from Pb(Zr,Ti)O3–Pb(Fe,Ta)O3 ceramic samples have been integrated into simple coplanar capacitor devices. The influence of applied electric and magnetic fields on ferroelectric domain configurations has been mapped, using piezoresponse force microscopy. The extent to which magnetic fields alter the ferroelectric domains was found to be strongly history dependent: after switching had been induced by applying electric fields, the susceptibility of the domains to change under a magnetic field (the effective magnetoelectric coupling parameter) was large. Such large, magnetic field-induced changes resulted in a remanent domain state very similar to the remanent state induced by an electric field. Subsequent magnetic field reversal induced more modest ferroelectric switching. PMID:24421376

  3. Effect of field driven phase transformations on the loss tangent of relaxor ferroelectric single crystals

    NASA Astrophysics Data System (ADS)

    Gallagher, John A.; Liu, Tieqi; Lynch, Christopher S.

    2013-02-01

    The effect of a bias stress induced phase transformation on the large field dielectric loss in [001] cut and poled single crystal stack actuators of (1 - x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT, x = 32) was experimentally characterized. Dielectric loss was observed to increase with compressive preload and electric field amplitude. The dielectric loss was determined by measuring the area within electric displacement vs. electric field hysteresis loops and the measured area was expressed in terms of an effective loss tangent. This approach matches the measured area within the hysteresis loop to an equivalent area ellipse in which the electric displacement lags the electric field by an amount, delta, under sinusoidal loading. The results collapse the measured loss as a function of bias stress and electric field amplitude reasonably close to a single curve. The measured dielectric loss behavior was attributed to the compressive stress preload driving a partial phase transformation from rhombohedral to orthorhombic and the electric field driving the reverse phase transformation from the stress induced orthorhombic phase to the zero stress rhombohedral phase. When the compressive bias stress partially or fully drives this phase transformation, the dielectric loss under unipolar electric field loading increases. This work is focused on quasi-static measurements. The large field dielectric loss is anticipated to be a function of frequency and temperature.

  4. Fabrication of graphene field-effect transistor on top of ferroelectric single-crystal substrate

    NASA Astrophysics Data System (ADS)

    Park, Nahee; Kang, Haeyong; Lee, Yourack; Kim, Jeong-Gyun; Kim, Joong-Gyu; Yun, Yoojoo; Park, Jeongmin; Kim, Taesoo; Kim, Jung Ho; Jin, Youngjo; Shin, Yong Seon; Lee, Young Hee; Suh, Dongseok

    2015-03-01

    In the analysis of Graphene field-effect transistor, the substrate material which has the direct contact with Graphene layer plays an important in the device performance. In this presentation, we have tested PMN-PT(i.e.(1-x)Pb(Mg1/3Nb2/3) O3-xPbTiO3) substrate as a gate dielectric of Graphene field-effect transistor. Unlike the case of previously used substrates such as silicon oxide or hexagonal Boron-Nitride(h-BN), the PMN-PT substrate can induce giant amount of surface charge that is directly injected to the attached Graphene layer due to its ferroelectric property. And the hysteresis of polarization versus electric field of PMN-PT can cause the device to show the ferroelectric nonvolatile memory operation. We had successfully fabricated Graphene field-effect transistor using the mechanically exfoliated Graphene layer transferred on the PMN-PT(001) substrate. Unlike the case of mechanical exfoliation on the surface of silicon-oxide or the Poly(methyl methacrylate) (PMMA), the weak adhesion properties between graphene and PMNPT required the pretreatment on PMMA before the exfoliation process. The device performance is analyzed in terms of the effect of ferro- and piezo-electric effect of PMNPT substrate.

  5. Correlation between impurity distribution and location of ferroelectric domain walls in Nd : Mg : LiNbO 3 single crystal

    NASA Astrophysics Data System (ADS)

    Naumova, I. I.; Evlanova, N. F.; Blokhin, S. A.; Lavrishchev, S. V.

    1998-04-01

    Using selective chemical etching, scanning electron microscope (SEM) and wave dispersive X-ray (WDX) microanalysis we showed that the ferroelectric domain walls coincide with the maxima and minima Nd-impurity modulation in a periodically poled Nd : Mg : LiNbO 3 crystal grown by the Czochralski method along the normal to the (0 1 1¯ 2) face. Asymmetric form of the Nd-modulation produces nonequal positive and negative domains for one period. Variations of instantaneous rate of growth were estimated for facet and nonfacet crystal region in the framework of Burton-Prim-Slichter theory.

  6. Quantum paraelectricity coexisting with a ferroelectric metastable state in single crystals of NaNbO(3): a new quantum effect.

    PubMed

    Raevskaya, S I; Raevski, I P; Kubrin, S P; Panchelyuga, M S; Smotrakov, V G; Eremkin, V V; Prosandeev, S A

    2008-06-11

    We experimentally show that, in contrast to the data having been collected so far, some single crystals of NaNbO(3) exhibit a dielectric permittivity of several thousand, at low T, and this value is saturated when approaching 0 K on cooling. Other sodium niobate crystals (having larger dielectric losses) present a first-order phase transition to a ferroelectric phase on cooling (at 80-200 K). The width of the thermal hysteresis in these crystals increases when the temperature of the phase transition obtained on heating decreases. The dielectric permittivity at the phase transition obtained on cooling shows a tendency to increase and saturate, when the thermal hysteresis increases. We identify the ground state of the sodium niobate crystal exhibiting the smallest dielectric losses (in the studied set of crystals) as a novel quantum paraelectric state coexisting with a metastable ferroelectric state. In principle, the crystal presenting the state of quantum paraelectricity can be considered as having the largest (among the crystals studied) thermal hysteresis, for which the low boundary is below 0 K.

  7. Photorefractive effect in ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Sasaki, Takeo; Naka, Yumiko

    2014-03-01

    In this paper, we review recent progress of research on the photorefractive effect of ferroelectric liquid crystals. The photorefractive effect is a phenomenon that forms a dynamic hologram in a material. The interference of two laser beams in a photorefractive material establishes a refractive index grating. This phenomenon is applicable to a wide range of devices related to diffraction optics including 3D displays, optical amplification, optical tomography, novelty filters, and phase conjugate wave generators. Ferroelectric liquid crystals are considered as a candidate for practical photorefractive materials. A refractive index grating formation time of 8-10 ms and a large gain coefficient are easily obtained in photorefractive ferroelectric liquid crystals.

  8. Photoluminescence and electrical properties of Eu-doped (Na0.5Bi0.5)TiO3 ferroelectric single crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Haiwu; Zhao, Xiangyong; Deng, Hao; Chen, Chao; Lin, Di; Li, Xiaobing; Yan, Jun; Luo, Haosu

    2014-02-01

    Eu3+-doped Na0.5Bi0.5TiO3 (Eu:NBT) single crystals were grown by a top-seeded solution growth method. Photoluminescence emission and excitation spectra of Eu:NBT were investigated. The two transitions in 7F0 → 5D0 excitation spectra reveal that Eu3+ ions were incorporated into two adjacent crystallographic sites in NBT, i.e., Bi3+ and Na+ sites. The former has a symmetrical surrounding, while the later has a disordered environment, which was confirmed by decay curve measurements. The dielectric dispersion behavior was depressed and the piezoelectric and ferroelectric properties were improved after Eu doping.

  9. Direct laser-writing of ferroelectric single-crystal waveguide architectures in glass for 3D integrated optics

    PubMed Central

    Stone, Adam; Jain, Himanshu; Dierolf, Volkmar; Sakakura, Masaaki; Shimotsuma, Yasuhiko; Miura, Kiyotaka; Hirao, Kazuyuki; Lapointe, Jerome; Kashyap, Raman

    2015-01-01

    Direct three-dimensional laser writing of amorphous waveguides inside glass has been studied intensely as an attractive route for fabricating photonic integrated circuits. However, achieving essential nonlinear-optic functionality in such devices will also require the ability to create high-quality single-crystal waveguides. Femtosecond laser irradiation is capable of crystallizing glass in 3D, but producing optical-quality single-crystal structures suitable for waveguiding poses unique challenges that are unprecedented in the field of crystal growth. In this work, we use a high angular-resolution electron diffraction method to obtain the first conclusive confirmation that uniform single crystals can be grown inside glass by femtosecond laser writing under optimized conditions. We confirm waveguiding capability and present the first quantitative measurement of power transmission through a laser-written crystal-in-glass waveguide, yielding loss of 2.64 dB/cm at 1530 nm. We demonstrate uniformity of the crystal cross-section down the length of the waveguide and quantify its birefringence. Finally, as a proof-of-concept for patterning more complex device geometries, we demonstrate the use of dynamic phase modulation to grow symmetric crystal junctions with single-pass writing. PMID:25988599

  10. Phase transitions and thermal-stress-induced structural changes in a ferroelectric Pb (Zr0.80Ti0. 20)O3 single crystal

    DOE PAGES

    Frantti, Johannes; Fujioka, Y.; Puretzky, Alexander A.; ...

    2014-12-22

    Zirconium-rich lead-zirconate-titanate (PZT) Pb(Zr0.80Ti0.20)O3 single crystal is studied by polarized-Raman scattering experiments as a function of temperature. We show that the crystal possesses complex domain boundaries which show no sign of instability even 200 K above the ferroelectric-to-paraelectric phase transition. The boundary stabilized the domains which had the same orientation after cyclic heating and cooling up to 773 K. The domains transformed normally to the cubic paraelectric phase, but returned to their original state after cooling. Physical mechanism behind the reversible behavior is related to the strain between the boundary region and domain, which forces the domain to grow similarlymore » after each heating and cooling cycle. Electron backscattering diffraction measurements show that macroscopic domains, lengths scale in hundreds of microns, are divided into regions whose Pb-displacements are not correlated. The results are notably interesting for non-volatile memory development as it implies that the original ferroelectric state can be restored after the material has been transformed to a paraelectric phase. Incoherent Pbdisplacements play a role for polarization switching.« less

  11. An I-integral method for crack-tip intensity factor variation due to domain switching in ferroelectric single-crystals

    NASA Astrophysics Data System (ADS)

    Yu, Hongjun; Wang, Jie; Shimada, Takahiro; Wu, Huaping; Wu, Linzhi; Kuna, Meinhard; Kitamura, Takayuki

    2016-09-01

    In the present study, an I-integral method is established for solving the crack-tip intensity factors of ferroelectric single-crystals. The I-integral combined with the phase field model is successfully used to investigate crack-tip intensity factor variations due to domain switching in ferroelectricity subjected to electromechanical loadings, which exhibits several advantages over previous methods based on small-scale switching. First, the shape of the switching zone around a crack tip is predicted by the time-dependent Ginzburg-Landau equation, which does not require preset energy-based switching criterion. Second, the I-integral can directly solve the crack-tip intensity factors and decouple the crack-tip intensity factors of different modes based on superimposing an auxiliary state onto an actual state. Third, the I-integral is area-independent, namely, the I-integral is not affected by the integral area size, the polarization distributions, or domain walls. This makes the I-integral applicable to large-scale domain switching. To this end, the electro-elastic field intensity factors of an impermeable crack in PbTiO3 ferroelectric single crystals are evaluated under electrical, mechanical, and combined loading. The intensity factors obtained by the I-integral agree well with those obtained by the extrapolation technique. From numerical results, the following conclusions can be drawn with respect to fracture behavior of ferroelectrics under large-scale switching. Under displacement controlled mechanical loading, the stress intensity factors (SIFs) decrease monotonically due to the domain switching process, which means a crack tip shielding or effective switching-induced toughening occurs. If an external electric field is applied, the electric displacement intensity factor (EDIF) increases in all cases, i.e., the formed domain patterns enhance the electric crack tip loading. The energy release rate, expressed by the crack-tip J-integral, is reduced by the domain

  12. Precursor polar clusters in the paraelectric phase of ferroelectric Ba₀.₈₀Ca₀.₂₀TiO₃ single crystals studied by Brillouin light scattering.

    PubMed

    Kim, Tae Hyun; Kojima, Seiji; Park, Kibog; Kim, Sung Baek; Ko, Jae-Hyeon

    2010-06-09

    A strong relaxation mode was observed in the gigahertz frequency window in the paraelectric phase of Ba₀.₈₀Ca₀.₂₀TiO₃ single crystals by using Brillouin light scattering. The appearance and growth of this relaxation mode were accompanied by substantial softening of the longitudinal acoustic mode as well as a remarkable increase in the hypersonic damping. Similar to BaTiO₃, the temperature dependence of the relaxation time of Ba₀.₈₀Ca₀.₂₀TiO₃ displayed a slowing-down behavior near the Curie temperature, indicating the order-disorder nature of the paraelectric-ferroelectric phase transition in this substance. The dynamics of precursor polar clusters observed in this work was discussed in relation with recent theoretical studies and found to be consistent with their predictions.

  13. Ferroelectric, Thermal, and Magnetic Characteristics of Praseodymium Malonate Hexahydrate Crystals

    NASA Astrophysics Data System (ADS)

    Ahmad, Nazir; Ahmad, M. M.; Kotru, P. N.

    2016-04-01

    Gel-grown single crystals of [Pr2(C3H2O4)3(H2O)6] exhibit remarkably flat habit faces, the most predominant being {110}. High-resolution x-ray diffraction analysis showed that the crystals are free from structural grain boundaries, which is the key requirement for single crystals for use in the microelectronics industry to serve as low-dielectric-constant ferroelectric material. The dielectric behavior recorded on {110} planes of single crystals shows that the crystal is ferroelectric with transition temperature T c = 135°C, which differs from the Curie-Weiss temperature T 0 by 2°C (T 0 < T c). Material in pellet form is shown to exhibit slightly different dielectric behavior. Polarization versus electric field confirms the ferroelectric behavior of the material. The dielectric behavior is also supported by the results of thermal studies, viz. thermogravimetric analysis (TGA), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The magnetic susceptibility and magnetic moment are calculated to be 30.045 × 10-6 emu and 3.092 BM, respectively.

  14. Phase-field modeling of ferroelectric to paraelectric phase boundary structures in single-crystal barium titanate

    NASA Astrophysics Data System (ADS)

    Woldman, Alexandra Y.; Landis, Chad M.

    2016-03-01

    Ferroelectric perovskite materials have been shown to exhibit a large electrocaloric effect near phase transitions. We develop a computational model based on a phase-field approach to characterize the structure of ferroelectric to paraelectric phase boundaries for planar configurations under generalized plane strain with temperatures near the Curie temperature. A nonlinear finite element method is used to solve for the phase boundary structure of a representative unit cell with a 180° ferroelectric laminate for a range of domain widths. The temperature at which the phase boundary can be found increases with domain width, approaching the Curie temperature asymptotically. The excess free energy density per unit area of the boundary increases with domain width. As expected, closure domains form between the ferroelectric and paraelectric phase, and the shape of the closure domains evolves from triangular to needle-shaped as the domain width increases. The entropy jump across the phase boundary is quantified and is shown to increase with domain width as well. A planar configuration with a 90° ferroelectric laminate is investigated, but shown to be physically unlikely due to the high stress levels required to achieve strain compatibility between the phases. Possible three-dimensional structures of the ferroelectric-paraelectric phase boundary are also discussed.

  15. Collective and molecular relaxation in ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Wrobel, S.; Marzec, M.; Godlewska, Malgorzata; Gestblom, B.; Hiller, Steffen; Haase, Wolfgang

    1995-08-01

    Ferroelectric liquid crystals are molecular ferroelectrics showing up in the tilted liquid crystalline systems (SmC*, SmI*, SmF*) composed of chiral molecules. In this work, we present the dielectric, electro-optic, and calorimetric studies of a single component system: 3-octyloxy-6[2-fluor-4-(2-fluoroctyloxy)phenyl]-pyridine showing interesting ferroelectric properties. The compound exhibits a first order N*- SmC* phase transition which leads to a qualitatively new behavior, for instance the relaxation frequency of the soft mode below TC seems to be temperature independent. The high frequency relaxation process, connected with the reorientation around the long axis, is practically undisturbed at the N*-SmC* transition. Yet, it was found that in the SmC* phase, the best fit was obatined with two Cole-Cole functions yielding two relaxation times to describe a biased reorientation of molecules in the SmC* phase.

  16. Super-crystals in composite ferroelectrics

    PubMed Central

    Pierangeli, D.; Ferraro, M.; Di Mei, F.; Di Domenico, G.; de Oliveira, C. E. M.; Agranat, A. J.; DelRe, E.

    2016-01-01

    As atoms and molecules condense to form solids, a crystalline state can emerge with its highly ordered geometry and subnanometric lattice constant. In some physical systems, such as ferroelectric perovskites, a perfect crystalline structure forms even when the condensing substances are non-stoichiometric. The resulting solids have compositional disorder and complex macroscopic properties, such as giant susceptibilities and non-ergodicity. Here, we observe the spontaneous formation of a cubic structure in composite ferroelectric potassium–lithium–tantalate–niobate with micrometric lattice constant, 104 times larger than that of the underlying perovskite lattice. The 3D effect is observed in specifically designed samples in which the substitutional mixture varies periodically along one specific crystal axis. Laser propagation indicates a coherent polarization super-crystal that produces an optical X-ray diffractometry, an ordered mesoscopic state of matter with important implications for critical phenomena and applications in miniaturized 3D optical technologies. PMID:26907725

  17. Ferromagnetic and ferroelectric nanoparticles in liquid crystals

    NASA Astrophysics Data System (ADS)

    Reznikov, Yuriy; Glushchenko, Anatoliy; Garbovskiy, Yuriy

    This chapter introduces the basic principles of physics of magnetic and ferroelectric nanoparticles suspensions in thermotropic liquid crystals (LCs). It also covers the main features of such suspensions along with the look at the challenges that researchers in the field are facing today. Special attention is paid to understanding of major physical mechanisms responsible for the inuence of nanoparticles on the properties of LCs. In the case of magnetic nanoparticles, their dipole moments are aligned by an external magnetic field that, in turn, results in a reorientation of the LC due to the surface anchoring between the nanoparticles and the LC. This mechanical coupling between the LC and the magnetic particles determines the unique sensitivity of the suspension to magnetic fields. In regard to the ferroelectric particles, their effect on LCs is due to a strong electric field by the permanent electric dipoles of the particles. This field is strong enough to change the orientational ordering of the LC surrounding the particle. In addition, the above-mentioned mechanism of the surface anchoring may also take place. The ongoing scientific and technological problems related to the suspensions are discussed. Among such problems are the stability of the suspensions, selection of the proper surfactants, formation of the particle chains, and the effect of the electric charges on the properties of the ferroelectric liquid crystal suspensions.

  18. Effect of doping with Nd{sup 3+} ions on the structural and ferroelectric properties of Ca{sub 0.28}Ba{sub 0.72}Nb{sub 2}O{sub 6} single crystal

    SciTech Connect

    Gao, W.L.; Zhang, H.J.; Xia, S.Q.; Huang, B.B.; Liu, D.; Wang, J.Y.; Jiang, M.H.; Zheng, L.M.; Wang, J.F.; Lu, C.J.

    2010-09-15

    The crystal structure of Ca{sub 0.28}Ba{sub 0.72}Nb{sub 2}O{sub 6} (CBN-28) crystal with Nd-doping has been determined from X-ray single crystal diffraction data, in the tetragonal system with space group P4bm and the following parameters: a = b = 12.458 A, c = 3.954 A, V = 613.688 A{sup 3}, and Z = 5. X-ray diffraction results on a Nd-doped CBN-28 single crystal also have demonstrated that Nd{sup 3+} and Ca{sup 2+} occupy the same site in the crystal structure. Dielectric and ferroelectric measurements have been performed. Transition from ferroelectric to paraelectric at around 223 {sup o}C has been observed. The Nd-doped crystal has a lower Curie temperature (T{sub m}) than that of undoped CBN-28 crystal. The spontaneous polarization (P{sub s}) and coercive electric field (E{sub c}) also decrease compared with their values in the undoped CBN-28 crystal.

  19. The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals

    PubMed Central

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R.; Chen, Long-Qing

    2016-01-01

    The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50–80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials. PMID:27991504

  20. The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals

    NASA Astrophysics Data System (ADS)

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R.; Chen, Long-Qing

    2016-12-01

    The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50-80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials.

  1. The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals

    SciTech Connect

    Li, Fei; Zhang, Shujun; Yang, Tiannan; Xu, Zhuo; Zhang, Nan; Liu, Gang; Wang, Jianjun; Wang, Jianli; Cheng, Zhenxiang; Ye, Zuo-Guang; Luo, Jun; Shrout, Thomas R.; Chen, Long-Qing

    2016-12-19

    The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50–80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials.

  2. Ferroelectric Liquid Crystals In Aerodynamic Testing

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S.; Holmes, Harlan K.

    1994-01-01

    The process of simultaneous optical visualization and quantitative measurement of aerodynamic boundary layer parameters requires new concepts, materials and utilization methods. Measurement of shear stress in terms of the transmitted or the reflected light intensity from an aligned ferroelectric liquid crystal (FLC) thin (approx. 1 micron) film deposited on a glass substrate has been the first step in this direction. In this paper, recent progress in utilization of FLC thin films for skin friction measurement and for studying the state of the boundary layer in a wind tunnel environment is reviewed. The switching characteristics of FLCs have been used to measure pressure from the newly devised system of partially exposed polymer dispersed ferroelectric liquid crystals (PEPDFLCs). In this configuration, a PEPDFLC thin film (approx. 10-25 microns) is sandwiched between two transparent conducting electrodes, one a rigid surface and the other a flexible sheet such as polyvinylidene fluoride or mylar. The switching characteristics of the film are a function of the pressure applied to the flexible transparent electrode and a predetermined bias voltage across the two electrodes. The results, considering the dielectrics of composite media, are discussed.

  3. Topology and temperature dependence of the diffuse X-ray scattering in Na0.5Bi0.5TiO3 ferroelectric single crystals.

    PubMed

    Gorfman, Semën; Keeble, Dean S; Bombardi, Alessandro; Thomas, Pam A

    2015-10-01

    The results of high-resolution measurements of the diffuse X-ray scattering produced by a perovskite-based Na0.5Bi0.5TiO3 ferroelectric single crystal between 40 and 620 K are reported. The study was designed as an attempt to resolve numerous controversies regarding the average structure of Na0.5Bi0.5TiO3, such as the mechanism of the phase transitions between the tetragonal, P4bm, and rhombohedral | monoclinic, R3c | Cc, space groups and the correlation between structural changes and macroscopic physical properties. The starting point was to search for any transformations of structural disorder in the temperature range of thermal depoling (420-480 K), where the average structure is known to remain unchanged. The intensity distribution around the {032} pseudocubic reflection was collected using a PILATUS 100K detector at the I16 beamline of the Diamond Light Source (UK). The data revealed previously unknown features of the diffuse scattering, including a system of dual asymmetric L-shaped diffuse scattering streaks. The topology, temperature dependence, and relationship between Bragg and diffuse intensities suggest the presence of complex microstructure in the low-temperature R3c | Cc phase. This microstructure may be formed by the persistence of the higher-temperature P4bm phase, built into a lower-temperature R3c | Cc matrix, accompanied by the related long-range strain fields. Finally, it is shown that a correlation between the temperature dependence of the X-ray scattering features and the temperature regime of thermal depoling is present.

  4. Structure and properties of Bi(Zn0.5Ti0.5)O3- Pb(Zr(1-x)Ti(x))O3 ferroelectric single crystals grown by a top-seeded solution growth technique.

    PubMed

    Wang, Bixia; Wu, Xiaoqing; Ren, Wei; Ye, Zuo-Guang

    2015-06-01

    Bi(Zn0.5Ti0.5)O3 (BZT)-modified Pb(Zr(1-x)Ti(x))O3 (PZT) single crystals have been grown using a top-seeded solution growth technique and characterized by various methods. The crystal structure is found to be rhombohedral by means of X-ray powder diffraction. The composition and homogeneity of the as-grown single crystals are studied by laser ablation inductively coupled plasma mass spectrometry and X-ray photoelectron spectroscopy. The domain structure of a (001)(cub) platelet is investigated by polarized light microscopy (PLM), which confirms the rhombohedral symmetry. The paraelectric-to-ferroelectric phase transition temperature T(C) is found to be 313°C with the absence of rhombohedral-tetragonal phase transition. The ferroelectric properties of the ternary crystals are enhanced by the BZT substitution with a remanent polarization of 28 μC/cm(2) and a coercive field E(C) of 22.1 kV/cm.

  5. Fork gratings based on ferroelectric liquid crystals.

    PubMed

    Ma, Y; Wei, B Y; Shi, L Y; Srivastava, A K; Chigrinov, V G; Kwok, H-S; Hu, W; Lu, Y Q

    2016-03-21

    In this article, we disclose a fork grating (FG) based on the photo-aligned ferroelectric liquid crystal (FLC). The Digital Micro-mirror Device based system is used as a dynamic photomask to generated different holograms. Because of controlled anchoring energy, the photo alignment process offers optimal conditions for the multi-domain FLC alignment. Two different electro-optical modes namely DIFF/TRANS and DIFF/OFF switchable modes have been proposed where the diffraction can be switched either to no diffraction or to a completely black state, respectively. The FLC FG shows high diffraction efficiency and fast response time of 50µs that is relatively faster than existing technologies. Thus, the FLC FG may pave a good foundation toward optical vertices generation and manipulation that could find applications in a variety of devices.

  6. Chiralization and ferroelectric state induction in nanostructured liquid crystals

    NASA Astrophysics Data System (ADS)

    Katranchev, B.; Petrov, M.; Rafailov, P. M.; Todorov, N.

    2016-02-01

    The liquid crystals (LC), due to their naturally high bulk ordering, strong birefringence and easy electrooptical driving, serve as matrix in the nanocomposites doped with non-mesogenic or mesogenic nanoparticles. The nanocomposite's structural units exhibit very complex molecular form indicating the strength and the intermolecular interaction between the matrix and dopant's molecules. Hydrogen bonds are of particular significance for the formation of the nanocomposite structural units, since the symmetry of the LC nanocomposite could be controlled and controllably decreased due to the acceptor-donor interaction between the dimeric matrix and the dopants. As a result, the LC nanocomposite can reach the lowest symmetry, known as triclinic - C1. Using the LC p,n-alkyloxybensoic acids (nOBA) in form of hydrogen-bonded dimers as matrix and non-mesogenics - single walls carbon nanotubes (SWCNT), perfluorooctanoic acid (PFOA), 4-hydrooxypiridin (HOPY) or mesogen - cholesteryl benzoate (ChB) as dopants and choosing optimal concentrations (where the typical LC state was preserved), we obtained nanocomopsites 7OBA/SWCNT, 7OBA/PFOA, 9OBA/HOPY and 8OBA/ChB. We indicate two forms of ferroelectricity in the studied nanocomposites: developable ferroelectricity, characteristic for the 9OBA/HOPY, 7OBA/PFOA compounds and developed ferroelectricity characteristic for 8OBA/SWCNT, 8OBA/ChB.

  7. Relaxor Ferroelectrics: Back to the Single-Soft-Mode Picture

    NASA Astrophysics Data System (ADS)

    Hehlen, B.; Al-Sabbagh, M.; Al-Zein, A.; Hlinka, J.

    2016-10-01

    The fluctuations of electric polarization in a disordered ferroelectric substance, relaxor crystal PbMg1 /3Nb2 /3O3 (PMN), were studied using a nonlinear inelastic light-scattering technique, hyper-Raman scattering, within a 5 - 100 cm-1 spectral interval and in a broad temperature range from 20 to 900 K. The split ferroelectric mode reveals a local anisotropy of up to about 400 K. Spectral anomalies observed at higher temperatures are explained as due to avoided crossing of the single primary polar soft mode with a temperature-independent, nonpolar spectral feature near 45 cm-1 , known from Raman scattering. The temperature changes of the vibrational modes involved in the measured fluctuation spectra of PMN were captured in a simple model that accounts for the temperature dependence of the dielectric permittivity as well. The observed slowing down of the relaxational dynamics directly correlates with the huge increase of the dielectric permittivity.

  8. Relaxation Dynamics of Ferroelectric Liquid Crystals in Pulsed Electric Field

    NASA Astrophysics Data System (ADS)

    Kudreyko, A. A.; Migranov, N. G.; Migranova, D. N.

    2016-11-01

    In this contribution we report a theoretical study of relaxation processes in surface-stabilized ferroelectric liquid crystals with spontaneous polarization. The influence of pulsed electric field on the behavior of ferroelectric liquid crystal in the SmC* phase, which is placed in a thin cell with strong anchoring of SmC* molecules with the boundary substrate, is studied. In the vicinity of the substrate interface, temporal dependence of the azimuthal motion of the director induced by electric field is obtained. The response to the external distortion of ferroelectric liquid crystal confined between two microstructured substrates is the occurrence of periodic temporal formation of solitons connected with the distortion of the director field n in the sample bulk. The interplay between microstructured substrates and director distribution of the ferroelectric SmC* phase is explained by the Frenkel-Kontorova model for a chain of atoms, but adapted for the continuum problem.

  9. Novel ferroelectric single crystals of Bi(Zn{sub 1/2}Ti{sub 1/2})O{sub 3}-PbZrO{sub 3}-PbTiO{sub 3} ternary solid solution

    SciTech Connect

    Wang, Bixia; Xie, Yujuan; Zhuang, Jian; Wu, Xiaoqing; Ren, Wei; Ye, Zuo-Guang

    2014-02-28

    Ferroelectric single crystals of a new lead-reduced Bi(Zn{sub 1/2}Ti{sub 1/2})O{sub 3}-PbZrO{sub 3}-PbTiO{sub 3} (BZT-PZ-PT) ternary solid solution system have been grown for the first time by three different methods, namely high temperature solution growth (HTSG, or flux method), top-cooled solution growth (TCSG), and top-seeded solution growth (TSSG). The chemical and thermodynamic parameters, including the flux concentration, the soaking temperature and the cooling rate, have been optimized, leading to the growth of good quality BZT-PZ-PT crystals of pseudo-cubic morphology. A large size crystal of the dimensions of 2 × 2 × 0.5 cm{sup 3} has been obtained by the TSSG technique. The crystal structure is analyzed by means of X-ray powder diffraction. The highest ferroelectric Curie temperature T{sub C} of the grown crystals is found to be 320 °C by means of dielectric measurements. A remnant polarization of 32 μC/cm{sup 2} is displayed with a coercive field of 15.4 kV/cm. The high T{sub C} and large coercive field of the BZT-PZ-PT single crystal make this material a promising candidate for applications in high power electromechanical transducers that can operate in a wider temperature range and at high fields.

  10. Phononic Crystal Tunable via Ferroelectric Phase Transition

    NASA Astrophysics Data System (ADS)

    Xu, Chaowei; Cai, Feiyan; Xie, Shuhong; Li, Fei; Sun, Rong; Fu, Xianzhu; Xiong, Rengen; Zhang, Yi; Zheng, Hairong; Li, Jiangyu

    2015-09-01

    Phononic crystals (PCs) consisting of periodic materials with different acoustic properties have potential applications in functional devices. To realize more smart functions, it is desirable to actively control the properties of PCs on demand, ideally within the same fabricated system. Here, we report a tunable PC made of Ba0.7Sr0.3Ti O3 (BST) ceramics, wherein a 20-K temperature change near room temperature results in a 20% frequency shift in the transmission spectra induced by a ferroelectric phase transition. The tunability phenomenon is attributed to the structure-induced resonant excitation of A0 and A1 Lamb modes that exist intrinsically in the uniform BST plate, while these Lamb modes are sensitive to the elastic properties of the plate and can be modulated by temperature in a BST plate around the Curie temperature. The study finds opportunities for creating tunable PCs and enables smart temperature-tuned devices such as the Lamb wave filter or sensor.

  11. Thermally tunable ferroelectric thin film photonic crystals.

    SciTech Connect

    Lin, P. T.; Wessels, B. W.; Imre, A.; Ocola, L. E.; Northwestern Univ.

    2008-01-01

    Thermally tunable PhCs are fabricated from ferroelectric thin films. Photonic band structure and temperature dependent diffraction are calculated by FDTD. 50% intensity modulation is demonstrated experimentally. This device has potential in active ultra-compact optical circuits.

  12. Phase transitions and thermal-stress-induced structural changes in a ferroelectric Pb (Zr0.80Ti0. 20)O3 single crystal

    SciTech Connect

    Frantti, Johannes; Fujioka, Y.; Puretzky, Alexander A.; Xie, Y; Ye, Z. -G.; Parish, Chad M.; Glazer, A. M.

    2014-12-22

    Zirconium-rich lead-zirconate-titanate (PZT) Pb(Zr0.80Ti0.20)O3 single crystal is studied by polarized-Raman scattering experiments as a function of temperature. We show that the crystal possesses complex domain boundaries which show no sign of instability even 200 K above the ferroelectric-to-paraelectric phase transition. The boundary stabilized the domains which had the same orientation after cyclic heating and cooling up to 773 K. The domains transformed normally to the cubic paraelectric phase, but returned to their original state after cooling. Physical mechanism behind the reversible behavior is related to the strain between the boundary region and domain, which forces the domain to grow similarly after each heating and cooling cycle. Electron backscattering diffraction measurements show that macroscopic domains, lengths scale in hundreds of microns, are divided into regions whose Pb-displacements are not correlated. The results are notably interesting for non-volatile memory development as it implies that the original ferroelectric state can be restored after the material has been transformed to a paraelectric phase. Incoherent Pbdisplacements play a role for polarization switching.

  13. Continuous cross-over from ferroelectric to relaxor state and piezoelectric properties of BaTiO{sub 3}-BaZrO{sub 3}-CaTiO{sub 3} single crystals

    SciTech Connect

    Benabdallah, F.; Veber, P. Prakasam, M.; Viraphong, O.; Maglione, M.; Shimamura, K.

    2014-04-14

    Optimal properties like piezoelectricity can be found in polarizable materials for which the structure changes sharply under small composition variations in the vicinity of their morphotropic phase boundary or the triple point in their isobaric temperature-composition phase diagram. In the latter, lead-free (Ba{sub 0.850}Ca{sub 0.150})(Ti{sub 0.900}Zr{sub 0.100})O{sub 3} ceramics exhibit outstanding piezoelectric coefficients. For the first time, we report the growth of piezoelectric lead-free single crystals in the BaTiO{sub 3}-BaZrO{sub 3}-CaTiO{sub 3} pseudo-ternary system. The stoichiometry control in the CaO-BaO-TiO{sub 2}-ZrO{sub 2} solid solution led to single crystals with various compositions ranging from (Ba{sub 0.857}Ca{sub 0.143})(Ti{sub 0.928}Zr{sub 0.072})O{sub 3} to (Ba{sub 0.953}Ca{sub 0.047})(Ti{sub 0.427}Zr{sub 0.573})O{sub 3}. We evidenced a continuous cross-over from a ferroelectric state at high titanium content to a relaxor one on increasing the zirconium content. Such a property tuning is rather seldom observed in lead-free ferroelectrics and confirms what was already reported for ceramics. Single crystal with (Ba{sub 0.838}Ca{sub 0.162})(Ti{sub 0.854}Zr{sub 0.146})O{sub 3} composition, which has been grown and oriented along [001] crystallographic direction, displayed electromechanical coefficients d{sub 31} and k{sub 31} of 93 pC.N{sup −1} and 0.18, respectively, near the room temperature (T = 305 K)

  14. Continuous cross-over from ferroelectric to relaxor state and piezoelectric properties of BaTiO3-BaZrO3-CaTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Benabdallah, F.; Veber, P.; Prakasam, M.; Viraphong, O.; Shimamura, K.; Maglione, M.

    2014-04-01

    Optimal properties like piezoelectricity can be found in polarizable materials for which the structure changes sharply under small composition variations in the vicinity of their morphotropic phase boundary or the triple point in their isobaric temperature-composition phase diagram. In the latter, lead-free (Ba0.850Ca0.150)(Ti0.900Zr0.100)O3 ceramics exhibit outstanding piezoelectric coefficients. For the first time, we report the growth of piezoelectric lead-free single crystals in the BaTiO3-BaZrO3-CaTiO3 pseudo-ternary system. The stoichiometry control in the CaO-BaO-TiO2-ZrO2 solid solution led to single crystals with various compositions ranging from (Ba0.857Ca0.143)(Ti0.928Zr0.072)O3 to (Ba0.953Ca0.047)(Ti0.427Zr0.573)O3. We evidenced a continuous cross-over from a ferroelectric state at high titanium content to a relaxor one on increasing the zirconium content. Such a property tuning is rather seldom observed in lead-free ferroelectrics and confirms what was already reported for ceramics. Single crystal with (Ba0.838Ca0.162)(Ti0.854Zr0.146)O3 composition, which has been grown and oriented along [001] crystallographic direction, displayed electromechanical coefficients d31 and k31 of 93 pC.N-1 and 0.18, respectively, near the room temperature (T = 305 K).

  15. Optical model of transient light scattering in ferroelectric liquid crystals

    SciTech Connect

    Loiko, V. A. Konkolovich, A. V.; Miskevich, A. A.

    2009-03-15

    A static optical model is developed for the effect of field-induced transient scattering on coherent light transmission through ferroelectric liquid crystals. Scattering processes are described by introducing an optically anisotropic medium containing scatterers (transient domains). The results presented in the paper are obtained for a plane parallel layer of ferroelectric liquid crystals with a planar helicoidal structure under normal illumination with a linearly polarized plane wave. An analysis is presented of the coherent transmittance of the layer in static applied electric fields.

  16. Large strain transduction utilizing phase transition in relaxor-ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Finkel, Peter; Benjamin, Kim; Amin, Ahmed

    2011-05-01

    In this work, we present experimental evidence that under relatively low level drive (<0.1 MV/m) the large strain (˜0.5%) associated with ferroelectric rhombohedral FR-ferroelectric orthorhombic FO phase transition in domain engineered relaxor-ferroelectric single crystals under compressive stress and bias electric field can be captured. We have demonstrated this in mechanically confined ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals poised at the rhombohedral side of the morphotropic phase boundary. Experimental strain-field results, methods of mechanical confinement and drive, and a low frequency, compact, high source level sound projector design are presented. Transducers that operate on a large strain principle as a design rule will benefit from this development.

  17. Ferroelectric Tungsten Bronze Bulk Crystals and Epitaxial Thin Films for Electro-Optic Device Applications

    DTIC Science & Technology

    1983-05-01

    23 FERROELECTRIC TUNGSTEN BRONZE BULK CRYSTALS AND EPITAXIAL THIN FILMS FOR ELECTRO-OPTIC DEVICE APPLICATIONS 10 CO O Semi-Annual Technical... THIN FILMS FOR ELECTRO-OPTIC DEVICE APPLICATIONS s TV^C or REPORT * pcmoo COVCHCO Semi-Annual Tec1! Rpt #1 for period 09/30/82-03/31/83...months, considerable progress has been made in several areas, including single crystal and thin film growth and characteriza- tion. The new

  18. Iminodiacetic acid doped ferroelectric triglycine sulphate crystal: Crystal growth and characterization

    NASA Astrophysics Data System (ADS)

    Rai, Chitharanjan; Narayana Moolya, B.; Dharmaprakash, S. M.

    2011-01-01

    Single crystals of iminodiacetic acid (HN(CH 2COOH) 2) doped triglycine sulphate (IDATGS) crystals have been grown from aqueous solution containing 1-10 mol% of iminodiacetic acid at constant temperature by slow evaporation technique. The effects of different amounts of doping entities on the growth habit have been investigated. X-ray powder diffraction pattern for pure and doped TGS was collected to determine the lattice parameters. The grown crystals were subjected to Fourier transform infrared (FTIR) spectroscopy studies to find the presence of various functional groups qualitatively. The dielectric permittivity has been studied as a function of temperature. An increase in the transition temperature (49.2-49.7 °C) of IDATGS crystals is observed. The dielectric constant ( ε‧ max) of IDATGS crystals vary in the range 922-2410 compared to pure TGS ( Tc=49.12 °C and ε‧ max=3050). Curie Weiss constants Cp and Cf in the paraelectric and ferroelectric phases were determined. The transition temperature ( Tc) is found to decrease with increase in dopant concentration. P- E hysteresis studies show the presence of internal bias field in the crystal. Piezoelectric measurements were also carried out at room temperature. Domain patterns on b-cut plates were observed using scanning electron microscope. The micro hardness studies reveal that the doped crystals are harder than the pure TGS crystals. The low dielectric constant, higher transition temperature, internal bias field and hardness suggest that IDATGS crystals could be a potential material for IR detectors.

  19. Design of ferroelectric organic molecular crystals with ultrahigh polarization.

    PubMed

    Chen, Shuang; Zeng, Xiao Cheng

    2014-04-30

    Inspired by recent successful synthesis of room-temperature ferroelectric supramolecular charge-transfer complexes, i.e., tetrathiafulvalene (TTF)- and pyromellitic diimide (PMDI)-based crystals (Tayi et al. Nature 2012, 488, 485-489), three new ferroelectric two-component organic molecular crystals are designed based on the TTF and PMDI motifs and an extensive polymorph search. To achieve energetically favorable packing structures for the crystals, a newly developed computational approach that combines polymorph predictor with density functional theory (DFT) geometry optimization is employed. Tens of thousands of packing structures for the TTF- and PMDI-based crystals are first generated based on the limited number of asymmetric units in a unit cell as well as limited common symmetry groups for organocarbon crystals. Subsequent filtering of these packing structures by comparing with the reference structures yields dozens of promising crystal structures. Further DFT optimizations allow us to identify several highly stable packing structures that possess the space group of P2₁ as well as high to ultrahigh spontaneous polarizations (23-127 μC/cm(2)) along the crystallographic b axis. These values are either comparable to or much higher than the computed value (25 μC/cm(2)) or measured value (55 μC/cm(2)) for the state-of-the-art organic supramolecular systems. The high polarization arises from the ionic displacement. We further construct surface models to derive the electric-field-switched low-symmetry structures of new TTF- and PMDI-based crystals. By comparing the high-symmetry and low-symmetry crystal structures, we find that the ferroelectric polarization of the crystals is very sensitive to atomic positions, and a small molecular displacement may result in relatively high polarizations along the a and c axes, polarity reversal, and/or electronic contribution to polarization. If these newly designed TTF- and PMDI-based crystals with high polarizations are

  20. Note: Laser beam scanning using a ferroelectric liquid crystal spatial light modulator

    SciTech Connect

    Das, Abhijit; Boruah, Bosanta R.

    2014-04-15

    In this work we describe laser beam scanning using a ferroelectric liquid crystal spatial light modulator. Commercially available ferroelectric liquid crystal spatial light modulators are capable of displaying 85 colored images in 1 s using a time dithering technique. Each colored image, in fact, comprises 24 single bit (black and white) images displayed sequentially. We have used each single bit image to write a binary phase hologram. For a collimated laser beam incident on the hologram, one of the diffracted beams can be made to travel along a user defined direction. We have constructed a beam scanner employing the above arrangement and demonstrated its use to scan a single laser beam in a laser scanning optical sectioning microscope setup.

  1. Frederiks transition in ferroelectric liquid-crystal nanosuspensions

    NASA Astrophysics Data System (ADS)

    Shelestiuk, Sergii M.; Reshetnyak, Victor Yu.; Sluckin, Timothy J.

    2011-04-01

    We construct a theoretical model of the dielectric properties of a ferroelectric LC nanosuspension (FLCNS), using a generalized Maxwell-Garnett picture. The theory supposes that an FLCNS may as a first approximation be considered as a complex homogeneous dielectric ceramic, thus neglecting positional correlations of the colloidal particles. The FLCNS then consists of an anisotropic matrix with a very low concentration (<1% by volume) of impurity particles. The impurity particles possess both shape and dielectric anisotropy, as well as a permanent electric polarization and strong liquid-crystal director anchoring on the particle surface. We show that the effective dielectric properties for capacitance properties and for effective liquid-crystal free energies do not coincide. We calculate the effect of doping a liquid crystal with ferroelectric impurities on the Frederiks transition. The theory takes account of inclusion shape, dielectric susceptibility, and local field effects. We neglect the possibility of dielectric particle chaining, which appears experimentally not to occur in general. Our calculations suggest, in qualitative agreement with experiment, that doping a nematic liquid crystal with ferroelectric particles, even at very low particle concentration, can in some cases significantly decrease the electric Frederiks threshold field.

  2. Waveguide formation mechanism generated by double doping in ferroelectric crystals

    NASA Astrophysics Data System (ADS)

    Atuchin, V. V.; Ziling, C. C.; Savatinova, I.; Armenise, M. N.; Passaro, V. M. N.

    1995-12-01

    Physical mechanisms causing the refractive index increase Δn in uniaxial oxidized ferroelectric crystals subjected to double doping are discussed. The analysis shows that the index changes of the two different dopants, ΔnA and ΔnB, are additive only if the corresponding changes of the spontaneous polarization are small. Ti indiffusion and proton exchange (TIPE) waveguides in LiNbO3 are considered as an example of the case when this condition is not fulfilled. The hydrogen-lithium substitution in such waveguides leads to a strong reduction of the spontaneous polarization of the virgin crystals and the final index change Δn is not a sum of ΔnA and ΔnB. A physical model is developed to explain light waveguiding in double-doped ferroelectric structures. Experimental data obtained for TIPE waveguides confirm the model.

  3. Highly efficient single frequency blue laser generation by second harmonic generation of infrared lasers using quasi phase matching in periodically poled ferroelectric crystals

    NASA Astrophysics Data System (ADS)

    Khademian, Ali

    Performance and reliability of solid state laser diodes in the IR region exceeds those in the visible and UV part of the light spectrum. Single frequency visible and UV laser diodes with higher than 500 mW power are not available commercially. However we successfully stabilized a multi-longitudinal mode IR laser to 860 mW single frequency. This means high efficiency harmonic generation using this laser can produce visible and UV laser light not available otherwise. In this study we examined three major leading nonlinear crystals: PPMgO:SLN, PPKTP and PPMgO:SLT to generate blue light by second harmonic generation. We achieved record high net conversion efficiencies 81.3% using PPMgO:SLT (˜500 mW out), and 81.1% using PPKTP (˜700 mW out). In both these cases an external resonance buildup cavity was used. We also studied a less complicated single pass waveguide configuration (guided waist size of ˜ 5 um compared to ˜60 um) to generate blue. With PPMgO:SLN we obtained net 40.4% and using PPKT net 6.8% (110mW and 10.1 mW respectively).

  4. Directionally tunable and mechanically deformable ferroelectric crystals from rotating polar globular ionic molecules

    NASA Astrophysics Data System (ADS)

    Harada, Jun; Shimojo, Takafumi; Oyamaguchi, Hideaki; Hasegawa, Hiroyuki; Takahashi, Yukihiro; Satomi, Koichiro; Suzuki, Yasutaka; Kawamata, Jun; Inabe, Tamotsu

    2016-10-01

    Ferroelectrics are used in a wide range of applications, including memory elements, capacitors and sensors. Recently, molecular ferroelectric crystals have attracted interest as viable alternatives to conventional ceramic ferroelectrics because of their solution processability and lack of toxicity. Here we show that a class of molecular compounds—known as plastic crystals—can exhibit ferroelectricity if the constituents are judiciously chosen from polar ionic molecules. The intrinsic features of plastic crystals, for example, the rotational motion of molecules and phase transitions with lattice-symmetry changes, provide the crystals with unique ferroelectric properties relative to those of conventional molecular crystals. This allows a flexible alteration of the polarization axis direction in a grown crystal by applying an electric field. Owing to the tunable nature of the crystal orientation, together with mechanical deformability, this type of molecular crystal represents an attractive functional material that could find use in a diverse range of applications.

  5. Structural and electronic properties of Diisopropylammonium bromide molecular ferroelectric crystal

    NASA Astrophysics Data System (ADS)

    Alsaad, A.; Qattan, I. A.; Ahmad, A. A.; Al-Aqtash, N.; Sabirianov, R. F.

    2015-10-01

    We report the results of ab-initio calculations based on Generalized Gradient Approximation (GGA) and hybrid functional (HSE06) of electronic band structure, density of states and partial density of states to get a deep insight into structural and electronic properties of P21 ferroelectric phase of Diisopropylammonium Bromide molecular crystal (DIPAB). We found that the optical band gap of the polar phase of DIPAB is ∼ 5 eV confirming it as a good dielectric. Examination of the density of states and partial density of states reveal that the valence band maximum is mainly composed of bromine 4p orbitals and the conduction band minimum is dominated by carbon 2p, carbon 2s, and nitrogen 2s orbitals. A unique aspect of P21 ferroelectric phase is the permanent dipole within the material. We found that P21 DIPAB has a spontaneous polarization of 22.64 consistent with recent findings which make it good candidate for the creation of ferroelectric tunneling junctions (FTJs) which have the potential to be used as memory devices.

  6. Polymer Alignment Behavior with Molecular Switching of Ferroelectric Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Murashige, Takeshi; Fujikake, Hideo; Sato, Hiroto; Kikuchi, Hiroshi; Kurita, Taiichiro; Sato, Fumio

    2007-01-01

    This paper describes the molecular alignment behavior of polymer networks with switching of a ferroelectric liquid crystal (FLC) in a molecularly aligned FLC/polymer composite film. The polymer alignment in the composite film, which was slowly formed by photopolymerization-induced phase separation of a heated nematic-phase solution of FLC and monomers, was observed by polarization Raman spectral microscopy. Raman peak intensities originating from the polymers were changed with those from the FLC, when the applied voltage polarity was changed. The trace patterns of the Raman peak intensity with in-plane rotation of the composite film indicated that the formed flexible polymers can follow FLC molecular switching.

  7. Room temperature ferroelectricity in one-dimensional single chain molecular magnets [{M(Δ)M(Λ)}(ox)2(phen)2]n (M = Fe and Mn)

    NASA Astrophysics Data System (ADS)

    Bhatt, Pramod; Mukadam, M. D.; Meena, S. S.; Mishra, S. K.; Mittal, R.; Sastry, P. U.; Mandal, B. P.; Yusuf, S. M.

    2017-03-01

    The ferroelectric materials are mainly focused on pure inorganic oxides; however, the organic molecule based materials have recently attracted great attention because of their multifunctional properties. The mixing of oxalate and phenanthroline ligands with metal ions (Fe or Mn) at room temperature followed by hydrothermal treatment results in the formation of one-dimensional single chain molecular magnets which exhibit room temperature dielectric and ferroelectric behavior. The compounds are chiral in nature, and exhibit a ferroelectric behavior, attributed to the polar point group C2, in which they crystallized. The compounds are also associated with a dielectric loss and thus a relaxation process. The observed electric dipole moment, essential for a ferroelectricity, has been understood quantitatively in terms of lattice distortions at two different lattice sites within the crystal structure. The studied single chain molecular magnetic materials with room temperature ferroelectric and dielectric properties could be of great technological importance in non-volatile memory elements, and high-performance insulators.

  8. Recent Developments on High Curie Temperature PIN-PMN-PT Ferroelectric Crystals.

    PubMed

    Zhang, Shujun; Li, Fei; Sherlock, Nevin P; Luo, Jun; Lee, Hyeong Jae; Xia, Ru; Meyer, Richard J; Hackenberger, Wesley; Shrout, Thomas R

    2011-03-01

    Pb(In(0.5)Nb(0.5))O(3)-Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PIN-PMN-PT) ferroelectric crystals attracted extensive attentions in last couple years, due to their higher usage temperatures range (> 30°C) and coercive fields (~5kV/cm), meanwhile maintaining similar electromechanical couplings (k(33)> 90%) and piezoelectric coefficients (d(33)~1500pC/N), when compared to their binary counterpart Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3). In this article, we reviewed recent developments on the PIN-PMN-PT single crystals, including the Bridgman crystal growth, dielectric, electromechanical, piezoelectric and ferroelectric behaviors as function of temperature and dc bias. Mechanical quality factor Q was studied as function of orientation and phase. Of particular interest is the dynamic strain, which related to the Q and d(33), was found to be improved when compared to binary system, exhibiting the potential usage of PIN-PMN-PT in high power application. Furthermore, PIN-PMN-PT crystals exhibit improved thickness dependent properties, due to their small domain size, being on the order of 1μm. Finally, the manganese acceptor dopant in the ternary crystals was investigated and discussed briefly in this paper.

  9. SYMMETRICAL LASER CRYSTALS.

    DTIC Science & Technology

    CRYSTAL GROWTH , SYMMETRY(CRYSTALLOGRAPHY), LASERS, SYNTHESIS, FERROELECTRIC CRYSTALS , FLUORESCENCE, IMPURITIES, BARIUM COMPOUNDS, ZIRCONATES...STRONTIUM COMPOUNDS, TITANATES, STANNATES, SAMARIUM, MANGANESE, REFRACTORY MATERIALS, OXIDES, SINGLE CRYSTALS .

  10. Direct writing of ferroelectric domains on strontium barium niobate crystals using focused ultraviolet laser light

    SciTech Connect

    Boes, Andreas; Crasto, Tristan; Steigerwald, Hendrik; Mitchell, Arnan; Wade, Scott; Frohnhaus, Jakob; Soergel, Elisabeth

    2013-09-30

    We report ferroelectric domain inversion in strontium barium niobate (SBN) single crystals by irradiating the surface locally with a strongly focused ultraviolet (UV) laser beam. The generated domains are investigated using piezoresponse force microscopy. We propose a simple model that allows predicting the domain width as a function of the irradiation intensity, which indeed applies for both SBN and LiNbO{sub 3}. Evidently, though fundamentally different, the domain structure of both SBN and LiNbO{sub 3} can be engineered through similar UV irradiation.

  11. Domain structures and dielectric properties resulting from tweed precursors of relaxor ferroelectric solid-solution single-crystal 24Pb(In1/2Nb1/2)O3-46Pb (Mg1/3Nb2/3)O3-30PbTio3.

    PubMed

    Yasuda, Naohiko; Nur Hidayah, Z A; Ohwa, Hidehiro; Tachi, Yoshihito; Yamashita, Yohachi

    2012-09-01

    The domain structures of poled and depoled lead-based relaxor ferroelectric solid-solution single-crystal 24Pb(In(1/2)Nb(1/2))O(3)-46Pb (Mg(1/3)Nb(2/3))O(3)-30PbTio(3) are studied by polarized light microscopy, piezoresponse force microscopy (PFM), scanning electron microscopy (SEM), and dielectric spectroscopy. The domain structures in the nonergodic relaxor state are found by PFM to consist of tweed structures resulting from random fields from the competition between ferroelectric and antiferroelectric distortion, and planar defects found by SEM are treated as dislocations associated with strain accommodation, resulting in superior piezoelectric properties. This domain structure is found to be connected with hierarchical domain structures.

  12. Soft memory in a ferroelectric nanoparticle-doped liquid crystal

    NASA Astrophysics Data System (ADS)

    Basu, Rajratan

    2014-02-01

    A small quantity of BaTiO3 ferroelectric nanoparticles (FNP) was doped in a liquid crystal (LC), and the LC + FNP hybrid was found to exhibit a nonvolatile electromechanical memory effect in the isotropic phase. The permanent dipole moment of the FNPs causes the LC molecule to form short-range pseudonematic domains surrounding the FNPs. The FNP-induced short-range orders become more prominent in the isotropic phase when the global nematic order is absent. These short-range domains, being anisotropic in nature, interact with an external electric field, exhibiting a Fréedericksz-type transition. When the field is turned off, these domains stay oriented, showing a hysteresis effect due to the absence of any long-range order and restoring forces in the isotropic phase. The hysteresis graph for this memory effect shows a significant pretransitional behavior on approaching the nematic phase from the isotropic phase.

  13. Analog switching in the nanocolloids of ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Kumar, Pradeep; Kishore, Avinash; Sinha, Aloka

    2016-06-01

    Nanoparticle (NP) dispersion in liquid crystals (LCs) results in significant changes in the physical properties of the existing LC mixtures. Two ferroelectric liquid crystals (FLCs), 5 F6T and 6 F6T , have been studied for analog switching. The 5 F6T sample is doped with titanium dioxide (T i O2) NPs of two different concentrations of the same average particle size and another FLC 6 F6T is systematically doped with barium titanate (B a T i O3) NPs of two different average particle sizes at the same concentration. The frequency and temperature dependence of the coercive voltage of FLC nanocolloids has been studied. The V-shaped switching was observed in the case of nano-doped FLCs. The value of inversion frequency for the 5 F6T +1.0 wt.% TiO2 doped sample is 30 Hz while it is 24 Hz for the 6 F6T +0.5 wt.% BaTiO3 (particle size 5-10 nm) doped sample. The conductivity measurements show that the conductivity of doped samples is higher than the conductivity of their parental FLCs and can be considered the main reason for the V-shaped switching in the FLC nanocolloids, which was initially absent in their parental FLCs.

  14. SINGLE CRYSTAL NEUTRON DIFFRACTION.

    SciTech Connect

    KOETZLE,T.F.

    2001-03-13

    Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

  15. Nanomechanics of Ferroelectric Thin Films and Heterostructures

    SciTech Connect

    Li, Yulan; Hu, Shenyang Y.; Chen , L.Q.

    2016-08-31

    The focus of this chapter is to provide basic concepts of how external strains/stresses altering ferroelectric property of a material and how to evaluate quantitatively the effect of strains/stresses on phase stability, domain structure, and material ferroelectric properties using the phase-field method. The chapter starts from a brief introduction of ferroelectrics and the Landau-Devinshire description of ferroelectric transitions and ferroelectric phases in a homogeneous ferroelectric single crystal. Due to the fact that ferroelectric transitions involve crystal structure change and domain formation, strains and stresses can be produced inside of the material if a ferroelectric transition occurs and it is confined. These strains and stresses affect in turn the domain structure and material ferroelectric properties. Therefore, ferroelectrics and strains/stresses are coupled to each other. The ferroelectric-mechanical coupling can be used to engineer the material ferroelectric properties by designing the phase and structure. The followed section elucidates calculations of the strains/stresses and elastic energy in a thin film containing a single domain, twinned domains to complicated multidomains constrained by its underlying substrate. Furthermore, a phase field model for predicting ferroelectric stable phases and domain structure in a thin film is presented. Examples of using substrate constraint and temperature to obtain interested ferroelectric domain structures in BaTiO3 films are demonstrated b phase field simulations.

  16. Note: High-power piezoelectric transformer fabricated with ternary relaxor ferroelectric Pb(Mg(1/3)Nb(2/3))O3-Pb(In(1/2)Nb(1/2))O3-PbTiO3 single crystal.

    PubMed

    Wang, Qing; Ma, Chuanguo; Wang, Feifei; Liu, Bao; Chen, Jianwei; Luo, Haosu; Wang, Tao; Shi, Wangzhou

    2016-03-01

    A plate-shaped piezoelectric transformer was designed and fabricated using ternary relaxor ferroelectric single crystal Pb(Mg(1/3)Nb(2/3))O3-Pb(In(1/2)Nb(1/2))O3-PbTiO3. Both the input and output sections utilized the transverse-extensional vibration mode. The frequency and load dependences of the electrical properties for the proposed transformer were systematically studied. Results indicated that under a matching load resistance of 14.9 kΩ, a maximum output power of 2.56 W was obtained with the temperature rise less than 5 °C. The corresponding power density reached up to 50 W/cm(3). This ternary single-crystal transformer had potential applications in compact-size converters requiring high power density.

  17. Note: High-power piezoelectric transformer fabricated with ternary relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-Pb(In1/2Nb1/2)O3-PbTiO3 single crystal

    NASA Astrophysics Data System (ADS)

    Wang, Qing; Ma, Chuanguo; Wang, Feifei; Liu, Bao; Chen, Jianwei; Luo, Haosu; Wang, Tao; Shi, Wangzhou

    2016-03-01

    A plate-shaped piezoelectric transformer was designed and fabricated using ternary relaxor ferroelectric single crystal Pb(Mg1/3Nb2/3)O3-Pb(In1/2Nb1/2)O3-PbTiO3. Both the input and output sections utilized the transverse-extensional vibration mode. The frequency and load dependences of the electrical properties for the proposed transformer were systematically studied. Results indicated that under a matching load resistance of 14.9 kΩ, a maximum output power of 2.56 W was obtained with the temperature rise less than 5 °C. The corresponding power density reached up to 50 W/cm3. This ternary single-crystal transformer had potential applications in compact-size converters requiring high power density.

  18. Freedericksz transition in smectic-A liquid crystals doped by ferroelectric nanoparticles

    NASA Astrophysics Data System (ADS)

    Poursamad, J. B.; Hallaji, T.

    2017-01-01

    The structure, orientation and physical properties of liquid crystals is significantly affected by doping of ferroic (ferromagnetic and ferroelectric) nanoparticles into liquid crystals. Behavior of these suspensions in external fields depends on anchoring energy, volume fraction of doped nanoparticles, and sign of dielectric anisotropy of liquid crystals as well as relative orientation of director and local polarization of nanoparticles. Here, the threshold voltage for molecular reorientation (Freedericksz transition) is estimated theoretically in smectic-A liquid crystals doped by spherical ferroelectric nanoparticles, near the smectic-A to smectic-C transition temperature taking into account local electric field effects. It is shown that the threshold voltage is decreased by doping ferroelectric nanoparticles into liquid crystals.

  19. Single crystals of chitosan.

    PubMed

    Cartier, N; Domard, A; Chanzy, H

    1990-10-01

    Lamellar single crystals of chitosan were prepared at 125 degrees C by adding ammonia to a low DP fraction of chitosan dissolved in water. The crystals gave sharp electron diffraction diagrams which could be indexed in an orthorhombic P2(1)2(1)2(1) unit cell with a = 8.07 A, b = 8.44 A, c = 10.34 A. The unit cell contained two anti-parallel chitosan chains and no water molecules. It was found that cellulose microfibrils from Valonia ventricosa could act as nuclei for inducing the crystallization of chitosan on cellulose. This produced a shish-kebab morphology.

  20. Ferroelectric order in liquid crystal phases of polar disk-shaped ellipsoids

    NASA Astrophysics Data System (ADS)

    Bose, Tushar Kanti; Saha, Jayashree

    2014-05-01

    The demonstration of a spontaneous macroscopic ferroelectric order in liquid phases in the absence of any long range positional order is considered an outstanding problem of both fundamental and technological interest. Recently, we reported that a system of polar achiral disklike ellipsoids can spontaneously exhibit a long searched ferroelectric nematic phase and a ferroelectric columnar phase with strong axial polarization. The major role is played by the dipolar interactions. The model system of interest consists of attractive-repulsive Gay-Berne oblate ellipsoids embedded with two parallel point dipoles positioned symmetrically on the equatorial plane of the ellipsoids. In the present work, we investigate in detail the profound effects of changing the separation between the two symmetrically placed dipoles and the strength of the dipoles upon the existence of different ferroelectric discotic liquid crystal phases via extensive off-lattice N-P-T Monte Carlo simulations. Ferroelectric biaxial phases are exhibited in addition to the uniaxial ferroelectric fluids where the phase biaxiality results from the dipolar interactions. The structures of all the ferroelectric configurations of interest are presented in detail. Simple phase diagrams are determined which include different polar and apolar discotic fluids generated by the system.

  1. Flexo- and piezo-electric polarization of smectic layers in ferroelectric and antiferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Kuczyński, W.; Hoffmann, J.; Dardas, D.; Nowicka, K.; Bielejewska, N.

    2015-11-01

    In this paper, we report on how flexoelectric and piezoelectric polarization components can be determined by a method based on simultaneous studies of dielectric and electrooptic properties of the chiral smectic liquid crystal in the regime of weak electric fields. As a rule, the measurements of spontaneous polarization are performed using switching experiments. The polarization measured in this way is not complete—it contains the piezoelectric component only. However, the knowledge of the entire local polarization of a single smectic layer is of great importance—it is necessary for correct determination of some material parameters, for instance elastic constants. Our experiments performed in a helical smectic mixture demonstrated that flexoelectric contribution to the local spontaneous polarization is significant in both ferroelectric and antiferroelectric phases. In the antiferroelectric phase, the flexoelectric polarization is less due to higher helical pitch.

  2. Advantages and Challenges of Relaxor-PbTiO3 Ferroelectric Crystals for Electroacoustic Transducers- A Review

    PubMed Central

    Zhang, Shujun; Li, Fei; Jiang, Xiaoning; Kim, Jinwook; Luo, Jun; Geng, Xuecang

    2014-01-01

    Relaxor-PbTiO3 (PT) based ferroelectric crystals with the perovskite structure have been investigated over the last few decades due to their ultrahigh piezoelectric coefficients (d33 > 1500 pC/N) and electromechanical coupling factors (k33 > 90%), far outperforming state-of-the-art ferroelectric polycrystalline Pb(Zr,Ti)O3 ceramics, and are at the forefront of advanced electroacoustic applications. In this review, the performance merits of relaxor-PT crystals in various electroacoustic devices are presented from a piezoelectric material viewpoint. Opportunities come from not only the ultrahigh properties, specifically coupling and piezoelectric coefficients, but through novel vibration modes and crystallographic/domain engineering. Figure of merits (FOMs) of crystals with various compositions and phases were established for various applications, including medical ultrasonic transducers, underwater transducers, acoustic sensors and tweezers. For each device application, recent developments in relaxor-PT ferroelectric crystals were surveyed and compared with state-of-the-art polycrystalline piezoelectrics, with an emphasis on their strong anisotropic features and crystallographic uniqueness, including engineered domain - property relationships. This review starts with an introduction on electroacoustic transducers and the history of piezoelectric materials. The development of the high performance relaxor-PT single crystals, with a focus on their uniqueness in transducer applications, is then discussed. In the third part, various FOMs of piezoelectric materials for a wide range of ultrasound applications, including diagnostic ultrasound, therapeutic ultrasound, underwater acoustic and passive sensors, tactile sensors and acoustic tweezers, are evaluated to provide a thorough understanding of the materials’ behavior under operational conditions. Structure-property-performance relationships are then established. Finally, the impacts and challenges of relaxor

  3. Advantages and Challenges of Relaxor-PbTiO3 Ferroelectric Crystals for Electroacoustic Transducers- A Review.

    PubMed

    Zhang, Shujun; Li, Fei; Jiang, Xiaoning; Kim, Jinwook; Luo, Jun; Geng, Xuecang

    2015-03-01

    Relaxor-PbTiO3 (PT) based ferroelectric crystals with the perovskite structure have been investigated over the last few decades due to their ultrahigh piezoelectric coefficients (d33 > 1500 pC/N) and electromechanical coupling factors (k33 > 90%), far outperforming state-of-the-art ferroelectric polycrystalline Pb(Zr,Ti)O3 ceramics, and are at the forefront of advanced electroacoustic applications. In this review, the performance merits of relaxor-PT crystals in various electroacoustic devices are presented from a piezoelectric material viewpoint. Opportunities come from not only the ultrahigh properties, specifically coupling and piezoelectric coefficients, but through novel vibration modes and crystallographic/domain engineering. Figure of merits (FOMs) of crystals with various compositions and phases were established for various applications, including medical ultrasonic transducers, underwater transducers, acoustic sensors and tweezers. For each device application, recent developments in relaxor-PT ferroelectric crystals were surveyed and compared with state-of-the-art polycrystalline piezoelectrics, with an emphasis on their strong anisotropic features and crystallographic uniqueness, including engineered domain - property relationships. This review starts with an introduction on electroacoustic transducers and the history of piezoelectric materials. The development of the high performance relaxor-PT single crystals, with a focus on their uniqueness in transducer applications, is then discussed. In the third part, various FOMs of piezoelectric materials for a wide range of ultrasound applications, including diagnostic ultrasound, therapeutic ultrasound, underwater acoustic and passive sensors, tactile sensors and acoustic tweezers, are evaluated to provide a thorough understanding of the materials' behavior under operational conditions. Structure-property-performance relationships are then established. Finally, the impacts and challenges of relaxor-PT crystals

  4. Photorefractive effect in ferroelectric liquid crystal blends containing terthiophene photoconductive chiral dopants

    NASA Astrophysics Data System (ADS)

    Sasaki, Takeo; Yoshino, Masanori

    2016-04-01

    Ferroelectric liquid crystalline mixtures composed of a smectic liquid crystal, a photoconductive chiral dopant, and an electron trap reagent exhibit a large photorefractivity with a rapid response. It is expected that the photorefractive FLC blends can be utilized in dynamic amplification of moving optical signals. In the present study, the photorefractive properties of the ferroelectric liquid crystal blends containing different photoconductive chiral dopants were examined. The durability of the photoconductive chiral dopants during laser irradiation was investigated. Tthe effect of the conduction of photogenerated ionic species on the photorefractivity decay was clarified.

  5. Electro-optical investigations of holographic-polymer-dispersed ferroelectric liquid crystals.

    PubMed

    Woltman, Scott J; Eakin, James N; Crawford, Gregory P; Zumer, Slobodan

    2007-12-01

    Uniform alignment of ferroelectric liquid-crystal domains encapsulated by a polymer binder was established through a holographic exposure process. The refractive index modulation in these thin films is modeled as a phase grating that can be electrically addressed to erase the optical diffractive properties. A phenomenological model is developed to take into account a distribution of domain sizes and an effective field that stabilizes the ferroelectric liquid-crystal domains. A diffraction model successfully predicts changes in normalized intensities for first-order diffraction with applied field. These gratings demonstrate microsecond-scale response and relaxation times for various grating pitch sizes between approximately 3 and approximately 12 microm.

  6. Electrically switchable Fresnel lenses in polymer-stabilized ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Yeh, Hui-Chen; Ke, Ming-Wei; Liu, Yu-Mei

    2017-01-01

    In this study, we demonstrate the fabrication of an electrically switchable Fresnel lens based on surface-stabilized ferroelectric liquid crystals (SSFLCs) with polymer networks. The Fresnel lens was fabricated by injecting a monomer-doped ferroelectric liquid crystal into an extremely thin cell and exposing the cell to ultraviolet light through a Fresnel-zone-plate mask. The fabricated Fresnel lens consisted of the SSFLC and polymer-stabilized SSFLC structures. The focusing effect can be switched on by applying an appropriate voltage, and the characteristics of FLCs enable a rapid response on the order of milliseconds.

  7. Single crystal complex oxide on flexible substrate

    NASA Astrophysics Data System (ADS)

    Bakaul, Saidur; Serrao, Claudy; Lee, Oukjae; Salahuddin, Sayeef

    Flexible ferroelectrics are needed for various applications such as biocompatible energy harvesting and flexible memory. In this sector, most of the current research is focused on organic piezoelectric materials which have advantage of flexibility but suffers severely from poor energy conversion and generation efficiency. On the contrary, owing to very high electromechanical coupling factor (representing energy conversion efficiency) complex oxides are the best choices as energy harvesting and transduction elements, especially for transforming mechanical energies into electronic energy. Still their usage in energy harvesting is very limited mainly due to the stringent growth conditions of single crystals, high temperature needed for crystallization and lack of flexibility and stretchability. We have shown that single crystal Pb0.8Zr0.2TiO3 can be epitaxially transferred on flexible plastic substrate. The transferred PZT shows 70 uC/cm2 remnant polarization and dielectric constant over 100 even when it is bent. These results suggest the possibility of single crystal complex oxide devices on flexible platform.

  8. Quantum ferroelectricity in charge-transfer complex crystals

    PubMed Central

    Horiuchi, Sachio; Kobayashi, Kensuke; Kumai, Reiji; Minami, Nao; Kagawa, Fumitaka; Tokura, Yoshinori

    2015-01-01

    Quantum phase transition achieved by fine tuning the continuous phase transition down to zero kelvin is a challenge for solid state science. Critical phenomena distinct from the effects of thermal fluctuations can materialize when the electronic, structural or magnetic long-range order is perturbed by quantum fluctuations between degenerate ground states. Here we have developed chemically pure tetrahalo-p-benzoquinones of n iodine and 4–n bromine substituents (QBr4–nIn, n=0–4) to search for ferroelectric charge-transfer complexes with tetrathiafulvalene (TTF). Among them, TTF–QBr2I2 exhibits a ferroelectric neutral–ionic phase transition, which is continuously controlled over a wide temperature range from near-zero kelvin to room temperature under hydrostatic pressure. Quantum critical behaviour is accompanied by a much larger permittivity than those of other neutral–ionic transition compounds, such as well-known ferroelectric complex of TTF–QCl4 and quantum antiferroelectric of dimethyl–TTF–QBr4. By contrast, TTF–QBr3I complex, another member of this compound family, shows complete suppression of the ferroelectric spin-Peierls-type phase transition. PMID:26076656

  9. Modulation of homochiral Dy(III) complexes: single-molecule magnets with ferroelectric properties.

    PubMed

    Li, Xi-Li; Chen, Chun-Lai; Gao, Yu-Liang; Liu, Cai-Ming; Feng, Xiang-Li; Gui, Yang-Hai; Fang, Shao-Ming

    2012-11-12

    Homochiral Dy(III) complexes: by changing the ligand-to-metal ratio, enantiomeric pairs of a Dy(III) complex of different nuclearity could be obtained. The mono- and dinuclear complexes exhibit characteristics of single-molecule magnets and different slow magnetic relaxation processes. In addition, the dinuclear complexes exhibit ferroelectric behavior, thus representing the first chiral polynuclear lanthanide-based single-molecule magnets with ferroelectric properties.

  10. Polarized micro Raman spectroscopy of multiferroic BiFeO3 single crystals

    NASA Astrophysics Data System (ADS)

    Beekman, C.; Cheong, Sang-Wook; Burch, Kenneth

    2011-03-01

    In Bismuth ferrite (BiFe O3) antiferromagnetic and ferroelectric order parameters coexist at room temperature, making this material an excellent candidate for new functionalities, such as electrical control of ferromagnetism. Despite extensive reports on Raman scattering experiments on single crystals and thin films, controversy still remains in the observation and assignment of the phonon modes. However, proper Raman mode assignment to describe the phonons critical for the multiferroic behavior is necessary. We present polarized micro Raman spectroscopy of single crystals with uniform ferroelectric polarization. Careful examination of the Raman spectra upon crystal rotation enables us to unambiguously assign several (A1 , Ex and Ey) modes.

  11. 10-Gb/s PMD compensation using ferroelectric liquid crystals and several PMD penalty signals

    NASA Astrophysics Data System (ADS)

    Hinz, S.; Sandel, D.; Yoshida-Dierolf, M.; Mirvoda, V.; Noe, Reinhold; Weyrauch, Thomas; Beresnev, L.; Haase, Wolfgang

    1999-04-01

    Polarization mode dispersion (PMD) hampers development of greater than or equal to 10 Gb/s trunk lines but can be compensated by endless polarization controllers and birefringent fiber. We demonstrate automatic 10 Gb/s PMD compensation using three deformed-helix ferroelectric liquid crystal cells.

  12. Lithium niobate single-crystal and photo-functional device

    DOEpatents

    Gopalan, Venkatraman; Mitchell, Terrence E.; Kitamura, Kenji; Furukawa, Yasunori

    2001-01-01

    Provided are lithium niobate single-crystal that requires a low voltage of not larger than 10 kV/nm for its ferroelectric polarization inversion and of which the polarization can be periodically inverted with accuracy even at such a low voltage, and a photo-functional device comprising the crystal. The crystal has a molar fraction of Li.sub.2 O/(Nb.sub.2 O.sub.5 +Li.sub.2 O) of falling between 0.49 and 0.52. The photo-functional device can convert a laser ray being incident thereon.

  13. Multiwall carbon nanotubes doped ferroelectric liquid crystal composites: A study of modified electrical behavior

    NASA Astrophysics Data System (ADS)

    Neeraj; Raina, K. K.

    2014-02-01

    We systematically investigated the role of carbon nanotubes and their nature of interaction with the high polarization ferroelectric liquid crystal molecules that causes a change in the dynamic behavior of the liquid crystals. The carbon nanotubes were functionalized with carboxyl group (-COOH) before dispersion in order to enhance their stability in the liquid crystal medium. For the systematic investigation of a non linear behavior of dispersed composite systems, results for various physical properties were determined by thermal, morphological and dielectric studies in the planer aligned 5 μm thickness cells. An effort has also gone into detail to investigate these properties with varying concentration (0.02 wt%, 0.05 wt% and 0.1 wt%) of multiwall carbon nanotubes. The various carbon nanotubes doped ferroelectric liquid crystal thin film composites have shown enhanced dielectric strength and dielectric permittivity values as compared to the undoped sample.

  14. Longitudinal and transverse pyroelectric effects in a chiral ferroelectric liquid crystal

    SciTech Connect

    Yablonskii, S. V. Bondarchuk, V. V.; Soto-Bustamante, E. A.; Romero-Hasler, P. N.; Ozaki, M.; Yoshino, K.

    2015-04-15

    In this study, we compare the results of experimental investigations of longitudinal and transverse pyroelectric effects in a chiral ferroelectric crystal. In a transverse geometry, we studied freely suspended liquid-crystal films. In both geometries, samples exhibited bistability, demonstrating stable pyroelectric signals of different polarities at zero voltage. It is shown that a bistable cell based on a freely suspended film requires 40 times less energy expenditures as compared to the conventional sandwich-type cell.

  15. Effects of graphene on electro-optic switching and spontaneous polarization of a ferroelectric liquid crystal

    SciTech Connect

    Basu, Rajratan

    2014-09-15

    A small quantity of graphene flakes was doped in a ferroelectric liquid crystal (FLC), and the field-induced ferroelectric electro-optic switching was found to be significantly faster in the FLC + graphene hybrid than that of the pure FLC. Further studies revealed that the suspended graphene flakes enhanced the FLC's spontaneous polarization by improving smectic-C ordering resulting from the π–π electron stacking, and reduced rotation viscosity by trapping some of the free ions of the FLC media. These effects coherently impacted the FLC-switching phenomenon, enabling the FLC molecules to switch faster on reversing an external electric field.

  16. Photovoltaic response around a unique 180° ferroelectric domain wall in single-crystalline BiFe O3

    NASA Astrophysics Data System (ADS)

    Blouzon, C.; Chauleau, J.-Y.; Mougin, A.; Fusil, S.; Viret, M.

    2016-09-01

    Using an experimental setup designed to scan a submicron sized light spot and collect the photogenerated current through larger electrodes, we map the photovoltaic response in ferroelectric BiFe O3 single crystals. We study the effect produced by a unique 180° ferroelectric domain wall (DW) and show that the photocurrent maps are significantly affected by its presence and shape. The effect is large in its vicinity and in the Schottky barriers at the interface with the Au electrodes, but no extra photocurrent is observed when the illuminating spot touches the DW, indicating that this particular entity is not the heart of specific photoelectric properties. Using 3D modeling, we argue that the measured effect is due to the spatial distribution of internal fields which are significantly affected by the charge of the DW due to its distortion.

  17. Large field-induced-strain at high temperature in ternary ferroelectric crystals

    PubMed Central

    Wang, Yaojin; Chen, Lijun; Yuan, Guoliang; Luo, Haosu; Li, Jiefang; Viehland, D.

    2016-01-01

    The new generation of ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ferroelectric single crystals have potential applications in high power devices due to their surperior operational stability relative to the binary system. In this work, a reversible, large electric field induced strain of over 0.9% at room temperature, and in particular over 0.6% above 380 K was obtained. The polarization rotation path and the phase transition sequence of different compositions in these ternary systems have been determined with increasing electric field applied along [001] direction based on x-ray diffraction data. Thereafter, composition dependence of field-temperature phase diagrams were constructed, which provide compositional and thermal prospectus for the electromechanical properties. It was found the structural origin of the large stain, especially at higher temperature is the lattice parameters modulated by dual independent variables in composition of these ternary solid solution crystals. PMID:27734908

  18. Large field-induced-strain at high temperature in ternary ferroelectric crystals

    NASA Astrophysics Data System (ADS)

    Wang, Yaojin; Chen, Lijun; Yuan, Guoliang; Luo, Haosu; Li, Jiefang; Viehland, D.

    2016-10-01

    The new generation of ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ferroelectric single crystals have potential applications in high power devices due to their surperior operational stability relative to the binary system. In this work, a reversible, large electric field induced strain of over 0.9% at room temperature, and in particular over 0.6% above 380 K was obtained. The polarization rotation path and the phase transition sequence of different compositions in these ternary systems have been determined with increasing electric field applied along [001] direction based on x-ray diffraction data. Thereafter, composition dependence of field-temperature phase diagrams were constructed, which provide compositional and thermal prospectus for the electromechanical properties. It was found the structural origin of the large stain, especially at higher temperature is the lattice parameters modulated by dual independent variables in composition of these ternary solid solution crystals.

  19. Dielectric properties of ferroelectric betaine phosphite crystals with a high degree of deuteration

    NASA Astrophysics Data System (ADS)

    Balashova, E. V.; Krichevtsov, B. B.; Yurko, E. I.; Svinarev, F. B.; Pankova, G. A.

    2015-12-01

    The dielectric properties of deuterated betaine phosphite crystals with a high degree of deuteration in the region of the antiferrodistorsive (at T = T c1) and ferroelectric (at T = T c2) phase transitions have been investigated. The temperature behavior of the dielectric permittivity of betaine phosphite and deuterated betaine phosphite has been described within the framework of the Landau thermodynamic model taking into account the biquadratic coupling between the polar order parameter of the ferroelectric transition and the nonpolar order parameter of the antiferrodistorsive phase transition. It has been shown that an increase in the degree of deuteration leads to a decrease in the coupling between the order parameters. An increase in the temperature of the ferroelectric phase transition due to the deuteration of betaine phosphite is caused by an increase in the dielectric permittivity in the symmetric phase above the temperature of the antiferrodistorsive phase transition.

  20. Self-Restoration by Smectic Layer Structures of Monostable Ferroelectric Liquid Crystal in Flexible Devices

    NASA Astrophysics Data System (ADS)

    Fujikake, Hideo; Sato, Hiroto; Isaka, Fumito; Murashige, Takeshi; Kikuchi, Hiroshi; Kurita, Taiichiro; Sato, Fumio

    2004-12-01

    In this paper, we discuss a self-restoration phenomenon affecting smectic layer deformation and molecular alignment in monostable ferroelectric liquid crystals used for flexible displays. First, the mechanical stability of tilted ‘bookshelf’ structures of smectic layers anchored on substrates using alignment layers was examined by precisely shearing two substrates. The microscopic texture of a monostable ferroelectric liquid crystal showed tolerance to shearing and the self-restoration was thought to be due to a smectic layer reconnection phenomenon, whereas a conventional bistable ferroelectric liquid crystal film generated alignment defects due to the tilting of the stable molecular direction. We then fabricated a flexible monostable device containing fine polymer fiber networks, where anchoring of molecularly aligned polymer fibers led to the observation of monostable liquid crystal switching. A uniform liquid crystal alignment was maintained in a 100 mm× 100 mm device even after bending more than 10000 times at a minimum radius of curvature of 20 mm, due to the enhanced shearing tolerance of the smectic layer structure.

  1. Mechanical and thermal transitions in morphotropic PZN-pT and PMN-PT single crystals and their implication for sound projectors.

    PubMed

    Amin, Ahmed; McLaughlin, Elizabeth; Robinson, Harold; Ewart, Lynn

    2007-06-01

    Isothermal compression experiments on multidomain [001] oriented and poled ferroelectric rhombohedral PZN-0.07PT and PMN-0.30PT single crystals revealed elastic instabilities corresponding to zero field ferroelectric-ferroelectric phase transition under mechanical compression. The application of an appropriate dc bias field doubled the stability range of the ferroelectric rhombohedral state under uniaxial compression for both crystals and maintained a linear elastic response. Young's modulus as derived from the quasistatic, zero field stress-strain linear response agreed well with that derived from small signal resonance for the ferroelectric rhombohedral FR state of both PZN-PT and PMN-PT. Elastic compliances s(E)33 as determined from high temperature resonance revealed a monotonically decreasing Young's modulus as a function of temperature in the ferroelectric rhombohedral state with a sudden stiffening near the ferroelectric rhombohedral (FR)-ferroelectric tetragonal (FT) transition. The reversible ferroelectric-ferroelectric transition of morphotropic PZN-PT and PMN-PT single crystals as accessed by mechanical compression is discussed in terms of strain calculations from Devonshire's theory, domain unfolding, and morphotropic phase boundary shift with mechanical stress. The mechanically-induced and thermally-induced ferroelectric-ferroelectric transition trajectories are discussed in terms of the Devonshire theory. Implications of these observations for sound projectors are discussed. A single crystal tonpilz projector fabricated into a 16-element array and a segmented cylinder transducer demonstrated the outstanding capabilities of single crystals to achieve compact, broadband, and high-source level projectors when compared to conventional lead zirconate-titanate PZT8 projectors.

  2. Speckle noise suppression using a helix-free ferroelectric liquid crystal cell

    SciTech Connect

    Andreev, A L; Andreeva, T B; Kompanets, I N; Zalyapin, N V

    2014-12-31

    We have studied the method for suppressing speckle noise in patterns produced by a laser based on a fast-response electro-optical cell with a ferroelectric liquid crystal (FLC) in which helicoid is absent, i.e., compensated for. The character of smectic layer deformation in an electric field is considered along with the mechanism of spatially inhomogeneous phase modulation of a laser beam passing through the cell which is accompanied by the destruction of phase relations in the beam. Advantages of a helix-free FLC cell are pointed out as compared to helical crystal cells studied previously. (liquid crystal devices)

  3. Losses in Ferroelectric Materials.

    PubMed

    Liu, Gang; Zhang, Shujun; Jiang, Wenhua; Cao, Wenwu

    2015-03-01

    Ferroelectric materials are the best dielectric and piezoelectric materials known today. Since the discovery of barium titanate in the 1940s, lead zirconate titanate ceramics in the 1950s and relaxor-PT single crystals (such as lead magnesium niobate-lead titanate and lead zinc niobate-lead titanate) in the 1980s and 1990s, perovskite ferroelectric materials have been the dominating piezoelectric materials for electromechanical devices, and are widely used in sensors, actuators and ultrasonic transducers. Energy losses (or energy dissipation) in ferroelectrics are one of the most critical issues for high power devices, such as therapeutic ultrasonic transducers, large displacement actuators, SONAR projectors, and high frequency medical imaging transducers. The losses of ferroelectric materials have three distinct types, i.e., elastic, piezoelectric and dielectric losses. People have been investigating the mechanisms of these losses and are trying hard to control and minimize them so as to reduce performance degradation in electromechanical devices. There are impressive progresses made in the past several decades on this topic, but some confusions still exist. Therefore, a systematic review to define related concepts and clear up confusions is urgently in need. With this objective in mind, we provide here a comprehensive review on the energy losses in ferroelectrics, including related mechanisms, characterization techniques and collections of published data on many ferroelectric materials to provide a useful resource for interested scientists and engineers to design electromechanical devices and to gain a global perspective on the complex physical phenomena involved. More importantly, based on the analysis of available information, we proposed a general theoretical model to describe the inherent relationships among elastic, dielectric, piezoelectric and mechanical losses. For multi-domain ferroelectric single crystals and ceramics, intrinsic and extrinsic energy

  4. Losses in Ferroelectric Materials

    PubMed Central

    Liu, Gang; Zhang, Shujun; Jiang, Wenhua; Cao, Wenwu

    2015-01-01

    Ferroelectric materials are the best dielectric and piezoelectric materials known today. Since the discovery of barium titanate in the 1940s, lead zirconate titanate ceramics in the 1950s and relaxor-PT single crystals (such as lead magnesium niobate-lead titanate and lead zinc niobate-lead titanate) in the 1980s and 1990s, perovskite ferroelectric materials have been the dominating piezoelectric materials for electromechanical devices, and are widely used in sensors, actuators and ultrasonic transducers. Energy losses (or energy dissipation) in ferroelectrics are one of the most critical issues for high power devices, such as therapeutic ultrasonic transducers, large displacement actuators, SONAR projectors, and high frequency medical imaging transducers. The losses of ferroelectric materials have three distinct types, i.e., elastic, piezoelectric and dielectric losses. People have been investigating the mechanisms of these losses and are trying hard to control and minimize them so as to reduce performance degradation in electromechanical devices. There are impressive progresses made in the past several decades on this topic, but some confusions still exist. Therefore, a systematic review to define related concepts and clear up confusions is urgently in need. With this objective in mind, we provide here a comprehensive review on the energy losses in ferroelectrics, including related mechanisms, characterization techniques and collections of published data on many ferroelectric materials to provide a useful resource for interested scientists and engineers to design electromechanical devices and to gain a global perspective on the complex physical phenomena involved. More importantly, based on the analysis of available information, we proposed a general theoretical model to describe the inherent relationships among elastic, dielectric, piezoelectric and mechanical losses. For multi-domain ferroelectric single crystals and ceramics, intrinsic and extrinsic energy

  5. Influence of isopropanol on ferroelectric properties of triglycine sulfate crystals

    NASA Astrophysics Data System (ADS)

    Milovidova, S. D.; Rogazinskaya, O. V.; Sidorkin, A. S.; Nguen, Kh. T.; Bykova, A. V.

    2015-03-01

    The dielectric and switching properties of triglycine sulfate (TGS) crystals grown from aqua solution with isopropanol have been studied. It has been shown that their behavior has common features with the behavior of the TGS crystals irradiated by X-rays, and also with the TGS crystals doped with L, α-alanine.

  6. Ultrafast Photoinduced Electric-Polarization Switching in a Hydrogen-Bonded Ferroelectric Crystal

    NASA Astrophysics Data System (ADS)

    Iwano, K.; Shimoi, Y.; Miyamoto, T.; Hata, D.; Sotome, M.; Kida, N.; Horiuchi, S.; Okamoto, H.

    2017-03-01

    Croconic acid crystals show proton displacive-type ferroelectricity with a large spontaneous polarization reaching 20 μ C /cm2 , which originates from the strong coupling of proton and π -electron degrees of freedom. Such a coupling makes us expect a large polarization change by photoirradiations. Optical-pump second-harmonic-generation-probe experiments reveal that a photoexcited croconic-acid crystal loses the ferroelectricity substantially with a maximum quantum efficiency of more than 30 molecules per one absorbed photon. Based on density functional calculations, we theoretically discuss possible pathways toward the formation of a one-dimensional domain with polarization inversion and its recovery process to the ground state by referring to the dynamics of experimentally obtained polarization changes.

  7. Origin of weak ferroelectricity in semiconductive Sb2S3 crystal

    NASA Astrophysics Data System (ADS)

    Žigas, Leonardas; Audzijonis, Algirdas; Grigas, Jonas

    2017-02-01

    The paper presents the results of the investigations of electronic potential dependencies upon the normal co-ordinates of B1u mode in a large temperature range for the Sb2S3 crystal. The results revealed high anharmonicity of Sb and S atoms in this highly covalent semiconductive compound and B1u - mode polar distortion with temperature leading to appearance of weak ferroelectricity.

  8. Ferroelectric-like response from the surface of SrTiO₃ crystals at high temperatures

    SciTech Connect

    Jyotsna, Shubhra; Arora, Ashima; Sekhon, Jagmeet S.; Sheet, Goutam

    2014-09-14

    Since SrTiO₃ has a high dielectric constant, it is used as a substrate for a large number of complex physical systems for electrical characterization. Since SrTiO₃ crystals are known to be non-ferroelectric/non-piezoelectric at room temperature and above, SrTiO₃ has been believed to be a good choice as a substrate/base material for PFM (Piezoresponse Force Microscopy) on novel systems at room temperature. In this paper, from PFM-like measurement using an atomic force microscope on bare crystals of (110) SrTiO₃ we show that ferroelectric and piezoelectric-like response may originate from bare SrTiO₃ at remarkably high temperatures up to 420 K. Electrical domain writing and erasing are also possible using a scanning probe tip on the surface of SrTiO₃ crystals. This observation indicates that the role of the electrical response of SrTiO₃ needs to be revisited in the systems where signature of ferroelectricity/piezoelectricity has been previously observed with SrTiO₃ as a substrate/base material.

  9. Room-temperature Ferroelectricity in Uniaxially Strained Single-crystalline SrTiO3 Freestanding Films

    NASA Astrophysics Data System (ADS)

    Lu, Di; Crossley, Sam; Yoon, Hyeok; Hikita, Yasuyuki; Hwang, Harold

    Single crystal pure bulk SrTiO3 (STO) is an incipient ferroelectric whose dielectric permittivity rises to high values as temperature is reduced, but remains paraelectric to the lowest observable temperatures. Ferroelectric phases of STO may be stabilized via doping and strain, whose common effect is to split the spatial free energy well of ionic displacements. With epitaxial strain of the order of a few percent, Curie temperatures TC ~293 K have been observed. By exploiting a highly novel process to exfoliate epitaxial oxide films deposited by pulsed laser deposition, we have isolated sub-100 nm-thick freestanding films of STO which are readily manipulated and mechanically strained to high levels. Measurements of the in-plane dielectric properties for various applied strains reveal a continuously tunable ferroelectric TC. A two-order-of-magnitude enhanced dielectric response is displayed by a 1.2%-strained sample at TC ~290 K, as compared with the same sample unstrained at the same temperature. This is consistent with a phenomenological Ginzburg-Landau model, and previous studies on anchored films. The functional properties of strained STO have generated intense interest and debate, and have been suggested for device applications due to e.g. high voltage-tunable dielectric properties. Our work exhibits strain as a continuously variable experimental degree of freedom, which can induce numerous functional effects.

  10. Photonic band gap structure for a ferroelectric photonic crystal at microwave frequencies.

    PubMed

    King, Tzu-Chyang; Chen, De-Xin; Lin, Wei-Cheng; Wu, Chien-Jang

    2015-10-10

    In this work, the photonic band gap (PBG) structure in a one-dimensional ferroelectric photonic crystal (PC) is theoretically investigated. We consider a PC, air/(AB)N/air, in which layer A is a dielectric of MgO and layer B is taken to be a ferroelectric of Ba0.55Sr0.45TiO3 (BSTO). With an extremely high value in the dielectric constant in BSTO, the calculated photonic band structure at microwave frequencies exhibits some interesting features that are significantly different from those in a usual dielectric-dielectric PC. First, the photonic transmission band consists of multiple and nearly discrete transmission peaks. Second, the calculated bandwidth of the PBG is nearly unchanged as the angle of incidence varies in the TE wave. The bandwidth will slightly reduce for the TM mode. Thus, a wide omnidirectional PBG can be obtained. Additionally, the effect of the thickness of the ferroelectric layer on the PBG is much more pronounced compared to the dielectric layer thickness. That is, the increase of ferroelectric thickness can significantly decrease the PBG bandwidth.

  11. Polymer-stabilized ferroelectric liquid crystal for flexible displays using plastic substrates

    NASA Astrophysics Data System (ADS)

    Fujikake, Hideo; Murashige, Takeshi; Sato, Hiroto; Iino, Yoshiki; Kikuchi, Hiroshi; Kawakita, Masahiro; Tsuchiya, Yuzuru

    2001-12-01

    We have developed a ferroelectric liquid crystal device with a novel structure containing a polymer fiber network for flexible lightweight displays using thin plastic substrates. The aligned polymer fibers of sub-micrometers -diameter were formed under ultraviolet light irradiation in a heated nematic- phase solution consisting of liquid crystal and monofunctional acrylate monomer. The rigid polymer network was found to adhere to the two plastic substrates, and the uniform liquid crystal alignment provided a contrast ratio of 100:1 for a monomer concentration of 20 wt%. This device achieves a continuous grayscale capability as a result of change in the spatial distribution of small liquid crystal domains, and also exhibits a fast response time of 80 microsecond(s) due to high-purity separation of polymer and liquid crystal materials. It therefore has attractive features for flexible moving-image display applications.

  12. Ferroelectric Liquid Crystals in Microcapillaries: Observation of Different Electro-optic Switching Mechanisms.

    PubMed

    Knust, Steffen; Wahle, Markus; Kitzerow, Heinz-S

    2017-04-13

    Ferroelectric liquid crystals (FLCs) can provide fast electro-optic switching effects in photonic crystal fibers, which are promising for developing integrated optical modulators to be used for optical telecommunication. The present study describes experiments on capillaries filled with FLCs, which pave the way toward application of FLCs in state-of-the-art solid core microstructured optical fibers. A method to achieve uniform alignment of the helix axis and the appearance of two different switching modes with switching times in the submillisecond range are found. An additional slow relaxation that was reported recently can be attributed to space charge fields, which may appear due to the migration of ions.

  13. Polarization Raman Spectral Microscopy of Polymer Fibers Formed in Ferroelectric Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Fujikake, Hideo; Murashige, Takeshi; Sato, Hiroto; Kawakita, Masahiro; Kikuchi, Hiroshi

    2003-01-01

    This letter focuses on Raman spectral microscopy of polymer fiber networks, which are formed by the photopolymerization of liquid crystalline acrylate monomers in low-molecular-weight ferroelectric liquid crystal, using polarized infrared light to excite the polymer molecules. It was found that the tolane side-chain molecules of the polymer are significantly orientated with the liquid crystal alignment along the rubbing direction of the polyimide alignment layers that are coated on the substrates. A model is proposed for the formation of the polymer based on the alignment evaluation results.

  14. Thermal Shock Tolerance of Ferroelectric Liquid Crystal Stabilized by Aligned Polymer Fibers

    NASA Astrophysics Data System (ADS)

    Fujikake, Hideo; Murashige, Takeshi; Sato, Hiroto; Fujisaki, Yoshihide; Kawakita, Masahiro; Kikuchi, Hiroshi; Kurita, Taiichiro

    2003-02-01

    In this paper, we report the marked enhancement of thermal shock tolerance of smectic layer structures of ferroelectric liquid crystal stabilized by aligned fine polymer fibers, which were formed by photopolymerization-induced phase separation. It was found that a smectic layer structure with such polymer fibers, which are aligned perpendicular to the smectic layer, generates no zigzag defects even after the composite film is cooled to -15°C, which is lower than the chiral smectic C-to-crystal phase-transition temperature, or heated to 100°C, which is above the chiral nematic-to-isotropic phase-transition temperature.

  15. Creep of Oxide Single Crystals

    DTIC Science & Technology

    1990-08-01

    literature data on Gd 3Ga5O1 2 (8) indicate that garnets may be highly deformation resistant at temperatures very close to their melting points...Data for Yttrium Aluminum Garnet Single Crystals Temperature Stress Creep Rate (sec 1 ) for Given Stress Direction (0C) (MPa) [111] [110] [100] 1650...Gadolinium Gallium Garnet Single Crystals," J.Mat.Sci., 17, 878-884 (1982). 9. B.M. Wanklyn, Clarendon Laboratory, personal communicaticn. 10. S.B. Austerman

  16. Research on Crystal and Film Ferroelectric Materials for Optoelectronic Applications.

    DTIC Science & Technology

    1988-03-01

    Experimental determination of the millimeter wave dielectric and dn/dE values for La- doped SBN:60 at room and cryogenic temperatures for various crystal...fact, been directed toward higher permittivity. PBN doped with La3+ was prepared as grain-oriented ceramics, small crystals of SCNN were grown by the...Czochralski technique, and new BSKNN compo- sitions were prepared by sintering. In addition, we found that La doping of SBN:60 or :75 dramatically

  17. Boundary layer elasto-optic switching in ferroelectric liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.

    1992-01-01

    The first experimental observation of a change in the director azimuthal angle due to applied shear stress is reported in a sample configuration involving a liquid-crystal-coated top surface exposed directly to gas flow. The electrooptic response caused by the shear stress is large, fast, and reversible. These findings are relevant to the use of liquid crystals in boundary layer investigations on wind tunnel models.

  18. Electromechanical properties of high coupling single crystals under large electric drive and uniaxial compression.

    PubMed

    Amin, Ahmed

    2005-10-01

    This work investigates the 33-mode electromechanical response of relaxor-ferroelectric lead magnesium niobate-lead titanate (PMN-PT) single crystals when driven with large fields approximately 0.4 MV/m under a combined direct current (DC) field and mechanical bias similar to those used in the design of sound projectors. It demonstrates that the remarkable small signal length extensional coupling (k33 > 0.90) and other electromechanical properties of morphotropic PMN-PT single crystals prevail under large drive. The observed k33 roll-off at 42 MPa compressive stress is analyzed in terms of the recent structural data and the high-order Devonshire theory of possible ferroelectric-ferroelectric transition trajectories.

  19. Optical correlator using very-large-scale integrated circuit/ferroelectric-liquid-crystal electrically addressed spatial light modulators

    NASA Technical Reports Server (NTRS)

    Turner, Richard M.; Jared, David A.; Sharp, Gary D.; Johnson, Kristina M.

    1993-01-01

    The use of 2-kHz 64 x 64 very-large-scale integrated circuit/ferroelectric-liquid-crystal electrically addressed spatial light modulators as the input and filter planes of a VanderLugt-type optical correlator is discussed. Liquid-crystal layer thickness variations that are present in the devices are analyzed, and the effects on correlator performance are investigated through computer simulations. Experimental results from the very-large-scale-integrated / ferroelectric-liquid-crystal optical-correlator system are presented and are consistent with the level of performance predicted by the simulations.

  20. Single-step colloidal processing of stable aqueous dispersions of ferroelectric nanoparticles for biomedical imaging

    NASA Astrophysics Data System (ADS)

    Zribi, Olena; Garbovskiy, Yuriy; Glushchenko, Anatoliy

    2014-12-01

    The biomedical applications of ferroelectric nanoparticles rely on the production of stable aqueous colloids. We report an implementation of the high energy ball milling method to produce and disperse ultrafine BaTiO3 nanoparticles in an aqueous media in a single step. This technique is low-cost, environmentally friendly and has the capability to control nanoparticle size and functionality with milling parameters. As a result, ultrafine nanoparticles with sizes as small as 6 nm can be produced. These nanoparticles maintain ferroelectricity and can be used as second harmonic generating nanoprobes for biomedical imaging. This technique can be generalized to produce aqueous nanoparticle colloids of other imaging materials.

  1. Development of Ferroelectric Liquid Crystals with Enhanced Nonlinear Optical Properties.

    DTIC Science & Technology

    1994-04-24

    cyclic cores known to produce the smectic C* phase are benzene, cyclohexane, pyridine , and pyrimidine. The tails could be n -alkyl chains containing...one or more chiral centers. Locally, the molecules self-organize into smetic liquid crystal layers with the director n tilted with respect to the...manifested through a spontaneous polarization P. defined by: P = (z x n )P. The spontaneous polarization magnitude is a function of the chiral center in

  2. Electrical Freedericksz transitions in nematic liquid crystals containing ferroelectric nanoparticles

    NASA Astrophysics Data System (ADS)

    Cîrtoaje, Cristina; Petrescu, Emil; Stoian, Victor

    2015-03-01

    A new theoretical approach was elaborated to explain the contradictions reported in many papers about the electric threshold for Freedericksz transition in nematic liquid crystal (NLC) with ferroparticles additives. The free energy density of the mixture was estimated and the contributions of the interaction energy of NLC molecules with ferroparticles surface were calculated. Experimental results for 5CB-BaTiO3 mixture are given.

  3. Development of single crystal membranes

    NASA Technical Reports Server (NTRS)

    Stormont, R. W.; Cocks, F. H.

    1972-01-01

    The design and construction of a high pressure crystal growth chamber was accomplished which would allow the growth of crystals under inert gas pressures of 2 MN/sq m (300 psi). A novel crystal growth technique called EFG was used to grow tubes and rods of the hollandite compounds, BaMgTi7O16, K2MgTi7O16, and tubes of sodium beta-alumina, sodium magnesium-alumina, and potassium beta-alumina. Rods and tubes grown are characterized using metallographic and X-ray diffraction techniques. The hollandite compounds are found to be two or three-phase, composed of coarse grained orientated crystallites. Single crystal c-axis tubes of sodium beta-alumina were grown from melts containing excess sodium oxide. Additional experiments demonstrated that crystals of magnesia doped beta-alumina and potassium beta-alumina also can be achieved by this EFG technique.

  4. Microscopic three-dimensional topometry with ferroelectric liquid-crystal-on-silicon displays.

    PubMed

    Proll, Klaus-Peter; Nivet, Jean-Marc; Körner, Klaus; Tiziani, Hans J

    2003-04-01

    When three dimensional measurements are conducted with fringe projection, the quality of the grating used for the generation of the fringes is important. It has a direct influence on the achievable depth resolution in a given measurement setup. In the past, Ronchi grating or gratings written in nematic liquid-crystal displays or in digital micromirror devices have been used. We report on the application of a reflective ferroelectric liquid-crystal-on-silicon display as the fringe-generating element in a setup based on a stereo microscope. With this device the depth resolution of measurements by use of phase-shifting algorithms can be significantly improved compared with the application of a Ronchi grating or a nematic liquid-crystal display.

  5. Single Crystal Surfaces

    NASA Astrophysics Data System (ADS)

    Aguilar-Santillan, Joaquin

    2014-06-01

    The present work studies (0001) Al2O3 and (111) Al2MgO4 wetting with pure molten Al by the sessile drop technique from 1073 K to 1473 K (800 °C to 1200 °C) under Ar at PO2 10-15 Pa. Al pure liquid wets a smooth and chemically homogeneous surface of an inert solid, the wetting driving force ( t, T) can be readily studied when surface solid roughness increases in the system. Both crystals planes (0001) Al2O3 and (111) Al2MgO4 have crystallographic surfaces with identical O-2 crystalline positions however considering Mg2+ content in Al2MgO4 structure may influence a reactive mode. Kinetic models results under similar experimental conditions show that Al wetting on (0001) Al2O3 is less reactive than (111) Al2MgO4, however at >1273 K (1000 °C) (0001) Al2O3 transformation occurs and a transition of wetting improves. The (111) Al2MgO4 and Al system promotes interface formations that slow its wetting process.

  6. Effects of ferroelectric nanoparticles on ion transport in a liquid crystal

    NASA Astrophysics Data System (ADS)

    Basu, Rajratan; Garvey, Alfred

    2014-10-01

    A small quantity of BaTiO3 ferroelectric nanoparticles (FNPs) of 50 nm diameter was doped in a nematic liquid crystal (LC), and the free ion concentration was found to be significantly reduced in the LC + FNP hybrid compared to that of the pure LC. The strong electric fields, due to the permanent dipole moment of the FNPs, trapped some mobile ions, reducing the free ion concentration in the LC media. The reduction of free ions was found to have coherent impacts on the LC's conductivity, rotational viscosity, and electric field-induced nematic switching.

  7. Effects of ferroelectric nanoparticles on ion-transport in a liquid crystal

    NASA Astrophysics Data System (ADS)

    Garvey, Alfred; Basu, Rajratan

    2015-03-01

    A small quantity of BaTiO3 ferroelectric nanoparticles (FNPs) of 50 nm diameter was doped in a nematic liquid crystal (LC), and the free ion concentration was found to be significantly reduced in the LC +FNP hybrid compared to that of the pure LC. The strong electric fields, due to the permanent dipole moment of the FNPs, trapped some mobile ions, reducing the free ion concentration in the LC media. The reduction of free ions was found to have coherent impacts on the LC's conductivity, rotational viscosity, and electric field-induced nematic switching.

  8. Fast switchable grating based on orthogonal photo alignments of ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Srivastava, A. K.; Hu, Wei; Chigrinov, V. G.; Kiselev, A. D.; Lu, Yan-Qing

    2012-07-01

    We demonstrate a fast switchable grating based on ferroelectric liquid crystals and orthogonal planar alignment by means of photo alignments. Both 1D and 2D gratings have been constructed. The proposed diffracting element provides fast response time of around 20 μs, contrast of 7000:1 and high diffraction efficiency, at the electric field of 6 V/μm. The saturated electro-optical (EO) states up to very high frequency (≈5 kHz) are the real advantage of the proposed switchable grating, which opens several opportunities to improve the quality of existing devices and to find new applications.

  9. Supramolecular ferroelectrics

    NASA Astrophysics Data System (ADS)

    Tayi, Alok S.; Kaeser, Adrien; Matsumoto, Michio; Aida, Takuzo; Stupp, Samuel I.

    2015-04-01

    Supramolecular chemistry uses non-covalent interactions to coax molecules into forming ordered assemblies. The construction of ordered materials with these reversible bonds has led to dramatic innovations in organic electronics, polymer science and biomaterials. Here, we review how supramolecular strategies can advance the burgeoning field of organic ferroelectricity. Ferroelectrics -- materials with a spontaneous and electrically reversible polarization -- are touted for use in non-volatile computer memories, sensors and optics. Historically, this physical phenomenon has been studied in inorganic materials, although some organic examples are known and strong interest exists to extend the search for ferroelectric molecular systems. Other undiscovered applications outside this regime could also emerge. We describe the key features necessary for molecular and supramolecular dipoles in organic ferroelectrics and their incorporation into ordered systems, such as porous frameworks and liquid crystals. The goal of this Review is to motivate the development of innovative supramolecular ferroelectrics that exceed the performance and usefulness of known systems.

  10. Calculation of the efficiency of polarization-insensitive surface-stabilized ferroelectric liquid-crystal diffraction gratings.

    PubMed

    Brown, Carl V; Kriezis, Emmanouil E

    2003-05-01

    A rigorous analysis is presented of the diffraction efficiency of a polarization-insensitive surface-stabilized ferroelectric liquid-crystal (SSFLC) phase grating, taking full account of the internal structure of the ferroelectric liquid-crystal layer. When no field is applied, the twisted director profile in the relaxed state gives an optimum diffraction efficiency for a device thickness between the half-wave-plate and the full-wave-plate conditions. The influence of the magnitude of the spontaneous polarization and applied ac fields are investigated, and it is shown that the diffraction efficiency of a binary SSFLC phase grating can be strongly enhanced with the technique of ac stabilization.

  11. Pressure dependence of the electro-optic response function in partially exposed polymer dispersed ferroelectric liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Holmes, H. K.

    1993-01-01

    Ferroelectric liquid crystals in a new configuration, termed partially exposed polymer dispersed ferroelectric liquid crystal (PEPDFLC), respond to external pressures and demonstrate pressure-induced electro-optic switching response. When the PEPDFLC thin film is sandwiched between two transparent conducting electrodes, one a glass plate and the other a flexible sheet such as polyvenylidene fluoride, the switching characteristics of the thin film are a function of the pressure applied to the flexible transparent electrode and the bias voltage across the electrodes. Response time measurements reveal a linear dependence of the change in electric field with external pressure.

  12. Crystal ball single event display

    SciTech Connect

    Grosnick, D.; Gibson, A.; Allgower, C.; Alyea, J. |

    1997-10-15

    The Single Event Display (SED) is a routine that is designed to provide information graphically about a triggered event within the Crystal Ball. The SED is written entirely in FORTRAN and uses the CERN-based HICZ graphing package. The primary display shows the amount of energy deposited in each of the NaI crystals on a Mercator-like projection of the crystals. Ten different shades and colors correspond to varying amounts of energy deposited within a crystal. Information about energy clusters is displayed on the crystal map by outlining in red the thirteen (or twelve) crystals contained within a cluster and assigning each cluster a number. Additional information about energy clusters is provided in a series of boxes containing useful data about the energy distribution among the crystals within the cluster. Other information shown on the event display include the event trigger type and data about {pi}{sup o}`s and {eta}`s formed from pairs of clusters as found by the analyzer. A description of the major features is given, along with some information on how to install the SED into the analyzer.

  13. Light modulation in planar aligned short-pitch deformed-helix ferroelectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Kotova, Svetlana P.; Samagin, Sergey A.; Pozhidaev, Evgeny P.; Kiselev, Alexei D.

    2015-12-01

    We study both experimentally and theoretically modulation of light in a planar aligned deformed-helix ferroelectric liquid crystal (DHFLC) cell with subwavelength helix pitch, which is also known as a short-pitch DHFLC. In our experiments, the azimuthal angle of the in-plane optical axis and electrically controlled parts of the principal in-plane refractive indices are measured as a function of voltage applied across the cell. Theoretical results giving the effective optical tensor of a short-pitch DHFLC expressed in terms of the smectic tilt angle and the refractive indices of the ferroelectric liquid crystal (FLC) are used to fit the experimental data. The optical anisotropy of the FLC material is found to be weakly biaxial. For both the transmissive and reflective modes, the results of fitting are applied to model the phase and amplitude modulation of light in the DHFLC cell. We demonstrate that if the thickness of the DHFLC layer is about 50 μ m , the detrimental effect of field-induced rotation of the in-plane optical axes on the characteristics of an axicon designed using the DHFLC spatial light modulator in the reflective mode is negligible.

  14. Observation of adsorption behavior of biomolecules on ferroelectric crystal surfaces with polarization domain patterns

    NASA Astrophysics Data System (ADS)

    Nakayama, Tomoaki; Isobe, Akiko; Ogino, Toshio

    2016-08-01

    Lithium tantalate (LiTaO3) is one of the ferroelectric crystals that exhibit spontaneous polarization domain patterns on its surface. We observed the polarization-dependent adsorption of avidin molecules, which are positively charged in a buffer solution at pH 7.0, on LiTaO3 surfaces caused by electrostatic interaction at an electrostatic double layer using atomic force microscopy (AFM). Avidin adsorption in the buffer solution was confirmed by scratching the substrate surfaces using the AFM cantilever, and the adsorption patterns were found to depend on the avidin concentration. When KCl was added to the buffer solution to weaken the electrostatic double layer interaction between avidin molecules and LiTaO3 surfaces, adsorption domain patterns disappeared. From the comparison between the adsorption and chemically etched domain patterns, it was found that avidin molecule adsorption is enhanced on negatively polarized domains, indicating that surface polarization should be taken into account in observing biomolecule behaviors on ferroelectric crystals.

  15. Stacking fault energy in some single crystals

    NASA Astrophysics Data System (ADS)

    Vora, Aditya M.

    2012-06-01

    The stacking fault energy of single crystals has been reported using the peak shift method. Presently studied all single crystals are grown by using a direct vapor transport (DVT) technique in the laboratory. The structural characterizations of these crystals are made by XRD. Considerable variations are shown in deformation (α) and growth (β) probabilities in single crystals due to off-stoichiometry, which possesses the stacking fault in the single crystal.

  16. Relaxor-PT Single crystals: Observations and Developments

    PubMed Central

    Zhang, Shujun; Shrout, Thomas R.

    2011-01-01

    Relaxor-PT based ferroelectric single crystals Pb(Zn1/3Nb2/3)O3–PbTiO3 (PZNT) and Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMNT) attracted lot of attentions in last decade due to their ultra high electromechanical coupling factors and piezoelectric coefficients. However, owing to a strongly curved morphotropic phase boundary (MPB), the usage temperature of these perovskite single crystals is limited by TRT - the rhombohedral to tetragonal phase transition temperature, which occurs at significantly lower temperatures than the Curie temperature TC. Furthermore, the low mechanical quality factors and coercive fields of these crystals, usually being on the order of ~70 and 2–3kV/cm, respectively, restrict their usage in high power applications. Thus, it is desirable to have high performance crystals with high temperature usage range and high power characteristics. In this survey, different binary and ternary crystal systems were explored, with respect to their temperature usage range, general trends of dielectric and piezoelectric properties of relaxor-PT crystal systems were discussed related to their TC/TRT. In addition, two approaches were proposed to improve mechanical Q values, including acceptor dopant strategy, analogous to “hard” polycrystalline ceramics, and anisotropic domain engineering configurations. PMID:20889397

  17. Synthesis and Characterization of Novel Ferromagnetic, Ferroelectric, Single Phase and Composite Multiferroic Mesoporous Materials

    NASA Astrophysics Data System (ADS)

    Quickel, Thomas Eugene

    Mesoporous nanostructures offer facile routes to novel materials with interesting and often unparalleled properties. Ferrimagnetic, ferroelectric and multiferroic phases, the latter comprising materials that simultaneously possess multiple order parameters, are of great technological importance. Developments in our knowledge of and ability to produce new materials exploiting their properties could have fundamental impacts. Employing versatile solution phase chemistry techniques utilizing co-assembly between organic block co-polymers and inorganic metal precursors, we are able to produce 3-dimensional porous nano-structures in thin film format. Mesoporous frameworks comprising various magnetic ferrites are explored in chapters 2, 3 & 4. The crystal structure and nanoscale architecture for each material is thoroughly examined, and the effects of mesoporosity on the magnetic characteristics of the individual ferrites are determined. The ferrites investigated (MFe2O4,M=Co, Zn, Ni, Mg) are magnetostrictive as their magnet moments are subject to change upon straining of the crystal lattice. It was observed that the nano-scale architecture imparts novel strain states on to the polycrystalline phases and spin re-orientation of their magnetic moment results, emulating results that, previous to the finding in this study, were exclusive to epitaxial growth techniques. Furthermore, the presence of high surface area, resulting from mesoporosity, increases surface spin states drastically altering the magnetic functionality of porous ferrites versus their bulk counterparts. The effects of mesoporosity on piezoelectric materials was also investigated. Piezoelectrics comprise a fascinating class of materials that exhibit internal creation of charge upon the action of mechanical strain, the reverse of which is also true. Mesoporous piezoelectric phases were successfully prepared, and the effects of porosity on the ferroelectric order paramter were established. The presence of pores

  18. Electrostrain enhancement at an invisible boundary in a single ferroelectric phase

    NASA Astrophysics Data System (ADS)

    Zhao, Luo; Ke, Xiaoqin; Wang, Weichen; Zhang, Le; Zhou, Chao; Zhou, Zhijian; Zhang, Lixue; Ren, Xiaobing

    2017-01-01

    In ferroelectric materials the maximum electrostrain effect usually occurs at a phase boundary (often referred to as a "morphotropic phase boundary") between two or more different phases due to lattice instability at such compositions. As a result it is not expected that the electrostrain maximum can appear in a single ferroelectric phase regime which is away from lattice instability. In this Rapid Communication we report an unexpected finding that the electrostrain maximum occurs in a single rhombohedral phase region of the (1 -x %) Ba (T i0.8H f0.2 ) O3-x %(B a0.7C a0.3 ) Ti O3 system. The composition showing the maximum electrostrain corresponds to an "invisible boundary" within the single ferroelectric phase, which is a vertical line starting from the quadruple point of the system. At the invisible boundary other anomalies, such as maximum spontaneous polarization also appear. The origin of electrostrain enhancement at the invisible boundary is considered to correlate with an easy polarization extension inherited from the quadruple point. The electrostrain enhancement effect at the invisible boundary has the advantage of having better temperature stability as compared with that at a phase boundary and thus may provide a way for designing high-electrostrain materials with improved temperature stability.

  19. Fundamental display properties of flexible devices containing polymer-stabilized ferroelectric liquid crystal between plastic substrates

    NASA Astrophysics Data System (ADS)

    Fujikake, Hideo; Murashige, Takeshi; Sato, Hiroto; Iino, Yoshiki; Kawakita, Masahiro; Kikuchi, Hiroshi

    2002-09-01

    We describe several fundamental display properties of a flexible ferroelectric liquid crystal device containing polymer fibers between thin plastic substrates. The composite film of liquid crystal and polymer was created from a solution of liquid crystal and monomer materials between the plastic substrates under ultraviolet light irradiation. The dynamic electrooptic response to analog voltage pulses was examined with an incidence of laser beam light, and its light modulation property exhibited good linearity in continuous gray-scale capability. The excellent spatial uniformity of liquid crystal alignment formed between the flexible substrates resulted in high-contrast light modulation, although slight spontaneous bending of liquid crystal alignment in the device plane was recognized. When the laser light beam was obliquely incident on the flexible display device, the measured transmittance revealed that the device has a wide viewing angle of more than 100 deg without contrast reversal. This is considered to be caused by the molecular switching in the device plane and the thin electrooptic layer in the display device.

  20. Ferroelectric properties of vinylidene fluoride/tetrafluoroethylene copolymer thin films consisting of needle-like crystals

    NASA Astrophysics Data System (ADS)

    Nakagawa, Yuuta; Hashizume, Yoichiro; Nakajima, Takashi; Okamura, Soichiro

    2016-05-01

    Unique ferroelectric vinylidene fluoride (VDF)/tetrafluoroethylene (TeFE) copolymer thin films consisting of needle-like crystals were formed using Au-sputtered substrates. The VDF/TeFE films with a mixing ratio of 80:20 mol % were melted at 170 °C for 30 min and then recrystallized at 116 °C for 300 min. The molecules in the resultant needle-like crystals had a β-phase form and showed 200/110 orientation, while the direction of each needle-like crystal was random in-plane. The remanent polarization of the 450-nm-thick VDF/TeFE films consisting of the needle-like crystals were estimated to be 62 mC/m2 from the electric displacement vs electric field (D-E) hysteresis measurement at the applied field of 156 MV/m and the frequency of 10 Hz. The remanent polarization of 62 mC/m2 was approximately 50% larger than that of conventional VDF/TeFE films consisting of plate-like crystals.

  1. Observation of Structural Phase Transition in Ferroelectric Crystals Using Green Fluorescence Protein

    NASA Astrophysics Data System (ADS)

    Sedarous, Salah; Wessels, William

    1998-03-01

    The Green Fluorescence Protein (GFP) of the jellyfish Aequorea Victoria has attracted widespread interest as a biomolecular marker. It has created many applications in a variety of systems ranging from cell biology to biomedicine. One important application of GFP fluorescence is the detection of structural transitions in biomolecules.In order to examine the sensitivity of the protein fluorescence to structural changes, we sequestered GFP in ferroelectric crystals such as Triglycine sulfate (TGS) and Rochelle salt (RS). TGS has a second order phase transition at 49 C while RS has two phase transitions at -18 and +24 C. The peak of the fluorescence spectrum changes from 510 nm in solution to 470 nm in the crystal indicating a shift of the two absorption bands in the protein upon crystallization. The fluorescence intensity of GFP in TGS decreases as the temperature of the crystal approaches T_C, while its spectrum in RS shows complex changes with temperature. The changes in the time-resolved data are similar to that of the steady state data. Our data show that the onset of structural phase transition in these crystals is clearly detectable from the spectral changes of this chromophore. Other applications of this protein in time-resolved solid state dynamics will be discussed.

  2. Adaptive beam steering implemented in a ferroelectric liquid-crystal spatial-light-modulator free-space, fiber-optic switch.

    PubMed

    Johansson, Mathias; Hård, Sverker; Robertson, Brian; Manolis, Ilias; Wilkinson, Timothy; Crossland, William

    2002-08-10

    Active alignment of a 1 x 8 free-space optical switch was studied experimentally. Optical signals, carried on single-mode fibers, were switched by a ferroelectric liquid-crystal-on-silicon spatial light modulator. Continuous measurement of the in-coupled power to the fibers provided feedback for the switch control. The switch automatically located and locked to the output fibers. An advantage with adaptive switches of a similar kind is relaxed geometrical tolerances in the switch assembly. Further, such switches can adapt to possible geometrical changes and light wavelength drift during operation.

  3. GALLIUM ARSENIDE DENDRITE SINGLE CRYSTAL PROGRAM

    DTIC Science & Technology

    ARSENIDES, *GALLIUM COMPOUNDS, *LABORATORY FURNACES, * SOLAR CELLS , CRUCIBLES, DESIGN, DIFFUSION, EXPLOSIONS, INTERMETALLIC COMPOUNDS, MATERIALS, PHOSPHORUS, SINGLE CRYSTALS, TEMPERATURE CONTROL, ZINC

  4. Pyroelectric field assisted ion migration induced by ultraviolet laser irradiation and its impact on ferroelectric domain inversion in lithium niobate crystals

    SciTech Connect

    Ying, C. Y. J.; Mailis, S.; Daniell, G. J.; Steigerwald, H.; Soergel, E.

    2013-08-28

    The impact of UV laser irradiation on the distribution of lithium ions in ferroelectric lithium niobate single crystals has been numerically modelled. Strongly absorbed UV radiation at wavelengths of 244–305 nm produces steep temperature gradients which cause lithium ions to migrate and result in a local variation of the lithium concentration. In addition to the diffusion, here the pyroelectric effect is also taken into account which predicts a complex distribution of lithium concentration along the c-axis of the crystal: two separated lithium deficient regions on the surface and in depth. The modelling on the local lithium concentration and the subsequent variation of the coercive field are used to explain experimental results on the domain inversion of such UV treated lithium niobate crystals.

  5. SrxBa1-xNb2O6-δ Ferroelectric-thermoelectrics: Crystal anisotropy, conduction mechanism, and power factor

    NASA Astrophysics Data System (ADS)

    Lee, Soonil; Wilke, Rudeger H. T.; Trolier-McKinstry, Susan; Zhang, Shujun; Randall, Clive A.

    2010-01-01

    Nonstoichiometric tungsten bronze-structured ferroelectric SrxBa1-xNb2O6-δ (SBN) single crystals were found to be a promising n-type thermoelectric oxide. Thermopower anomalies were observed at the phase transition temperatures, depending on the degree of reduction as well as crystal anisotropy. Above 500 K, heavily reduced SBN crystals show high thermoelectric power factors (˜20 μW/cm K2 at 516 K) with both thermopower and electrical conductivity higher parallel to the c-axis. It is noted that the power factor increases with temperature due to the semiconducting behavior with high carrier concentration. The carrier transport mechanism also varies with the degree of reduction and temperature.

  6. Studies on various properties of pure and Li-doped Barium Hydrogen Phosphate (BHP) single crystals

    NASA Astrophysics Data System (ADS)

    Nallamuthu, D.; Selvarajan, P.; Freeda, T. H.

    2010-12-01

    Single crystals of pure and Li-doped barium hydrogen phosphate (BHP) were grown by solution method with gel technique. Various properties of the harvested crystals were studied by carrying out single crystal and powder XRD, FTIR, TG/DTA, microhardness and dielectric studies. Atomic absorption study was carried out for Li-doped BHP crystal to check the presence of Li dopants. Unit cell dimensions and diffracting planes of the grown crystals have been identified from XRD studies. Functional groups of the title compounds have been identified from FTIR studies. Density of the grown crystals was calculated using the XRD data. Thermal stability of the samples was checked by TG/DTA studies. Mechanical and dielectric characterizations of the harvested pure and Li-doped BHP crystals reveal the mechanical strength and ferroelectric transition. The observed results are reported and discussed.

  7. Electrocaloric cooling based on relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Suchaneck, Gunnar; Gerlach, Gerald

    2015-03-01

    In this work, we consider the electrocaloric effect in relaxor ferroelectrics above the temperature of the dielectric constant maximum. For the purpose of modelling, a modified Curie--Weiss law was adapted to approximate the complex physics of relaxors. The requirements to electrocaloric materials derived on this basis are fulfilled by relaxor single crystals, ceramics and high-quality thin films. Relaxor ferroelectrics exhibit a suitable electrocaloric performance starting at applied electric fields of about 25 V/μm.

  8. Unambiguous phonon mode assignment in multiferroic BiFeO3 single crystals

    NASA Astrophysics Data System (ADS)

    Beekman, Christianne; Cheong, Sang-Wook; Burch, Kenneth

    2012-02-01

    In Bismuth ferrite (BiFeO3) antiferromagnetic and ferroelectric order parameters coexist at room temperature, making this material an excellent candidate for new functionalities, such as electrical control of magnetism. Despite extensive reports on Raman scattering experiments on single crystals and thin films, controversy still remains in the observation and assignment of the phonon mode symmetries. We present polarized micro-Raman spectroscopy of single crystals ((1 0 0)cubic surface) with uniform ferroelectric polarization. Careful examination of the Raman spectra upon crystal rotation enables us to unambiguously assign the (A1, Ex and Ey) modes. We will show that ambiguity is easily introduced by slight misalignment of the crystal and that the crystal rotation is necessary to reach unambiguous mode assignment. Our method not only results in proper Raman mode assignment, which is necessary to describe the phonons critical for the multiferroic behavior, it also allows study of symmetry breaking and may provide a way to non-invasively check the ferroelectric polarization direction.

  9. Electromechanical memory effect in a ferroelectric nanoparticle-suspended liquid crystal

    NASA Astrophysics Data System (ADS)

    Basu, Rajratan

    2014-03-01

    A small quantity of BaTiO3 ferroelectric nanoparticles (FNP) was doped in a liquid crystal (LC), and the LC +FNP hybrid was found to exhibit an electromechanical memory effect in the isotropic phase. The permanent dipole moment of the FNPs causes the LC molecule to form short-range order surrounding the FNPs. This FNP-induced short-range order becomes more prominent in the isotropic phase when the global nematic order is absent. These short-range domains, being anisotropic in nature, interact with the external electric field. When the field goes off, these domains stay oriented due to the absence of the long range order in the isotropic phase, showing a hysteresis effect. The area under the hysteresis graph shows a significant pretransitional behavior on approaching the nematic phase from the isotropic phase.

  10. Beam steering experiment with two cascaded ferroelectric liquid-crystal spatial light modulators.

    PubMed

    Engström, David; Hård, Sverker; Rudquist, Per; Dhavé, Koen; Matuszczyk, Tomasz; Skeren, Marek; Löfving, Björn

    2004-03-01

    The design, construction, and evaluation of a laser beam steerer that uses two binary ferroelectric liquid-crystal (FLC) spatial light modulators (SLMs) operated in conjunction are presented. The system is characterized by having few components and is in principle lossless. Experimentally, a throughput of approximately 20% was achieved. The simple system design was achieved because of the high tilt angle FLC material used in the SLMs, which were specifically designed and manufactured for this study. By coherently imaging the first SLM onto the second SLM, pixel by pixel, we obtained an effective four-level phase structure with a phase step of 90 degrees. An appropriate alignment procedure is presented. The beam steering performance of the system is reported and analyzed.

  11. Use of ferroelectric liquid crystal panels to control state and degree of polarization in light beams.

    PubMed

    Peinado, Alba; Lizana, Angel; Campos, Juan

    2014-02-01

    We propose a new technique that is able to generate a light beam with a controlled state of polarization (SoP) and a customized degree of polarization (DoP). The technique relies on the fact that effective depolarization can be achieved by temporally averaging a time-dependent SoP. Our proposed setup is based on a ferroelectric liquid crystal panel of retardance λ/2, with a fast polarization switching capability (33 Hz). A mathematical basis describing the experiment is given. In addition, simulation data is discussed, showing the possibility of generating any SoP with full control of the DoP. Finally, to prove the potential of the invention proposed, experimental results are provided as well, reaching an experimental minimum DoP of 0.14.

  12. Effect of cadmium selenide quantum dots on the dielectric and physical parameters of ferroelectric liquid crystal

    NASA Astrophysics Data System (ADS)

    Singh, D. P.; Gupta, S. K.; Manohar, R.; Varia, M. C.; Kumar, S.; Kumar, A.

    2014-07-01

    The effect of cadmium selenide quantum dots (CdSe QDs) on the dielectric relaxation and material constants of a ferroelectric liquid crystal (FLC) has been investigated. Along with the characteristic Goldstone mode, a new relaxation mode has been induced in the FLC material due to the presence of CdSe QDs. This new relaxation mode is strongly dependent on the concentration of CdSe QDs but is found to be independent of the external bias voltage and temperature. The material constants have also been modified remarkably due to the presence of CdSe QDs. The appearance of this new relaxation phenomenon has been attributed to the concentration dependent interaction between CdSe QDs and FLC molecules.

  13. Effect of cadmium selenide quantum dots on the dielectric and physical parameters of ferroelectric liquid crystal

    SciTech Connect

    Singh, D. P.; Gupta, S. K.; Manohar, R.; Varia, M. C.; Kumar, S.; Kumar, A.

    2014-07-21

    The effect of cadmium selenide quantum dots (CdSe QDs) on the dielectric relaxation and material constants of a ferroelectric liquid crystal (FLC) has been investigated. Along with the characteristic Goldstone mode, a new relaxation mode has been induced in the FLC material due to the presence of CdSe QDs. This new relaxation mode is strongly dependent on the concentration of CdSe QDs but is found to be independent of the external bias voltage and temperature. The material constants have also been modified remarkably due to the presence of CdSe QDs. The appearance of this new relaxation phenomenon has been attributed to the concentration dependent interaction between CdSe QDs and FLC molecules.

  14. Smectic Layer Deformation of Ferroelectric Liquid Crystal Sandwiched between Polymer Walls with Anchoring Effects

    NASA Astrophysics Data System (ADS)

    Murashige, Takeshi; Fujikake, Hideo; Ikehata, Seiichiro; Sato, Fumio

    2002-05-01

    We studied smectic layer structures of ferroelectric liquid crystal (FLC) formed in elongated small spaces surrounded by molecule-aligned polymer walls and rubbed polyimide alignment layers. The polymer walls, which are parallel to the rubbing direction and vertical to the alignment layers, were formed by the photopolymerization of an aligned monomer under patterned ultraviolet light irradiation. From the observation of the alignment textures of the FLC between the polymer walls with a polarizing microscope, it was found that the smectic layer structure was changed from vertical plane bending alignment (chevron structure), as observed with a conventional surface-stabilized FLC, into horizontal plane bending, as the interval between the polymer walls decreased. It is thought that the smectic layer structure is governed by the competition between the anchoring effects of the alignment polyimide layers and the molecule-aligned polymer walls.

  15. Micro-patterned photo-aligned ferroelectric liquid crystal Fresnel zone lens.

    PubMed

    Srivastava, A K; Wang, X; Gong, S Q; Shen, D; Lu, Y Q; Chigrinov, V G; Kwok, H S

    2015-04-15

    In this Letter, we disclose a fast switchable Fresnel zone lens (FZL) by confining the ferroelectric liquid crystals (FLCs) in multiple microscopically defined photo-aligned alignment domains. The photo-alignment (PA) offers good control on the anchoring energy (W) by mean of irradiation doses (ID) and thus excellent alignment for FLCs. Two operational modes of the FLCFZL, i.e., FOCUS/OFF and FOCUS/DEFOCUS, were demonstrated. The proposed diffracting element provides fast response time, high diffraction efficiency (η), with saturated electro-optical (EO) operations up to high frequency (≈2  kHz). Thus, the proposed FLCFZLs with simple fabrication open several opportunities to improve the quality of existing devices and to find new applications.

  16. Resonant ultrasonic spectroscopy of KTa1-xNbxO3 ferroelectric relaxor crystals

    SciTech Connect

    Svitelskiy, O.; Headley, S.; Suslov, A. V.; Migliori, A.; Yong, G.; Boatner, Lynn A

    2008-08-01

    The influence of the development of a ferroelectric state on the elastic properties of KTa1-xNbxO3 relaxor crystals is explored. The high sensitivity of all elements of the elastic stiffness tensor to the polar distortions and their reorientational dynamics is, however, individual for each particular element: c11 and c44 are pimarily influenced by the reorientational motion of these distortions between neighboring (111) directions; the c12 mostly depends on the reorientations between cubic face diagonal (111) directions. Consequently, the temperature behavior of c12 demonstrates different dependence on the Nb concentration than that of c11 and c44. While in the 1.2% Nb crystal all three elastic constants clearly show their softening with the appearance of the dynamic polar distortions; in the 16% crystal this effect is strong for c11 and c44, but negligible for c12. The curves of slowness and Young's modulus within (100) crystallographic plane are presented. The linear compressibility modulus is estimated. The value of the Debye temperature is estimated to be approximately 592 K.

  17. Peculiarities of electro-optic properties of the ferroelectric particles-liquid crystal colloids

    NASA Astrophysics Data System (ADS)

    Ibragimov, T. D.; Imamaliyev, A. R.; Bayramov, G. M.

    2016-04-01

    Influence of ferroelectric barium titanate particles on electro-optic properties of the liquid crystal (LC) 4-cyano-4'-pentylbiphenyl (5CB) with positive dielectric anisotropy and the LC mixture (H37) consisting of 4-methoxybezylidene-4'-butylaniline and 4-ethoxybezylidene-4'-butylaniline with negative dielectric anisotropy was investigated. It was shown that a presence of particles (1 wt%) in 5CB and H37 decreased the clearing temperature from 35.2 °C to 32.4°C and from 61.2°C to 60.1°C, respectively. The threshold voltage of the Freedericksz effect became 0.3 V for the BaTiO3-5CB colloid while the beginning of this effect for the pure 5CB was observed at 2.1 V. The threshold voltage of the Freedericksz effect increased from 2.8 V to up 3.1 V at additive of particles in H37. A rise time of the BaTiO3-5CB colloid improved while a decay time worsened in comparison with the pure 5CB at all applied voltages. The inverse trends were observed for the H37 matrix, namely, a rise time worsened and a decay time improved. Among other things, the pecularities of Williams' domain formation (WDF) were also investigated in the colloid based on the H37 matrix. It was established that the WDF voltage decreased, a rise time increased and a decay time decreased in comparison with the pure H37. Experimental results are explained by appearance of local electric fields near the polarized ferroelectric particles at application of external electric field and an existence of the additional obstacles (particles) for movement of ions.

  18. Ferroelectric domain wall motion induced by polarized light

    PubMed Central

    Rubio-Marcos, Fernando; Del Campo, Adolfo; Marchet, Pascal; Fernández, Jose F.

    2015-01-01

    Ferroelectric materials exhibit spontaneous and stable polarization, which can usually be reoriented by an applied external electric field. The electrically switchable nature of this polarization is at the core of various ferroelectric devices. The motion of the associated domain walls provides the basis for ferroelectric memory, in which the storage of data bits is achieved by driving domain walls that separate regions with different polarization directions. Here we show the surprising ability to move ferroelectric domain walls of a BaTiO3 single crystal by varying the polarization angle of a coherent light source. This unexpected coupling between polarized light and ferroelectric polarization modifies the stress induced in the BaTiO3 at the domain wall, which is observed using in situ confocal Raman spectroscopy. This effect potentially leads to the non-contact remote control of ferroelectric domain walls by light. PMID:25779918

  19. Additive manufacturing of micrometric crystallization vessels and single crystals

    PubMed Central

    Halevi, Oded; Jiang, Hui; Kloc, Christian; Magdassi, Shlomo

    2016-01-01

    We present an all-additive manufacturing method that is performed at mild conditions, for the formation of organic single crystals at specific locations, without any photolithography prefabrication process. The method is composed of two steps; inkjet printing of a confinement frame, composed of a water soluble electrolyte. Then, an organic semiconductor solution is printed within the confinement to form a nucleus at a specific location, followed by additional printing, which led to the growth of a single crystal. The specific geometry of the confinement enables control of the specific locations of the single crystals, while separating the nucleation and crystal growth processes. By this method, we printed single crystals of perylene, which are suitable for the formation of OFETs. Moreover, since this method is based on a simple and controllable wet deposition process, it enables formation of arrays of single crystals at specific locations, which is a prerequisite for mass production of active organic elements on flexible substrates. PMID:27830827

  20. Additive manufacturing of micrometric crystallization vessels and single crystals.

    PubMed

    Halevi, Oded; Jiang, Hui; Kloc, Christian; Magdassi, Shlomo

    2016-11-10

    We present an all-additive manufacturing method that is performed at mild conditions, for the formation of organic single crystals at specific locations, without any photolithography prefabrication process. The method is composed of two steps; inkjet printing of a confinement frame, composed of a water soluble electrolyte. Then, an organic semiconductor solution is printed within the confinement to form a nucleus at a specific location, followed by additional printing, which led to the growth of a single crystal. The specific geometry of the confinement enables control of the specific locations of the single crystals, while separating the nucleation and crystal growth processes. By this method, we printed single crystals of perylene, which are suitable for the formation of OFETs. Moreover, since this method is based on a simple and controllable wet deposition process, it enables formation of arrays of single crystals at specific locations, which is a prerequisite for mass production of active organic elements on flexible substrates.

  1. Additive manufacturing of micrometric crystallization vessels and single crystals

    NASA Astrophysics Data System (ADS)

    Halevi, Oded; Jiang, Hui; Kloc, Christian; Magdassi, Shlomo

    2016-11-01

    We present an all-additive manufacturing method that is performed at mild conditions, for the formation of organic single crystals at specific locations, without any photolithography prefabrication process. The method is composed of two steps; inkjet printing of a confinement frame, composed of a water soluble electrolyte. Then, an organic semiconductor solution is printed within the confinement to form a nucleus at a specific location, followed by additional printing, which led to the growth of a single crystal. The specific geometry of the confinement enables control of the specific locations of the single crystals, while separating the nucleation and crystal growth processes. By this method, we printed single crystals of perylene, which are suitable for the formation of OFETs. Moreover, since this method is based on a simple and controllable wet deposition process, it enables formation of arrays of single crystals at specific locations, which is a prerequisite for mass production of active organic elements on flexible substrates.

  2. Ferroelectric C* phase induced in a nematic liquid crystal matrix by a chiral non-mesogenic dopant

    NASA Astrophysics Data System (ADS)

    Pozhidaev, E. P.; Torgova, S. I.; Barbashov, V. A.; Minchenko, M. V.; Sulyanov, S. N.; Dorovatovskii, P. V.; Ostrovskii, B. I.; Strigazzi, A.

    2015-02-01

    We report on a ferroelectric chiral smectic C (C*) phase obtained in a mixture of a nematic liquid crystal (NLC) and a chiral nonmesogenic dopant. The existence of C* phase was proven by calorimetric, dielectric and optical measurements, and also by X-rays analysis. The smectic C* which is obtained in such a way can flow, allowing to restore the ferroelectric liquid crystal layer structure in the electro-optical cells after action of the mechanical stress, as it happens with the cells filled with NLC. The proposed method of obtaining smectic C* material allows us to create innovative electro-optical cell combining the advantages of NLC (mechanical resilience) and smectic C* (high switching speed).

  3. Ferroelectric Tungsten Bronze Bulk Crystals and Epitaxial Thin Films for Electro-Optic Device Applications

    DTIC Science & Technology

    1984-07-01

    improved, they show a considerable enhancement in electro - optic and photorefractive properties, specifically for Ce(3+)-doped SBN:60 crystals. The...concentration of impurity ions increased. Undoped SBN:60 single crystals have also been grown and they are almost striation-free and exhibit excellent electro - optic properties.

  4. Crystal structure and polarization hysteresis properties of ferroelectric BaTiO3 thin-film capacitors on (Ba,Sr)TiO3-buffered substrates

    NASA Astrophysics Data System (ADS)

    Maki, Hisashi; Noguchi, Yuji; Kutsuna, Kazutoshi; Matsuo, Hiroki; Kitanaka, Yuuki; Miyayama, Masaru

    2016-10-01

    Ferroelectric BaTiO3 (BT) thin-film capacitors with a buffer layer of (Ba1- x Sr x )TiO3 (BST) have been fabricated on (001) SrTiO3 (STO) single-crystal substrates by a pulsed laser deposition method, and the crystal structure and polarization hysteresis properties have been investigated. X-ray diffraction reciprocal space mapping shows that the BST buffer effectively reduces the misfit strain relaxation of the BT films on SrRuO3 (SRO) electrodes. The BT capacitor with the SRO electrodes on the BST (x = 0.3) buffer exhibits a well-saturated hysteresis loop with a remanent polarization of 29 µC/cm2. The hysteresis loop displays a shift toward a specific field direction, which is suggested to stem from the flexoelectric coupling between the out-of-plane polarization and the strain gradient adjacent to the bottom interface.

  5. Twisted ferroelectric liquid crystals dynamic behaviour modification under electric field: A Mueller matrix polarimetry approach using birefringence

    NASA Astrophysics Data System (ADS)

    Babilotte, P.; Nunes Henrique Silva, V.; Sathaye, K.; Dubreuil, M.; Rivet, S.; Dupont, L.; de Bougrenet de la Tocnaye, J. L.; Le Jeune, B.

    2014-01-01

    A low frequency and high amplitude rectangular voltage V has been applied during different increased duration to Twisted Surface Stabilized Ferroelectric Liquid crystal (TwFLC) samples in which the alignment layers of the two substrates were rubbed along two different directions between 0° and 90°. The optical bistability properties have been evaluated using the specific Mueller Matrix formalism that allows a simultaneous access, through a single-shot measurement, to different polarimetric coefficients. In this new approach, the ellipticity ɛR and the azimuthal αR polarimetric parameters, extracted from the birefringence Mueller Matrix MR will be considered in priority. Several significant parameters, such as the horizontal offset ΔV, the degree of asymmetry DA, the characteristic area S of the hysteresis loop, are used to characterize the degradation observed into the hysteretic behaviour of the samples, for different values of ψ, at different duration T of exposure to V, before reaching the so-called stripes regime, giving a new experimental point of view concerning the evolution of the dynamic properties of the samples studied. The αR(V) and the ɛR(V) hysteresis loops are specifically examined. Static mapping related to ɛR(T) is given too. Among the different possible physical origins of the observed degradation, the in-plane anchoring energy contribution will be particularly examined, and a theoretical model is proposed that also gives access to different physical parameters, through a new approach.

  6. Temperature and electric field-induced phase transitions in (1 - x)Pb(Mg1/3Nb2/3)O3- xPbTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Shabbir, Ghulam; Ko, Jae-Hyeon

    2017-03-01

    Field-induced phase transitions in [111]- and [110]-oriented relaxor ferroelectric (1 - x)Pb(Mg1/3Nb2/3)O3- xPbTiO3 (PMN-PT) single crystals in the morphotropic phase boundary (MPB) composition range were examined through temperature-dependent complex capacitance measurements. Two first-order phase transitions from paraelectric cubic to ferroelectric tetragonal and then to ferroelectric rhombohedral phases were observed in the unpoled crystal. Additional weak dielectric anomalies were observed at a temperature of 40 °C (in both crystals) and 90 °C (in [110] crystals) in the poled samples. These weak anomalies disappeared when cooling the crystal from higher temperature but within the ferroelectric tetragonal phase. The new anomalies were attributed to the formation of field-induced metastable phases, which were unstable with temperature modulation.

  7. Banded Structure and Domain Arrangements in PbTiO3 Single Crystals

    NASA Astrophysics Data System (ADS)

    Chou, Chen-Chia; Chen, Cheng-Sao

    1998-09-01

    In the present work we report the ferroelectric domain arrangements and characteristics of banded structures observed in flux-grown PbTiO3 single crystals. Investigations of etched crystals indicate that most of the specimens show banded structures which may correspond to surface relief characteristics of as-grown crystals. Banded structures, which are different from domain structures, possess structural characteristics similar to those of martensite variants in various alloys and ceramics. The stresses produced during transformation were relieved by the formation of the banded structures and the 90° domain structures, suggesting that the band structures and 90° domains are the products of self-accommodation in as-grown PbTiO3 crystals during the cubic/tetragonal (C/T) transformation. Image characteristics imply that banded-structure-induced domain intersections may store high strain energy in lead titanate crystals and therefore hinder polarization switching of the crystals.

  8. Growth of Ba(Ti 1- xZr x)O 3 single crystals by the laser heated pedestal growth technique

    NASA Astrophysics Data System (ADS)

    Zhi, Yu; Guo, Ruyan; Bhalla, A. S.

    2001-12-01

    Single crystals of the ferroelectric Ba(Ti 1- xZr x)O 3 ( x=0.05 and 0.08) were grown by the laser heated pedestal growth (LHPG) technique. The perovskite structure of the crystals was identified by the X-ray diffraction technique. Crystals were examined by Laue patterns and scanning electron microscopy (SEM), which indicated that the single crystals were of good crystallinity and compositional homogeneity. The anisotropic dielectric and piezoelectric behavior was characterized. The Ba(Ti 1- xZr x)O 3 single crystals possessed a high-level hysteresis-free electromechanical strain and are promising lead-free ferroelectric crystals for the piezoelectric transducer applications.

  9. Correlation between piezoresponse nonlinearity and hysteresis in ferroelectric crystals at nanoscale

    SciTech Connect

    Kalinin, Sergei V.; Jesse, Stephen; Yang, Yaodong; Li, Linglong; Liu, Zhengchun; Vasudevan, Rama K.

    2016-04-27

    Here, the nonlinear response of a ferroic to external fields has been studied for decades, garnering interest for both understanding fundamental physics, as well as technological applications such as memory devices. Yet, the behavior of ferroelectrics at mesoscopic regimes remains poorly understood, and the scale limits of theories developed for macroscopic regimes are not well tested experimentally. Here, we test the link between piezo-nonlinearity and local piezoelectric strain hysteresis, via AC-field dependent measurements in conjunction with first order reversal curve (FORC) measurements on (K,Na)NbO3 crystals with band-excitation piezoelectric force microscopy. The correlation coefficient between nonlinearity amplitude and the FORC of the polarization switching shows a clear decrease in correlation with increasing AC bias, suggesting the impact of domain wall clamping on the DC measurement case. Further, correlation of polynomial fitting terms from the nonlinear measurements with the hysteresis loop area reveals that the largest correlations are reserved for the quadratic terms, which is expected for irreversible domain wall motion contributions that impact both piezoelectric behavior as well as minor loop formation. These confirm the link between local piezoelectric nonlinearity, domain wall motion and minor loop formation, and suggest that existing theories (such as Preisach) are applicable at these length scales, with associated implications for future nanoscale devices.

  10. Correlation between piezoresponse nonlinearity and hysteresis in ferroelectric crystals at nanoscale

    DOE PAGES

    Kalinin, Sergei V.; Jesse, Stephen; Yang, Yaodong; ...

    2016-04-27

    Here, the nonlinear response of a ferroic to external fields has been studied for decades, garnering interest for both understanding fundamental physics, as well as technological applications such as memory devices. Yet, the behavior of ferroelectrics at mesoscopic regimes remains poorly understood, and the scale limits of theories developed for macroscopic regimes are not well tested experimentally. Here, we test the link between piezo-nonlinearity and local piezoelectric strain hysteresis, via AC-field dependent measurements in conjunction with first order reversal curve (FORC) measurements on (K,Na)NbO3 crystals with band-excitation piezoelectric force microscopy. The correlation coefficient between nonlinearity amplitude and the FORC ofmore » the polarization switching shows a clear decrease in correlation with increasing AC bias, suggesting the impact of domain wall clamping on the DC measurement case. Further, correlation of polynomial fitting terms from the nonlinear measurements with the hysteresis loop area reveals that the largest correlations are reserved for the quadratic terms, which is expected for irreversible domain wall motion contributions that impact both piezoelectric behavior as well as minor loop formation. These confirm the link between local piezoelectric nonlinearity, domain wall motion and minor loop formation, and suggest that existing theories (such as Preisach) are applicable at these length scales, with associated implications for future nanoscale devices.« less

  11. Polarimeter with two ferroelectric liquid-crystal modulators attached to the Yunnan solar tower.

    PubMed

    Xu, Chenglin; Qu, Zhongquan; Zhang, Xiaoyu; Jin, Chunlan; Yan, Xiaoli

    2006-11-20

    A polarimeter to be mounted on the Yunnan solar tower is described. It features the ability to simultaneously measure the magnetic fields of the solar photosphere and chromosphere by analyzing the Stokes spectra of those magnetosensitive lines forming in the two regions with very high efficiency of polarization measurement. The polarimeter consists of two ferroelectric liquid crystals and one lambda/4 wave plate before a polarizing beam splitter. The achromatism of the design is emphasized to get the maximum combination efficiency over a spectral range from 5000 to 6000 A. For the used solar absorption lines MgI517.27, FeI525.06, FeI630.15, and FeI630.25 nm, the design gives theoretical efficiencies of polarization measurements, which are 0.999, 1.0, 0.943, and 0.943, respectively. A comparison with other reference polarimeters, such as the Synoptic Optical Long-term Investigation of the Sun, the Tenerife infrared polarimeter, and the La Palma Stokes Polarimeter, is carried out.

  12. The PSDAVLL signal detection with synchronous ferroelectric liquid crystal switching as a laser frequency stabilization method

    NASA Astrophysics Data System (ADS)

    Dudzik, G.; Rzepka, J.; Abramski, K. M.

    2016-12-01

    In this paper we present the DAVLL (Dichroic Atomic Vapor Laser Lock) signals detection method for laser frequency stabilization which has been improved by synchronous detection system based on the surface-stabilized ferroelectric liquid crystal (SSFLC). The SSFLC cell is a polarization switch and quarter waveplate component and it replaces the well-known two-photodiode detection configuration known as the balanced polarimeter. The presented polarization switching dichroic atomic vapor laser lock technique (PSDAVLL) was practically used in VCSEL-based frequency stabilization system with vapor isotopes (85,87Rb) rubidium cell. The applied PSDAVLL method has allowed us to obtain a frequency stability of 2.7 × 10-9 and a reproducibility of 1.2 × 10-8, with a dynamic range ratio (DNR) of detected signals of around 81.4 dB, what is 9.6 dB better than obtained in the balanced polarimeter configuration. The described PSDAVLL technique was compared with 3-f (on the 3rd harmonic) and passive frequency stabilization methods. Additionally, the presented setup consists only one-photodiode detection path what reduces parasitic phenomena like offsets between photodiode amplifiers, amplifier gain changes due to ambient conditions, aging effects of electronic components etc. as a consequence leads to better frequency reproducibility, stabilization accuracy and less detection system sensitivity to ambient condition changes.

  13. Ferroelectric response in an achiral non-symmetric bent liquid crystal:C12C10

    NASA Astrophysics Data System (ADS)

    Subrahmanyam, S. V.; Chalapathi, P. V.; Mahabaleshwara, S.; Srinivasulu, M.; George, A. K.; Potukuchi, D. M.

    2014-10-01

    An achiral Non-Symmetric Bent Liquid Crystal (BLC) with a Oxadiazole based hetero cyclic central moiety, abbreviated as C12C10 viz., dodecyl[4-{5-(4‧-decyloxy)biphenyl-4-yl}-1,2,4-oxadiazol-3-yl]benzoate, exhibiting FerroElectric (FE) response is reported. Product is confirmed by 1H NMR, 13C NMR and elemental analysis. Characterization of BLC phases is carried out by Polarized Optical Microscopy (POM), Differential Scanning Calorimetry (DSC), Spontaneous Polarization (PS) and Low Frequency (10 Hz-10 MHz) Dielectric Relaxation studies. C12C10 exhibits enantiotropic LC SmA, FE B2, SmG, SmE phase variance. I-SmA, B2-SmG and SmG-SmE transitions are of first order nature. FE B2 phases exhibits a moderate PS of 80 nC cm-2. B2 phase exhibits Curie-Weiss behavior to confirm FE nature. Off-centered low frequency (KHz) dispersion infers a scissor mode and a high frequency (MHz) mode to reflect the distinct time-scale response. Dielectric Dispersion is relatively susceptible in lower frequency KHz region. Arrhenius shift in Relaxation Frequency (fR) infers higher activation energy (Ea) in non-FE phases for HF mode and lower value for KHz mode. Trends of fR, dielectric strength Δε, α-parameter and Ea are discussed in view of the data reported in other LC compounds.

  14. Correlation between piezoresponse nonlinearity and hysteresis in ferroelectric crystals at the nanoscale

    NASA Astrophysics Data System (ADS)

    Li, Linglong; Yang, Yaodong; Liu, Zhengchun; Jesse, Stephen; Kalinin, Sergei V.; Vasudevan, Rama K.

    2016-04-01

    The nonlinear response of a ferroic to external fields has been studied for decades, garnering interest for both understanding fundamental physics, as well as technological applications such as memory devices. Yet, the behavior of ferroelectrics at mesoscopic regimes remains poorly understood, and the scale limits of theories developed for macroscopic regimes are not well tested experimentally. Here, we test the link between piezo-nonlinearity and local piezoelectric strain hysteresis, via AC-field dependent measurements in conjunction with hysteresis measurements with varying voltage windows on (K,Na)NbO3 crystals with band-excitation piezoelectric force microscopy. The correlation coefficient between nonlinearity amplitude and the amplitude during hysteresis loop acquisition shows a clear decrease with increasing AC bias. Further, correlation of polynomial fitting terms from the nonlinear measurements with the hysteresis loop area reveals that the largest correlations are reserved for the quadratic terms, which is expected for irreversible domain wall motion contributions that impact both piezoelectric behavior as well as minor loop formation. This study suggests applicability at local length scales of fundamental principles of Rayleigh behavior, with associated implications for future nanoscale ferroic devices.

  15. Distortion and unwinding of the helical structure in polymer-stabilized short-pitch ferroelectric liquid crystal.

    PubMed

    Petit, M; Daoudi, A; Ismaili, M; Buisine, J M

    2006-07-01

    We report the effect of an anisotropic polymer network formed from an achiral photoreactive monomer in a short-pitch chiral SmC* phase on the distortion and the unwinding of the helical structure of the ferroelectric phase. The electro-optical behaviour and ferroelectric properties were experimentally determined for films containing various polymer concentrations. The critical field, E(u), for the transition from the distorted structure to the homogeneous state was measured as a function of polymer concentration. A linear increase of E(u) versus polymer concentration was observed, showing that the helical structure of the short-pitch SmC* phase was stabilized by the polymer network. This behaviour was expected to be a consequence of the increase of the apparent elastic constants of the ferroelectric liquid crystal stabilized by the anisotropic polymer network films. The polymer network morphology was investigated using atomic-force microscopy, revealing a twisted structure of the polymer fibers. This twisted structure was transferred onto a polymer network during the polymerization process within a short-pitch SmC* phase. The increase of the apparent elasticity can then be interpreted by a strong interaction between polymer network and the liquid-crystal molecules. From our experimental data, the coupling coefficient, W(p), characterizing this interaction was evaluated for all studied polymer concentrations.

  16. Synthesis and structural characterization of a single-crystal to single-crystal transformable coordination polymer.

    PubMed

    Tian, Yuyang; Allan, Phoebe K; Renouf, Catherine L; He, Xiang; McCormick, Laura J; Morris, Russell E

    2014-01-28

    A single-crystal to single-crystal transformable coordination polymer compound was hydrothermally synthesized. The structural rearrangement is induced by selecting a ligand that contains both strong and weaker coordinating groups. Both hydrated and dehydrated structures were determined by single crystal X-ray analysis.

  17. Ames Lab 101: Single Crystal Growth

    SciTech Connect

    Schlagel, Deborah

    2013-09-27

    Ames Laboratory scientist Deborah Schlagel talks about the Lab's research in growing single crystals of various metals and alloys. The single crystal samples are vital to researchers' understanding of the characteristics of a materials and what gives these materials their particular properties.

  18. Confinement stabilises single crystal vaterite rods.

    PubMed

    Schenk, Anna S; Albarracin, Eduardo J; Kim, Yi-Yeoun; Ihli, Johannes; Meldrum, Fiona C

    2014-05-11

    Single-crystals of vaterite, the least-stable anhydrous polymorph of CaCO3, are rare in biogenic and synthetic systems. We here describe the synthesis of high aspect ratio single crystal vaterite rods under additive-free conditions by precipitating CaCO3 within the cylindrical pores of track-etch membranes.

  19. Ultratough single crystal boron-doped diamond

    DOEpatents

    Hemley, Russell J [Carnegie Inst. for Science, Washington, DC ; Mao, Ho-Kwang [Carnegie Inst. for Science, Washington, DC ; Yan, Chih-Shiue [Carnegie Inst. for Science, Washington, DC ; Liang, Qi [Carnegie Inst. for Science, Washington, DC

    2015-05-05

    The invention relates to a single crystal boron doped CVD diamond that has a toughness of at least about 22 MPa m.sup.1/2. The invention further relates to a method of manufacturing single crystal boron doped CVD diamond. The growth rate of the diamond can be from about 20-100 .mu.m/h.

  20. Ames Lab 101: Single Crystal Growth

    ScienceCinema

    Schlagel, Deborah

    2016-07-12

    Ames Laboratory scientist Deborah Schlagel talks about the Lab's research in growing single crystals of various metals and alloys. The single crystal samples are vital to researchers' understanding of the characteristics of a materials and what gives these materials their particular properties.

  1. Research on the Crystal Growth and Dielectric Properties of High Permittivity Ferroelectric Materials.

    DTIC Science & Technology

    1985-07-01

    tungsten bronzes such as potassium lithium niobate (KLN) and barium strontium potassium sodium niohate (BSKNN) have been prepared and studied to elucidate...the volatilization of potassium during growth, and the crystals after crack when grown along the c-axis. This cracking problem has been nearly...temperature as soon as suitable samples are fabricated. 3.2.3 Millimeter Wave Dielectric Properties of Single Crystal KLN Potassium lithium niobate

  2. Electromechanical properties of tetragonal Pb(In(12)Nb(12))O(3)-Pb(Mg(13)Nb(23))O(3)-PbTiO(3) ferroelectric crystals.

    PubMed

    Li, Fei; Zhang, Shujun; Xu, Zhuo; Wei, Xiaoyong; Luo, Jun; Shrout, Thomas R

    2010-03-01

    The ferroelectric, dielectric, elastic, piezoelectric, and electromechanical properties of tetragonal Pb(In(12)Nb(12))O(3)-Pb(Mg(13)Nb(23))O(3)-PbTiO(3) (PIN-PMN-PT) crystals were investigated. The single domain piezoelectric coefficients d(33), d(15), and d(31) were found to be 530, 2350, and -200 pCN, respectively, with electromechanical coupling factors k(33), k(15), and k(31) being on the order of 0.84, 0.85, and 0.58. The mechanical quality factor Q for longitudinal mode was found to be >700, with high coercive field (E(c)) being on the order of 10 kVcm. The temperature and dc bias electric-field characteristics of single domain tetragonal PIN-PMN-PT crystals were also investigated. In contrast to [001] oriented domain engineered rhombohedral crystals, tetragonal PIN-PMN-PT crystals exhibited broader temperature usage range and higher thermalelectric field stability, with improved coercive field and mechanical quality factor.

  3. Structure, frequency dependent dielectric properties and domain configuration of PMN-PFN-PT single crystal

    NASA Astrophysics Data System (ADS)

    Luo, Nengneng; Li, Qiang; Yan, Qingfeng; Zhang, Yiling; Xia, Zhiguo; Chu, Xiangcheng

    2014-09-01

    Pb(Mg1/3Nb2/3)O3-Pb(Fe1/2Nb1/2)O3-PbTiO3 (PMN-PFN-PT) single crystal was grown successfully from high temperature solution by slow cooling method. Structure, frequency dependent dielectric properties and domain configuration of [0 0 1]-oriented single crystal have been investigated. X-ray diffraction analysis showed that the as-grown single crystal had a pure perovskite structure with tetragonal symmetry at room temperature. The temperature dependent dielectric permittivity showed only one dielectric anomaly, indicating the ferroelectric-paraelectric phase transition. According to the modified Curie-Weiss relationship, as-grown PMN-PFN-PT single crystal was in an intermediate state between normal and relaxor ferroelectrics. Dielectric permittivity and loss of [0 0 1]-oriented PMN-PFN-PT single crystal at room temperature decreased sharply with increasing frequency, which were different from those of PMN-PT65/35 single crystal. Domain configuration of [0 0 1]-oriented PMN-PFN-PT single crystal was observed for the first time by using a polarized light microscopy (PLM). The extinction of 90° domains at P/A:0° revealed a tetragonal structure. Domains along (0 0 1) face exhibited a straight stripe-like morphology with domain size on the scale of 10 μm in average, combining with some much smaller domains about 3-5 μm in width at the intersection of domain blocks which helps to minimize its total energy.

  4. Method of making single crystal fibers

    NASA Technical Reports Server (NTRS)

    Westfall, Leonard J. (Inventor)

    1990-01-01

    Single crystal fibers are made from miniature extruded ceramic feed rods. A decomposable binder is mixed with powders to inform a slurry which is extruded into a small rod which may be sintered, either in air or in vacuum, or it may be used in the extruded and dried condition. A pair of laser beams focuses onto the tip of the rod to melt it thereby forming a liquid portion. A single crystal seed fiber of the same material as the feed rod contacts this liquid portion to establish a zone of liquid material between the feed rod and the single crystal seed fiber. The feed rod and the single crystal feed fiber are moved at a predetermined speed to solidify the molten zone onto the seed fiber while simultaneously melting additional feed rod. In this manner a single crystal fiber is formed from the liquid portion.

  5. Pyroelectric properties and electrocaloric effect in TGS1-xPx single crystals

    NASA Astrophysics Data System (ADS)

    Sampathkumar, P.; Srinivasan, K.

    2016-10-01

    Triglycine sulfate (TGS) single crystals modified with phosphoric acid (TGS1-xPx) have been grown by slow evaporation technique at room temperature. Lattice parameters were identified by using single crystal x-ray diffractometer. The dielectric, pyroelectric, ferroelectric properties and electrocaloric effect have been investigated. Curie temperature of grown crystals was determined from dielectric constant measurements at various temperatures at a frequency of 1 kHz. The Curie temperature is found decreased for the TGS single crystals with the addition of phosphoric acid. Room temperature P-E hysteresis loops of TGS1-xPx single crystals are presented. The values of coercive field Ec, spontaneous polarization Ps and internal bias field Eb were obtained from the hysteresis loops. Discussion on pyroelectric properties as a function of temperature and applied electric field is presented. Figure of merits (FOMs) were determined to study the pyroelectric performance of the grown crystals. Among all compositions of x, x = 0.2 (i.e., TGS0.8P0.2) single crystals exhibited the largest pyroelectric coefficient and pyroelectric figure of merit at room temperature. From the above investigations the electrocaloric temperature change, ΔT of TGS1-xPx single crystals at selected applied fields and temperatures are obtained by indirect method and discussed.

  6. Single-crystal silicon optical fiber by direct laser crystallization

    SciTech Connect

    Ji, Xiaoyu; Lei, Shiming; Yu, Shih -Ying; Cheng, Hiu Yan; Liu, Wenjun; Poilvert, Nicolas; Xiong, Yihuang; Dabo, Ismaila; Mohney, Suzanne E.; Badding, John V.; Gopalan, Venkatraman

    2016-12-05

    Semiconductor core optical fibers with a silica cladding are of great interest in nonlinear photonics and optoelectronics applications. Laser crystallization has been recently demonstrated for crystallizing amorphous silicon fibers into crystalline form. Here we explore the underlying mechanism by which long single-crystal silicon fibers, which are novel platforms for silicon photonics, can be achieved by this process. Using finite element modeling, we construct a laser processing diagram that reveals a parameter space within which single crystals can be grown. Utilizing this diagram, we illustrate the creation of single-crystal silicon core fibers by laser crystallizing amorphous silicon deposited inside silica capillary fibers by high-pressure chemical vapor deposition. The single-crystal fibers, up to 5.1 mm long, have a very welldefined core/cladding interface and a chemically pure silicon core that leads to very low optical losses down to ~0.47-1dB/cm at the standard telecommunication wavelength (1550 nm). Furthermore, tt also exhibits a photosensitivity that is comparable to bulk silicon. Creating such laser processing diagrams can provide a general framework for developing single-crystal fibers in other materials of technological importance.

  7. Single-crystal silicon optical fiber by direct laser crystallization

    DOE PAGES

    Ji, Xiaoyu; Lei, Shiming; Yu, Shih -Ying; ...

    2016-12-05

    Semiconductor core optical fibers with a silica cladding are of great interest in nonlinear photonics and optoelectronics applications. Laser crystallization has been recently demonstrated for crystallizing amorphous silicon fibers into crystalline form. Here we explore the underlying mechanism by which long single-crystal silicon fibers, which are novel platforms for silicon photonics, can be achieved by this process. Using finite element modeling, we construct a laser processing diagram that reveals a parameter space within which single crystals can be grown. Utilizing this diagram, we illustrate the creation of single-crystal silicon core fibers by laser crystallizing amorphous silicon deposited inside silica capillarymore » fibers by high-pressure chemical vapor deposition. The single-crystal fibers, up to 5.1 mm long, have a very welldefined core/cladding interface and a chemically pure silicon core that leads to very low optical losses down to ~0.47-1dB/cm at the standard telecommunication wavelength (1550 nm). Furthermore, tt also exhibits a photosensitivity that is comparable to bulk silicon. Creating such laser processing diagrams can provide a general framework for developing single-crystal fibers in other materials of technological importance.« less

  8. A nonvolatile memory device made of a ferroelectric polymer gate nanodot and a single-walled carbon nanotube.

    PubMed

    Son, Jong Yeog; Ryu, Sangwoo; Park, Yoon-Cheol; Lim, Yun-Tak; Shin, Yun-Sok; Shin, Young-Han; Jang, Hyun Myung

    2010-12-28

    We demonstrate a field-effect nonvolatile memory device made of a ferroelectric copolymer gate nanodot and a single-walled carbon nanotube (SW-CNT). A position-controlled dip-pen nanolithography was performed to deposit a poly(vinylidene fluoride-ran-trifluoroethylene) (PVDF-TrFE) nanodot onto the SW-CNT channel with both a source and drain for field-effect transistor (FET) function. PVDF-TrFE was chosen as a gate dielectric nanodot in order to efficiently exploit its bipolar chemical nature. A piezoelectric force microscopy study confirmed the canonical ferroelectric responses of the PVDF-TrFE nanodot fabricated at the center of the SW-CNT channel. The two distinct ferroelectric polarization states with the stable current retention and fatigue-resistant characteristics make the present PVDF-TrFE-based FET suitable for nonvolatile memory applications.

  9. Single crystal PMN-PT/epoxy 1-3 composite for energy-harvesting application.

    PubMed

    Ren, Kailiang; Liu, Yiming; Geng, Xuecang; Hofmann, Heath F; Zhang, Qiming M

    2006-03-01

    One key parameter in using electroactive materials to harvest electric energy from mechanical sources is the energy conversion efficiency. Recently, it was shown that, in the relaxor ferroelectric PMN-PT single crystals, a very high longitudinal electromechanical coupling factor (>90%) can be obtained. This paper investigates energy harvesting using 1-3 composites of PMN-PT single crystals in a soft epoxy matrix. It is shown that 1-3 composites enable the single crystals operating in the longitudinal mode to achieve high efficiency for energy harvesting, and the soft-polymer, matrix-supported single-crystal rods maintain high mechanical integrity under different external loads. For comparison, 1-3 composites with piezoceramic PZT also are investigated in energy-harvesting applications, and the results show that the high coupling factor of single crystal PMN-PT 1-3 composites leads to much higher electric energy output for similar mechanical energy input. The harvested energy density of 1-3 composite with single crystal (22.1 mW/cm3 under a stress of 40.4 MPa) is about twice of that harvested with PZT ceramic 1-3 composite (12 mW/cm3 under a stress of 39 MPa). At a higher stress level, the harvested-energy density of 1-3 PMN-PT single crystal composite can reach 96 mW/cm3.

  10. Phase transitions in potassium ammonium dihydrogen phosphate single crystals

    NASA Astrophysics Data System (ADS)

    Bromberek, Marek

    An apparatus for growing single crystals from aqueous solution by the slow evaporation method was constructed. Mixed crystals of K1-x(NH 4)xH2PO4 (KADP) with (NH4)H 2PO4 (ADP) fractions of 0.021 and 0.12 were successfully grown. Their composition was determined by means of the x-ray powder diffraction method. This analysis also suggests that those crystals are a mixture of two phases even at room temperature. The details of the structure of the additional phase could not be determined. The dielectric constant epsilon of the mixed crystals as well as pure KH2PO4 (KDP) was measured along the polar axis in the temperature range from 20 K to 300 K. The frequency range of the applied electric field was from 100 Hz to 10 MHz. The data were analyzed by means of the standard Landau theory of phase transitions with coupling terms reflecting the interaction between the electric and elastic degrees of freedom. The temperature dependence of epsilon follows a typical Curie-Weiss behavior in the range of approximately 30 K aboveTc for all crystals studied. The value of the critical temperature decreases with increasing ammonium ion content in agreement with previously published results. The analysis of the frequency dependence of the dielectric susceptibility clearly indicates the existence of two dispersion processes: resonant and relaxational. The former is attributed to the piezoelectric activity of all the crystals studied. The latter is the result of the response of the permanent dipole moments present in ferroelectric crystals to the applied electric field. In the case of mixed crystals the relaxational dispersion is characterized by a distribution of relaxation times. Its mean relaxation time as well as its width increases with decreasing T. This is a typical behavior for mixed crystals for which the two end members of the solid solution in their pure form undergo ferroelectric and antiferroelectric phase transitions, respectively. This behavior is a result of competing

  11. Critical slowing down and elastic anomaly of uniaxial ferroelectric Ca0.28Ba0.72Nb2O6 crystals with tungsten bronze structure

    NASA Astrophysics Data System (ADS)

    Suzuki, K.; Matsumoto, K.; Dec, J.; Łukasiewicz, T.; Kleemann, W.; Kojima, S.

    2014-08-01

    The ferroelectric phase transition of uniaxial Ca0.28Ba0.72Nb2O6 single crystals with a moderate effective charge disorder was investigated by Brillouin scattering to clarify the dynamic properties. In the tetragonal paraelectric phase a remarkable softening of the sound velocity of the longitudinal acoustic mode and a significant increase in the sound attenuation were observed close to the Curie temperature TC=527K. The intermediate temperature T* ˜640K and the Burns temperature TB ˜790K were determined from the temperature variation in the sound attenuation. The intense broad central peak (CP) caused by polarization and strain fluctuations due to polar nanoregions was clearly observed in the vicinity of TC. The relaxation time determined by the CP width clearly shows critical slowing down towards TC, reflecting a weakly first-order phase transition under weak random fields.

  12. Wavelength-compensated color Fourier diffractive optical elements using a ferroelectric liquid crystal on silicon display and a color-filter wheel.

    PubMed

    Martínez, José Luis; Martínez-García, Antonio; Moreno, Ignacio

    2009-02-10

    In this work we describe the experimental realization of a simple scheme capable of implementing RGB improved dynamic color binary-phase Fourier computer-generated holograms (CGHs) by means of a single ferroelectric liquid crystal on silicon (FLCOS) display and an electronically controlled color-filter wheel. Tricolor multiwavelength illumination is achieved by aligning an Ar-Kr laser (wavelengths lambda(B)=488 nm and lambda(G)=568 nm) and a He-Ne laser ((R)=633 nm). Chromatic compensation is achieved by synchronizing a time sequence of properly scaled CGHs displayed on the FLCOS display with the corresponding filter from the color wheel. Quality CGHs are designed for each color component by using an optimized iterative Fourier transform algorithm applied to a phase-only modulation display. As a result, we present excellent experimental results on the reconstruction of these time-multiplexed wavelength-compensated diffractive optical elements and color CGHs.

  13. Ferroelectric Tungsten Bronze Bulk Crystals and Epitaxial Thin Films for Electro-Optic Device Applications

    DTIC Science & Technology

    1984-02-01

    110) film orientations. Electro - optic measurements on SBN:60 single crystals have shown a high value for r51 of 80 x 10 to the minus 12th power m/v...showing morphotropic boundary conditions with enhanced dielectric properties. Both systems look promising for future electro - optic development.

  14. Molecular ferroelectrics: where electronics meet biology

    PubMed Central

    Li, Jiangyu; Liu, Yuanming; Zhang, Yanhang; Cai, Hong-Ling; Xiong, Ren-Gen

    2013-01-01

    In the last several years, we have witnessed significant advances in molecular ferroelectrics, with ferroelectric properties of molecular crystals approaching those of barium titanate. In addition, ferroelectricity has been observed in biological systems, filling an important missing link in bioelectric phenomena. In this perspective, we will present short historical notes on ferroelectrics, followed by overview on the fundamentals of ferroelectricity. Latest development in molecular ferroelectrics and biological ferroelectricity will then be highlighted, and their implications and potential applications will be discussed. We close by noting molecular ferroelectric as an exciting frontier between electronics and biology, and a number of challenges ahead are also noted. PMID:24018952

  15. Molecular ferroelectrics: where electronics meet biology.

    PubMed

    Li, Jiangyu; Liu, Yuanming; Zhang, Yanhang; Cai, Hong-Ling; Xiong, Ren-Gen

    2013-12-28

    In the last several years, we have witnessed significant advances in molecular ferroelectrics, with the ferroelectric properties of molecular crystals approaching those of barium titanate. In addition, ferroelectricity has been observed in biological systems, filling an important missing link in bioelectric phenomena. In this perspective, we will present short historical notes on ferroelectrics, followed by an overview of the fundamentals of ferroelectricity. The latest developments in molecular ferroelectrics and biological ferroelectricity will then be highlighted, and their implications and potential applications will be discussed. We close by noting molecular ferroelectric as an exciting frontier between electronics and biology, and a number of challenges ahead are also described.

  16. Photoswitching of ferroelectric liquid crystals using chiral thioindigo dopants: The development of a photochemical switch hitter.

    PubMed

    Lemieux, Robert P

    2004-01-01

    By virtue of its spontaneous polarization (PS), a ferroelectric SmC* liquid crystal can be switched between two states corresponding to opposite molecular tilt orientations using an electric field, thus producing an ON-OFF light shutter between crossed polarizers. Considerable efforts have been made over the past decade to develop photonic FLC light shutters because of their potential uses in dynamic holography and optical data storage. The ON-OFF switching of a FLC light shutter can be triggered by light via a photoinversion of PS using a photochromic dopant. The spontaneous polarization is a chiral bulk property that can be left-handed (negative) or right-handed (positive), depending on the absolute configuration of the chiral component of the SmC* phase. In the approach described herein, the magnitude of PS is modulated via the photoisomerization of a chiral thioindigo dopant that undergoes a large increase in transverse dipole moment upon trans-cis photoisomerization. The sign of PS is photoinverted using an "ambidextrous" thioindigo dopant containing a chiral 2-octyloxy side chain that is coupled to the thioindigo core and induces a positive PS, and a chiral 2,3-difluorooctyloxy side chain that is decoupled from the core and induces a negative PS. In the trans form, the 2,3-difluorooctyloxy side chain predominates and the net PS induced by the dopant is negative. However, upon trans-cis-photoisomerization, the increase in transverse dipole moment of the 2-octyloxy/thioindigo unit raises its induced PS over that of the decoupled 2,3-difluorooctyloxy side chain, and thus inverts the net sign of PS induced by the dopant from negative to positive.

  17. Growth and Preparation of Lead-Potassium-Niobate (PKN) Single Crystals Specimens.

    DTIC Science & Technology

    1982-12-01

    POTASSIUM - NIOBATE (PKN) SINGLE CRYSTAL S SPECIMENS ,, Texas A&M University....... ’DTIC ELECTE MAR?7 1M8 R. K. Pandey B APPROVED FOR PUBLIC RELEASE...and Subtitle) S. TYPE Of REPORT II PERIOD COVERED Final Technical Report GROWTH AND PREPARATION OF LEAD- POTASSIUM -Ap80-Sp1 NIOBATE (PKN) SINGLE...Ba, Pb, Sr, Ca, Na, K etc. and B = Nb or Ta. Lead- potassium - niobate (PKN), Pb2KNb5015, is one of the members of the family of TB- ferroelectrics

  18. Quantitative lateral and vertical piezoresponse force microscopy on a PbTiO3 single crystal

    NASA Astrophysics Data System (ADS)

    Lei, Shiming; Koo, Tae-Yeong; Cao, Wenwu; Eliseev, Eugene A.; Morozovska, Anna N.; Cheong, S.-W.; Gopalan, Venkatraman

    2016-09-01

    Piezoresponse force microscopy (PFM) has emerged as a powerful tool for research in ferroelectric and piezoelectric materials. While the vertical PFM (VPFM) mode is well understood and applied at a quantitative level, the lateral PFM (LPFM) mode is rarely quantified, mainly due to the lack of a practical calibration methodology. Here by PFM imaging on a LiNbO3 180° domain wall, we demonstrate a convenient way to achieve simultaneous VPFM and LPFM calibrations. Using these calibrations, we perform a full quantitative VPFM and LPFM measurement on a (001)-cut PbTiO3 single crystal. The measured effective piezoelectric coefficients d33 e f f and d35 e f f together naturally provide more information on a material's local tensorial electromechanical properties. The proposed approach can be applied to a wide variety of ferroelectric and piezoelectric systems.

  19. Spray printing of organic semiconducting single crystals

    PubMed Central

    Rigas, Grigorios-Panagiotis; Payne, Marcia M.; Anthony, John E.; Horton, Peter N.; Castro, Fernando A.; Shkunov, Maxim

    2016-01-01

    Single-crystal semiconductors have been at the forefront of scientific interest for more than 70 years, serving as the backbone of electronic devices. Inorganic single crystals are typically grown from a melt using time-consuming and energy-intensive processes. Organic semiconductor single crystals, however, can be grown using solution-based methods at room temperature in air, opening up the possibility of large-scale production of inexpensive electronics targeting applications ranging from field-effect transistors and light-emitting diodes to medical X-ray detectors. Here we demonstrate a low-cost, scalable spray-printing process to fabricate high-quality organic single crystals, based on various semiconducting small molecules on virtually any substrate by combining the advantages of antisolvent crystallization and solution shearing. The crystals' size, shape and orientation are controlled by the sheer force generated by the spray droplets' impact onto the antisolvent's surface. This method demonstrates the feasibility of a spray-on single-crystal organic electronics. PMID:27874001

  20. Spray printing of organic semiconducting single crystals

    NASA Astrophysics Data System (ADS)

    Rigas, Grigorios-Panagiotis; Payne, Marcia M.; Anthony, John E.; Horton, Peter N.; Castro, Fernando A.; Shkunov, Maxim

    2016-11-01

    Single-crystal semiconductors have been at the forefront of scientific interest for more than 70 years, serving as the backbone of electronic devices. Inorganic single crystals are typically grown from a melt using time-consuming and energy-intensive processes. Organic semiconductor single crystals, however, can be grown using solution-based methods at room temperature in air, opening up the possibility of large-scale production of inexpensive electronics targeting applications ranging from field-effect transistors and light-emitting diodes to medical X-ray detectors. Here we demonstrate a low-cost, scalable spray-printing process to fabricate high-quality organic single crystals, based on various semiconducting small molecules on virtually any substrate by combining the advantages of antisolvent crystallization and solution shearing. The crystals' size, shape and orientation are controlled by the sheer force generated by the spray droplets' impact onto the antisolvent's surface. This method demonstrates the feasibility of a spray-on single-crystal organic electronics.

  1. Liquid crystal deposition on poled, single crystalline lithium niobate

    NASA Astrophysics Data System (ADS)

    Bharath, S. C.; Pimputkar, K. R.; Pronschinske, A. M.; Pearl, T. P.

    2008-01-01

    For the purpose of elucidating the mechanisms for molecular organization at poled ferroelectric surfaces, single crystalline lithium niobate (LN), 'Z-cut' along the (0 0 0 1) plane, has been prepared and characterized and subsequently exposed to liquid crystal molecules. As a model system we chose to study the anchoring of 4- n-octyl-4'-cyanobiphenyl (8CB) to LN. Liquid crystalline films are of interest because of their useful electronic and optical properties as well as chemical sensing attributes. Low-energy electron diffraction (LEED), atomic force microscopy (AFM), surface contact angle measurements (CA), and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface of lithium niobate as well as the nature of 8CB films grown on the surface. Atomically flat LN surfaces were prepared as a support for monolayer thick, 8CB molecular domains. 8CB liquid crystal molecules were deposited by an ambient vaporization technique and the films were analyzed using XPS and CA. Understanding electrostatic anchoring mechanisms and thin film organization for this molecule on uniformly poled surfaces allows for a fuller appreciation of how molecular deposition of other polarizable molecules on periodically poled and patterned poled lithium niobate surfaces would occur.

  2. Domains in Ferroelectric Nanostructures

    NASA Astrophysics Data System (ADS)

    Gregg, Marty

    2010-03-01

    , the need to fully understand how size and morphology affect domain behaviour in small scale ferroelectrics is obvious. In this talk, observations from a programme of study examining domains in meso and nano-scale BaTiO3 shapes, that have been cut directly from bulk single crystal using focused ion beam milling, will be presented. In general, the equilibrium static domain configurations that occur appear to be the result of a simultaneous desire to minimize both the macroscopic strain and depolarizing fields developed on cooling through the Curie Temperature. While such governing factors might be obvious, the specific patterns that result as a function of morphology are often non-intuitive, and a series of images of domains in nanodots, rods and wires will be presented and rationalised. In addition, the nature in which morphological factors influence domain dynamics during switching will be discussed, with particular focus on axial switching in nanowires, and the manner in which local surface perturbations (such as notches and antinotches) affect domain wall propagation. In collaboration with Alina Schilling, Li-Wu Chang, Mark McMillen, Raymond McQuaid, and Leo McGilly, Queen's University Belfast; Gustau Catalan, Universitat Autonoma de Barcelona; and James Scott, University of Cambridge.

  3. Field induced phase transitions and energy harvesting performance of (Pb,La)(Zr,Sn,Ti)O3 single crystal

    NASA Astrophysics Data System (ADS)

    Zhuo, Fangping; Li, Qiang; Li, Yuanyuan; Gao, Jinghan; Yan, Qingfeng; Zhang, Yiling; Xi, Xiaoqing; Chu, Xiangcheng; Cao, Wenwu

    2017-02-01

    (Pb,La)(Zr,Sn,Ti)O3 (PLZST) single crystals with composition close to the morphotropic phase boundary had been grown by the flux method. The antiferroelectric-ferroelectric phase switching electric field was 0.8 kV/mm. Temperature-dependent dielectric and polarization versus electric field hysteresis loops revealed that the electric field induced ferroelectric phase could transform back into the antiferroelectric phase at depolarization temperature (145 °C). An enhanced pyroelectric coefficient value of 1.46 μC/cm2/K was obtained at 145 °C, which is several times larger than that of conventional pyroelectric materials. Furthermore, multiple peak pyroelectric responses and an enhanced harvested energy density value of 0.4 J/cm3 were achieved in the PLZST crystal. The enhanced harvested energy density and multiple peak pyroelectric responses make the PLZST crystal a promising candidate for high sensitive temperature sensors and energy conversion technologies.

  4. Kinetics of nucleation of thermodynamically ordered ferroelectric phases in PbMg1/3Nb2/3O3- xPbTiO3 crystals with different compositions

    NASA Astrophysics Data System (ADS)

    Kamzina, L. S.

    2016-12-01

    The kinetics of electric field-induced nucleation of ordered ferroelectric phases from a mixed glassy relaxor state has been studied in a number of single-crystal (1- x)PbMg1/3Nb2/3O3- xPbTiO3 (PMN- xPT) solid solutions ( x = 29, 33, 35%) lying in a morphotropic phase region. It is shown that the formation of these phases and fast establishment of a macroscopic polarization are preceded by some delay time, depending on the electric field strength and temperature. It is found that the monoclinic phase is thermodynamically stable at room temperature in all the compounds in the time ( 3000 s) and electric field ( 1 kV/cm) ranges under study, whereas the monoclinic phase of the compound with x = 35% transforms, at temperatures near the temperature of the morphotropic phase transition after insignificant time interval of 100 s, to another stable ferroelectric tetragonal phase.

  5. Single Crystals Grown Under Unconstrained Conditions

    NASA Astrophysics Data System (ADS)

    Sunagawa, Ichiro

    Based on detailed investigations on morphology (evolution and variation in external forms), surface microtopography of crystal faces (spirals and etch figures), internal morphology (growth sectors, growth banding and associated impurity partitioning) and perfection (dislocations and other lattice defects) in single crystals, we can deduce how and by what mechanism the crystal grew and experienced fluctuation in growth parameters through its growth and post-growth history under unconstrained condition. The information is useful not only in finding appropriate way to growing highly perfect and homogeneous single crystals, but also in deciphering letters sent from the depth of the Earth and the Space. It is also useful in discriminating synthetic from natural gemstones. In this chapter, available methods to obtain molecular information are briefly summarized, and actual examples to demonstrate the importance of this type of investigations are selected from both natural minerals (diamond, quartz, hematite, corundum, beryl, phlogopite) and synthetic crystals (SiC, diamond, corundum, beryl).

  6. High-pressure Raman study of two ferroelectric crystals closely related to PbTiO3

    NASA Astrophysics Data System (ADS)

    Burns, Gerald; Sanjurjo, J. A.; López-Cruz, E.

    1984-12-01

    We report high-pressure Raman measurements of the zone-center phonons in two ferroelectric crystals that closely resemble the ABO3 perovskite crystal PbTiO3. These crystals are (Pb0.22Ba0.78)TiO3, i.e., Ba replacing Pb on the A site, and Pb(Ti0.81Sn0.19)O3, i.e., Sn replacing Ti on the B site. In both cases, at room temperature, we follow the modes and determine Pc, the transition pressure from the ferroelectric tetragonal phase to the cubic phase, to be 4.3 and 9.0 GPa, respectively. By observing the coalescence to the same frequency of the appropriate high-energy A1(TO)+E(TO) pairs of phonons, we determine the second-order character of the phase transitions at Pc. The tendency towards a second-order phase transition seems to be the rule at Pc as long as one makes the measurements at a temperature well below Tc; this is in agreement with theory. Thus, these systems exhibit tricritical points in the (P,T) phase diagram. The soft-E(TO)-phonon frequency (ω0) and damping constant (γ) can be measured to pressures reasonably close to Pc while the mode remains underdamped. These results are discussed in terms of a frequency-independent damping constant for the behavior of ω0 and γ near Pc. In the (Pb,Ba)TiO3 crystal, the hydrostatic pressure increases the intensity of the soft A1(TO) mode making it observable. This seems to happen in general in the perovskites. In the Pb(Ti,Sn)O3 crystal we observe the coupling of the soft E(TO) mode with an extra mode at 59 cm-1; this also has been studied as a function of temperature.

  7. Nanoscale probing and photonic applications of ferroelectric domain walls

    NASA Astrophysics Data System (ADS)

    Tian, Lili

    Ferroelectrics are a versatile solid-state platform for a new generation of micro- and nanophotonic applications. Conventional integrated optics has often treated the phenomenon of ferroelectric domains and domain walls more as a nuisance rather than an asset. Ironically, domain walls can be immensely valuable in realizing a wide variety of new functionalities such as laser scanning, dynamic focusing, frequency conversion, beam shaping, waveguiding, high-speed modulation, and photonic crystal structures. All of these functions can be realized by shaping ferroelectric domain walls into arbitrary shapes on micro to nanoscale dimensions. Domain walls, however, have a mind of their own when it comes to shaping them. This thesis will focus on the fundamental domain switching characteristics under the uniform electrical fields, and local electromechanical response across the single ferroelectric domain wall in ferroelectric crystals lithium niobate, lithium tantalate and strontium barium niobate. The local electromechanical response across the single was modeled using finite element method to better understand the fundamentals of piezoelectric force microscopy in order to quantitatively interpret the measured material properties. The influence of stoichiometry on domain dynamics on macroscale and on local electromechanical properties on nanoscale was studied. The challenges in shaping ferroelectric domain are discussed and the examples of optical devices such as optical switch and optical beam deflector based on ferroelectric domain walls are presented.

  8. Fatigue hardening in niobium single crystals.

    NASA Technical Reports Server (NTRS)

    Doner, M.; Diprimio, J. C.; Salkovitz, E. I.

    1973-01-01

    Nb single crystals of various orientations were cyclically deformed in tension-compression under strain control. At low strain amplitudes all crystals oriented for single slip and some oriented for multiple slip showed a two stage hardening. When present, the first stage was characterized with almost no cyclic work hardening. The rate of hardening in the second stage increased with strain amplitude and the amount of secondary slip. In crystals oriented for single slip kink bands developed on their side faces during rapid hardening stage which resulted in considerable amount of asterism in Laue spots. A cyclic stress-strain curve independent of prior history was found to exist which was also independent of crystal orientation. Furthermore, this curve differed only slightly from that of polycrystalline Nb obtained from data in literature.

  9. Dielectric, electro-optical, and photoluminescence characteristics of ferroelectric liquid crystals on a graphene-coated indium tin oxide substrate.

    PubMed

    Singh, Dharmendra Pratap; Gupta, Swadesh Kumar; Vimal, Tripti; Manohar, Rajiv

    2014-08-01

    Multilayer graphene was deposited on indium tin oxide (ITO) -coated glass plates and characterized by suitable techniques. A liquid crystal sample cell was designed using graphene deposited ITO glass plates without any additional treatment for alignment. Ferroelectric liquid crystal (FLC) material was filled in the sample cell. The effect of multilayer graphene on the characteristics of FLC material was investigated. The extremely high relative permittivity of pristine graphene and charge transfer between graphene and FLC material were consequences of the enormous increase in relative permittivity for the graphene-FLC (GFLC) system as compared to pure FLC. The presence of multilayer graphene suppresses the ionic impurities, comprised in the FLC material at lower frequencies. The ionic charge annihilation mechanism might be responsible for the reduction of ionic impurities. The presence of graphene reduces the net ferroelectricity and results in a change in the spontaneous polarization of pure FLC. Rotational viscosity of the GFLC system also decreases due to the strong π-π interaction between the FLC molecule and multilayer graphene. The photoluminescence of the GFLC system is blueshifted as compared to pure FLC, which is due to the coupling of energy released in the process of charge annihilation and photon emission.

  10. Characterization of zinc selenide single crystals

    NASA Technical Reports Server (NTRS)

    Gerhardt, Rosario A.

    1996-01-01

    ZnSe single crystals of high quality and low impurity levels are desired for use as substrates in optoelectronic devices. This is especially true when the device requires the formation of homoepitaxial layers. While ZnSe is commercially available, it is at present extremely expensive due to the difficulty of growing single crystal boules with low impurity content and the resultant low yields. Many researchers have found it necessary to heat treat the crystals in liquid Zn in order to remove the impurities, lower the resistivity and activate the photoluminescence at room temperature. The physical vapor transport method (PVT) has been successfully used at MSFC to grow many single crystals of II-VI semiconducting materials including ZnSe. The main goal at NASA has been to try to establish the effect of gravity on the growth parameters. To this effect, crystals have been grown vertically upwards or horizontally. Both (111) and (110) oriented ZnSe crystals have been obtained via unseeded PVT growth. Preliminary characterization of the horizontally grown crystals has revealed that Cu is a major impurity and that the low temperature photoluminescence spectra is dominated by the copper peak. The ratio of the copper peak to the free exciton peak is being used to determine variations in composition throughout the crystal. It was the intent of this project to map the copper composition of various crystals via photoluminescence first, then measure their electrical resistivity and capacitance as a function of frequency before proceeding with a heat treatment designed to remove the copper impurities. However, equipment difficulties with the photoluminescence set up, having to establish a procedure for measuring the electrical properties of the as-grown crystals and time limitations made us re-evaluate the project goals. Vertically grown samples designated as ZnSe-25 were chosen to be measured electrically since they were not expected to show as much variation in their

  11. Effect of boundary surfaces on the effective dielectric susceptibility of the helical structure of a ferroelectric liquid crystal

    SciTech Connect

    Kaznacheev, A. V.; Pozhidaev, E. P.

    2015-08-15

    We present the results of a theoretical investigation of the effect of boundary surfaces of a liquidcrystal cell on the effective dielectric susceptibility of the helical structure of a ferroelectric smectic C* liquid crystal (FLC). We consider for this purpose the deformation and untwisting of the helix by solid surfaces bounding the FLC layer. An analytic expression is obtained for critical thickness d{sub c} of the liquid-crystal layer, for which untwisting of the helix by surfaces takes place. In calculating the effective dielectric susceptibility, it is shown that the deformation of the FLC helix by the boundaries leads to the occurrence of anisotropy in the effective dielectric susceptibility in the plane perpendicular to the helix axis.

  12. Effects of nanoparticle doping on the phase transitional behaviour of ferroelectric liquid crystal Langmuir-Blodgett composite films

    NASA Astrophysics Data System (ADS)

    Kaur, Ramneek; Raina, K. K.

    2015-12-01

    Langmuir-Blodgett films of ferroelectric liquid crystals (FLCs) doped with a low concentration of functionalized Al: ZnO (AZO) nanoparticles were prepared and characterized. Pressure-area isotherms show that the nanoparticles as well as FLC composite systems have the capability to form stable monolayers at the air-water interface. The molecular interaction between nanoparticles and FLC molecules increased during barrier compression, which resulted in increased surface pressure. We observed various phases in isotherms with increasing concentration of nanoparticles in the FLC matrix. An X-ray diffraction profile at a low angle confirmed that FLCs retain their layer structure at a low concentration doping of AZO nanoparticles in the FLC matrix. Atomic force microscopy images indicate that low wt% composites are uniformly deposited without disturbing the translation behaviour of SmC* liquid crystals.

  13. Performance of Single Crystal Niobium Cavities

    SciTech Connect

    Kneisel, Peter; Ciovati, Gianluigi; Singer, Waldemar; Singer, Xenia; Reschke, Detlef; Brinkmann, A.

    2008-07-01

    We have fabricated and tested a total of six single cell niobium cavities, made from single crystal, high purity niobium. Two of the three cavities of the TESLA shape (1300 MHz) were made from Heraeus niobium by extending a smaller single crystal by rolling and annealing steps; the third cavity was made by spinning from CBMM material. The three other cavities of the scaled "Low Loss" (LL) shape (two) and "High Gradient" (HG) shape (one) resonated at 2.3 GHz and were fabricated from "as received" single crystals, both from Heraeus and CBMM niobium. After appropriate surface treatments by buffered chemical polishing and electropolishing most cavities performed quite nicely and peak surface magnetic fields of ~ 160 mT or above corresponding to accelerating gradients between 38 MV/m and 45 MV/m were reached. This paper reports about the performance of these cavities.

  14. INVESTIGATION OF A COMPOUND REPORTED AS BOTH FERRIMAGNETIC AND FERROELECTRIC,

    DTIC Science & Technology

    FERRITES , *FERROELECTRIC CRYSTALS, MAGNETIC PROPERTIES, X RAY DIFFRACTION, IMPURITIES, FERROELECTRICITY, FERROMAGNETISM, CRYSTAL STRUCTURE...DIELECTRIC PROPERTIES, MICROSCOPY, BARIUM COMPOUNDS, SAMARIUM COMPOUNDS, NIOBIUM COMPOUNDS, TITANIUM COMPOUNDS, TITANATES, PHOTOMICROGRAPHY, CRYSTAL LATTICES, OXIDES.

  15. Neutron detection with single crystal organic scintillators

    SciTech Connect

    Zaitseva, N; Newby, J; Hamel, S; Carman, L; Faust, M; Lordi, V; Cherepy, N; Stoeffl, W; Payne, S

    2009-07-15

    Detection of high-energy neutrons in the presence of gamma radiation background utilizes pulse-shape discrimination (PSD) phenomena in organics studied previously only with limited number of materials, mostly liquid scintillators and single crystal stilbene. The current paper presents the results obtained with broader varieties of luminescent organic single crystals. The studies involve experimental tools of crystal growth and material characterization in combination with the advanced computer modeling, with the final goal of better understanding the relevance between the nature of the organic materials and their PSD properties. Special consideration is given to the factors that may diminish or even completely obscure the PSD properties in scintillating crystals. Among such factors are molecular and crystallographic structures that determine exchange coupling and exciton mobility in organic materials and the impurity effect discussed on the examples of trans-stilbene, bibenzyl, 9,10-diphenylanthracene and diphenylacetylene.

  16. Oxygen Incorporation in Rubrene Single Crystals

    PubMed Central

    Mastrogiovanni, Daniel D. T.; Mayer, Jeff; Wan, Alan S.; Vishnyakov, Aleksey; Neimark, Alexander V.; Podzorov, Vitaly; Feldman, Leonard C.; Garfunkel, Eric

    2014-01-01

    Single crystal rubrene is a model organic electronic material showing high carrier mobility and long exciton lifetime. These properties are detrimentally affected when rubrene is exposed to intense light under ambient conditions for prolonged periods of time, possibly due to oxygen up-take. Using photoelectron, scanning probe and ion-based methods, combined with an isotopic oxygen exposure, we present direct evidence of the light-induced reaction of molecular oxygen with single crystal rubrene. Without a significant exposure to light, there is no reaction of oxygen with rubrene for periods of greater than a year; the crystal's surface (and bulk) morphology and chemical composition remain essentially oxygen-free. Grand canonical Monte Carlo computations show no sorbtion of gases into the bulk of rubrene crystal. A mechanism for photo-induced oxygen inclusion is proposed. PMID:24786311

  17. Infrared phonon dynamics of a multiferroic BiFeO3 single crystal

    NASA Astrophysics Data System (ADS)

    Lobo, R. P. S. M.; Moreira, R. L.; Lebeugle, D.; Colson, D.

    2007-11-01

    We discuss the infrared reflectivity measurement on a BiFeO3 single crystal between 5K and room temperature. The nine predicted ab -plane E phonon modes are fully and unambiguously determined. The frequencies of the four A1 c -axis phonons are found. These results settle issues between theory and data on ceramics. Our findings show that the softening of the lowest frequency E mode is responsible for the temperature dependence of the dielectric constant, indicating that the ferroelectric transition in BiFeO3 is soft-mode driven.

  18. Intelligent Processing of Ferroelectric Thin Films

    DTIC Science & Technology

    1994-05-31

    Review," Ferroelectrics, 75, 25(1987) be determined by the compensator. With the PLZT phase modulator, the above (3] H. Higashino , T. Kawaguchi, H...Phys. Lett. 42(1983)867 4. F. Wang and G. Haertling, Appl. Phys. Lett. 63(1993)1730 5. H. Higashino et al, Japan. J. Appi. Phys. Vol. 24(1985...Single Crystals," Phza.JRev. 97, 414(1991) 1585(1965) (2] D. Bonsurant and F. Gnadinger, "Ferroelectrics for [10] H. Higashino , T. Kawaguchi, H. Adachi, T

  19. Single crystals of metal solid solutions

    NASA Technical Reports Server (NTRS)

    Miller, J. F.; Austin, A. E.; Richard, N.; Griesenauer, N. M.; Moak, D. P.; Mehrabian, M. R.; Gelles, S. H.

    1974-01-01

    The following definitions were sought in the research on single crystals of metal solid solutions: (1) the influence of convection and/or gravity present during crystallization on the substructure of a metal solid solution; (2) the influence of a magnetic field applied during crystallization on the substructure of a metal solid solution; and (3) requirements for a space flight experiment to verify the results. Growth conditions for the selected silver-zinc alloy system are described, along with pertinent technical and experimental details of the project.

  20. Bioperformance of shape memory alloy single crystals.

    PubMed

    Yahia, L'h; Manceur, A; Chaffraix, P

    2006-01-01

    Shape memory alloys (SMA) represent a large family of alloys that show unique characteristics. They have been exploited in several fields for diverse applications. For the last 20 years, these alloys and more particularly Ni-Ti alloys have revolutionized the field of metallic biomaterials. Applications in the biomedical area are multiple and these materials improve significantly the quality of the diagnostics, treatments and surgeries. To our knowledge, most devices are made of SMAs in the polycrystalline form. Nevertheless, the single crystal form shows several promising advantages especially concerning its mechanical performances. In this paper we describe the advantages, advances and limits of using different SMA single crystals for biomedical applications, including biocompatibility and corrosion resistance. We also discuss the low response time of classical thermal SMAs as well as the new advances in research on magnetic SMA single crystals.

  1. Magnetoelasticity of Fe-Si single crystals

    SciTech Connect

    Xing, Q; Wu, D.; Lograsso, T. A.

    2010-04-20

    The tetragonal magnetostriction constant, (3/2){lambda}{sub 100}, of Fe-Si single crystals was measured and was found to be structure dependent. Similar to that of Fe-Ge single crystals, (3/2){lambda}{sub 100} is positive in the single phase A2 regime, becomes negative in the single phase D0{sub 3} regime, and changes from positive to negative between the two regimes. Short-range order in the A2 regime decreases the magnetostriction prior to the onset of long range order. In the single phase regions of both A2 and D0{sub 3}, thermal history does not show any obvious effect on the magnetostriction, contrary to that found for Fe-Ga alloys. However, in the regions of phase mixture involving A2, B2, and D0{sub 3} phases, quenching pushes the change in magnetostriction from positive to negative to higher Si contents.

  2. Characterization of KHCO3 Single Crystals

    NASA Astrophysics Data System (ADS)

    Abouelhassan, S.; Salman, F.; Elmansy, M.; Sheha, E.

    Single crystals of KHCO3 were grown by the slow evaporation technique of an aqueous solution. Characterization of the sample was done using different techniques such as X-ray diffraction, infrared spectra (IR) and the differential scanning calorimeter (DSC) technique. The analysis of the X-ray diffraction pattern indicated that the sample was a single crystal. The results obtained by IR and DSC indicated the presence of phase transition. From the analysis of DSC, the activation energy of transition was carried out by two methods (Kissinger and Ozawa).

  3. Inkjet printing of single-crystal films

    NASA Astrophysics Data System (ADS)

    Minemawari, Hiromi; Yamada, Toshikazu; Matsui, Hiroyuki; Tsutsumi, Jun'ya; Haas, Simon; Chiba, Ryosuke; Kumai, Reiji; Hasegawa, Tatsuo

    2011-07-01

    The use of single crystals has been fundamental to the development of semiconductor microelectronics and solid-state science. Whether based on inorganic or organic materials, the devices that show the highest performance rely on single-crystal interfaces, with their nearly perfect translational symmetry and exceptionally high chemical purity. Attention has recently been focused on developing simple ways of producing electronic devices by means of printing technologies. `Printed electronics' is being explored for the manufacture of large-area and flexible electronic devices by the patterned application of functional inks containing soluble or dispersed semiconducting materials. However, because of the strong self-organizing tendency of the deposited materials, the production of semiconducting thin films of high crystallinity (indispensable for realizing high carrier mobility) may be incompatible with conventional printing processes. Here we develop a method that combines the technique of antisolvent crystallization with inkjet printing to produce organic semiconducting thin films of high crystallinity. Specifically, we show that mixing fine droplets of an antisolvent and a solution of an active semiconducting component within a confined area on an amorphous substrate can trigger the controlled formation of exceptionally uniform single-crystal or polycrystalline thin films that grow at the liquid-air interfaces. Using this approach, we have printed single crystals of the organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) (ref. 15), yielding thin-film transistors with average carrier mobilities as high as 16.4cm2V-1s-1. This printing technique constitutes a major step towards the use of high-performance single-crystal semiconductor devices for large-area and flexible electronics applications.

  4. Microhardness studies of sulfamic acid single crystal

    NASA Astrophysics Data System (ADS)

    Santhosh Kumar, A.; Joseph, Cyriac; Paulose, Reshmi; R, Rajesh; Joseph, Georgekutty; Louis, Godfrey

    2015-02-01

    Vicker's microhardness study of (100), (010) and (001) faces of a non-linear optical crystal sulfamic acid have been reported. Single crystals of sulfamic acid have been grown by slow evaporation method. The load dependence of the Vickers microhardness of sulfamic acid crystal were investigated and analyzed from the stand point of various theoretical models. Crystal samples in a, b and c-axes exhibit reverse indentation effect which is best described by Meyer's law, Hays-Kendall's approach and proportional specimen resistance (PSR) models. The negative values of load dependent quantities in Hays-Kendall's approach and PSR model suggest that the origin of indentation size effect is associated with the process of relaxation of indentation stresses.

  5. Magnetoelectric emission in rare-earth doped ferroelectric crystals La2Ti2O7:R3+ ( R=Er , Eu, and Nd)

    NASA Astrophysics Data System (ADS)

    Shimada, Y.; Kiyama, H.; Tokura, Y.

    2007-06-01

    The optical magnetoelectric (OME) effect, i.e., the change of optical response on the reversal of light propagation vector (k) , has been investigated for the emission of rare earth R3+ ion ( R=Nd , Eu, Er) doped in a ferroelectric La2Ti2O7 single crystal under magnetic field (H) . The symmetry condition for the appearance of the OME effect for H⊥k was confirmed by varying the relative angle between the electric polarization and magnetic field. Another tensor component of the second-order magnetolectric tensor βijk for H∥k , i.e., the magnetochiral effect, is allowed in the Faraday configuration but found to be small compared with the OME effect in the Voigt configuration. The importance of the spin-orbit coupling, the magnetic dipole transition, and the noncentrosymmetric crystal structure is discussed as the origin of the OME effect on the basis of the observed signal magnitude depending on the species of the rare-earth ion and its optical transition moment.

  6. Growth of single-crystal gallium nitride

    NASA Technical Reports Server (NTRS)

    Clough, R.; Richman, D.; Tietjen, J.

    1970-01-01

    Use of ultrahigh purity ammonia prevents oxygen contamination of GaN during growth, making it possible to grow the GaN at temperatures as high as 825 degrees C, at which point single crystal wafers are deposited on /0001/-oriented sapphire surfaces.

  7. A ferroelectric liquid crystal spatial light modulator encoded with orthogonal arrays and its optimized design for laser speckle reduction

    NASA Astrophysics Data System (ADS)

    Tong, Zhaomin; Chen, Xuyuan

    2017-03-01

    In laser projectors, speckle reduction can be achieved by projecting a changing binary phase diffuser onto the screen. Here, we sequentially encoded a commercialized ferroelectric liquid crystal spatial light modulator (FLC-SLM) with the rows of a two-level orthogonal array of order sixty-four, thus obtaining a changing binary phase diffuser. With the help of this binary phase diffuser, the subjective speckle contrast ratio on the screen is reduced from Cb=0.71 to Ca=0.1. Based on the experimental results, a simplified transparent FLC-SLM design is first proposed. This newly designed FLC-SLM has two phase modulation depths and can be driven with the passive matrix addressing scheme. Therefore, the control electronics of the proposed FLC-SLM can be significantly simplified compared to the currently used one.

  8. Copper oxide decorated multi-walled carbon nanotubes/ferroelectric liquid crystal composites for faster display devices

    NASA Astrophysics Data System (ADS)

    Malik, Anu; Prakash, Jai; Kumar, Anil; Dhar, Ajay; Biradar, Ashok M.

    2012-09-01

    We present faster display devices based on copper oxide decorated multi-walled carbon nanotubes (MWCNTs) doped ferroelectric liquid crystal (FLC) material. The fastening of the response has been attributed to decrease in rotational viscosity of the FLC material. The ionic impurities were also reduced by doping copper oxide decorated MWCNTs into the FLC material, and the reduction has been attributed to trapping of ions by the guest copper oxide decorated MWCNTs. The observations of fastening the response and reduction of ionic impurities have been verified by experimental data using dielectric and electro-optical studies. The underlying mechanism would certainly help to understand the basic mechanism of interaction of CNTs with FLC molecules and could be applied to fabricate ionic defects free faster display devices.

  9. Exfoliation of graphene oxide and its application in improving the electro-optical response of ferroelectric liquid crystal

    SciTech Connect

    Kumar, Veeresh; Kumar, Ajay; Bhandari, Shruti; Biradar, A. M.; Pasricha, Renu E-mail: renu1505@gmail.com; Reddy, G. B.

    2015-09-21

    Near complete exfoliation and reduction of lyophilized graphene oxide (GO) has been carried out at temperature as low as 400 °C. The structural characterizations of the reduced GO have been performed using X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy techniques. The morphological studies were carried out using scanning electron microscopy. The synthesized GO finds an application in improving the switching performance of a liquid crystal (LC) mixture by remarkably modifying the physical properties, such as spontaneous polarization and rotational viscosity of the ferroelectric LC (FLC) material which in turn resulted into faster response of the FLC. The present study explores the possibility of low temperature thermal reduction of GO along with its application in improving the properties of LC based display systems.

  10. Ferroelectric and electrical characterization of multiferroic BiFeO3 at the single nanoparticle level

    NASA Astrophysics Data System (ADS)

    Vasudevan, R. K.; Bogle, K. A.; Kumar, A.; Jesse, S.; Magaraggia, R.; Stamps, R.; Ogale, S. B.; Potdar, H. S.; Nagarajan, V.

    2011-12-01

    Ferroelectric BiFeO3 (BFO) nanoparticles deposited on epitaxial substrates of SrRuO3 (SRO) and La1-xSrxMnO3 (LSMO) were studied using band excitation piezoresponse spectroscopy (BEPS), piezoresponse force microscopy (PFM), and ferromagnetic resonance (FMR). BEPS confirms that the nanoparticles are ferroelectric in nature. Switching behavior of nanoparticle clusters were studied and showed evidence for inhomogeneous switching. The dimensionality of domains within nanoparticles was found to be fractal in nature, with a dimensionality constant of ˜1.4, on par with ferroelectric BFO thin-films under 100 nm in thickness. Ferromagnetic resonance studies indicate BFO nanoparticles only weakly affect the magnetic response of LSMO.

  11. A double-mode piezoelectric single-crystal ultrasonic micro-actuator.

    PubMed

    Guo, Mingsen; Dong, Shuxiang; Ren, Bo; Luo, Haosu

    2010-11-01

    Ternary Pb(In(1/2)Nb(1/2))O(3)-Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PIN-PMN-PT) single crystals with higher coercive field (E(C) ~9 kV/cm) and higher ferroelectric-transition temperature (T(R-T) = 108°C) were grown, and correspondingly, a double-mode piezoelectric ultrasonic micro-actuator made of PIN-PMN-PT crystal brick (5 x 1.5 x 1.32 mm) and operated in the first longitudinal and the second bending modes was developed. The ferroelectric, dielectric, electromechanical, and resonance displacement properties of the micro-actuator were characterized for miniature linear piezo-motor applications. The longitudinal displacement of the actuator is ~0.11 μm (with an applied voltage of 5 V), which is comparable to that of a multilayer piezoelectric-ceramic actuator of the same size. This crystal micro-actuator was successfully used to drive a slider moving linearly.

  12. MAGNETORESISTANCE AND HALL EFFECT IN SINGLE CRYSTALS OF ALUMINUM

    DTIC Science & Technology

    ALUMINUM, *SINGLE CRYSTALS, CRYSTALS, HALL EFFECT , IMPURITIES, LOW PRESSURE, MAGNETIC FIELDS, MAGNETIC PROPERTIES, PARTICLE TRAJECTORIES, ELECTRICAL RESISTANCE, SOLID STATE PHYSICS, SURFACE PROPERTIES.

  13. Growth and optimization of piezoelectric single crystal transducers for energy harvesting from acoustic sources

    NASA Astrophysics Data System (ADS)

    Dhar, Romit

    Low power requirements of modern sensors and electronics have led to the examination of the feasibility of several energy harvesting schemes. This thesis describes the fabrication and performance of an acoustic energy harvester with single crystal piezoelectric unimorph. The unimorphs were fabricated from single crystal relaxor ferroelectric (1-x)PMN - xPT grown with x = 0.3 and 0.32 as the starting composition. It is demonstrated that significant power can be harvested using unimorph structures from an acoustic field at resonance. Passive circuit components were used for output circuit with a resistive load in series with a tunable inductor. A tuning capacitor connected in parallel to the device further increased the power output by matching the impedance of the unimorph. The power harvested can be either used directly for running low-power devices or can be stored in a rechargeable battery. A comparison of the performance of PMN-PT and PZT unimorphs at the resonance of the coupled structure under identical excitation conditions was done. For a certain optimized thickness ratio and circuit parameters, the single crystal PMN-PT unimorph generated 30 mW of power while a PZT unimorph generated 7.5 mW at resonance and room temperature. The harvested output power from the single crystal PMN-PT unimorphs depends on several material properties, physical and ambient parameters and an effort has been made to study their effect on the performance. A self-seeding high pressure Bridgman (HPB) technique was used to grow the PMN-PT single crystal ingots in a cost-effective way in our laboratories. Several techniques of material processing were developed to fabricate the PMN-PT single crystal unimorphs from as grown bulk ingots. This growth technique produced good quality single crystals for our experiments, with a k33 = 0.91 for a <001> oriented bar.

  14. The interface between ferroelectric and 2D material for a Ferroelectric Field-Effect Transistor

    NASA Astrophysics Data System (ADS)

    Park, Nahee; Kang, Haeyong; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok

    We have studied electrical property of ferroelectric field-effect transistor which consists of graphene on hexagonal Boron-Nitride (h-BN) gated by a ferroelectric, PMN-PT (i.e. (1-x)Pb(Mg1/3Nb2/3) O3-xPbTiO3) single-crystal substrate. The PMN-PT was expected to have an effect on polarization field into the graphene channel and to induce a giant amount of surface charge. The hexagonal Boron-Nitride (h-BN) flake was directly exfoliated on the PMN-PT substrate for preventing graphene from directly contacting on the PMN-PT substrate. It can make us to observe the effect of the interface between ferroelectric and 2D material on the device operation. Monolayer graphene as 2D channel material, which was confirmed by Raman spectroscopy, was transferred on top of the hexagonal Boron-Nitride (h-BN) by using the conventional dry-transfer method. Here, we can demonstrate that the structure of graphene/hexagonal-BN/ferroelectric field-effect transistor makes us to clearly understand the device operation as well as the interface between ferroelectric and 2D materials by inserting h-BN between them. The phenomena such as anti-hysteresis, current saturation behavior, and hump-like increase of channel current, will be discussed by in terms of ferroelectric switching, polarization-assisted charge trapping.

  15. Dielectric, electromechanical, and elastic properties of Rb1- x (NH4) x H2PO4 single crystals

    NASA Astrophysics Data System (ADS)

    Korotkov, L. N.; Likhovaya, D. V.; Levitskii, R. R.; Zachek, I. R.

    2017-01-01

    The longitudinal dielectric, piezoelectric, and elastic characteristics of ferroelectric RbH2PO4 and antiferroelectric NH4H2PO4 crystals are calculated in terms of the modified model of proton ordering with allowance for the piezoelectric coupling in an approximation of a four-particle cluster. The results obtained agree well with known experimental data. Along with this, the electromechanical properties of a Rb0.2(NH4)0.8H2PO4 single crystal undergoing an antiferroelectric phase transition have been studied experimentally over a wide temperature range. The model predictions and the experimental data agree qualitatively.

  16. Curved Ferroelectric Liquid Crystal Matrix Displays Driven by Field-Sequential-Color and Active-Matrix Techniques

    NASA Astrophysics Data System (ADS)

    Fujikake, Hideo; Sato, Hiroto; Murashige, Takeshi; Fujisaki, Yoshihide; Kurita, Taiichiro; Furukawa, Tadahiro; Sato, Fumio

    This paper describes a curved field-sequential-color matrix display using fast-response ferroelectric liquid crystal. Black matrix and transparent electrode patterns were formed on a thin plastic substrate by a transfer method from a glass substrate. While a composite film of liquid crystal and micro-polymers of walls and fibers was formed between the flexible substrates by printing, laminating and curing processes of a solution of monomers and liquid crystal, the mechanical stability was enhanced by use of multi-functional monomers to form large display panels. The image pixels of the matrix panel were driven by an active matrix scheme using an external switch transistor array at a frequency of 180 Hz for intermittent three-primary-color backlight illumination. The flexible A4-paper-sized color display with 24 × 16 pixels and 60 Hz field frequency was demonstrated by illuminating it with sequential three-primary-color lights from light-emitting diodes of the backlight. Our display system is useful in various information displays because of its freedom of setting and location.

  17. Lightweight optical mirrors formed in single crystal substrate

    NASA Technical Reports Server (NTRS)

    Bly, Vincent T. (Inventor)

    2006-01-01

    This invention is directed to a process for manufacturing a lightweight mirror from a single crystal material, such as single crystal silicon. As a near perfect single crystal material, single crystal silicon has much lower internal stress than a conventional material. This means much less distortion of the optical surface during the light weighting process. After being ground and polished, a single crystal silicon mirror is light weighted by removing material from the back side using ultrasonic machining. After the light weighting process, the single crystal silicon mirror may be used as-is or further figured by conventional polishing or ion milling, depending on the application and the operating wavelength.

  18. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, Frank R.; Gillies, Donald C.; Watring, Dale A.

    1999-01-01

    The objective of the study is to establish the effects of processing semiconducting, solid solution, single crystals in a microgravity environment on the metallurgical, compositional, electrical, and optical characteristics of the crystals. The alloy system being investigated is the solid solution semiconductor Hg(1-x)Cd(x)Te, with x-values appropriate for infrared detector applications in the 8 to 14 mm wavelength region. Both melt and Te-solvent growth are being performed. The study consists of an extensive ground-based experimental and theoretical research effort followed by flight experimentation where appropriate. The ground-based portion of the investigation also includes the evaluation of the relative effectiveness of stabilizing techniques, such as applied magnetic fields, for suppressing convective flow during the melt growth of the crystals.

  19. Growth of lead magnesium niobate-lead titanate single crystals by seeded polycrystal conversion

    NASA Astrophysics Data System (ADS)

    Scotch, Adam Matthew

    Relaxor-based ferroelectric single crystals of Pb(Mg1/3Nb 2/3)O3-PbTiO3 [PMN-PT] have been produced via the Seeded Polycrystal Conversion [SPC] technique. Polycrystalline precursors of PMN-PT are converted to single crystals by inducing the boundary of a seed crystal to migrate through a polycrystalline matrix. The quality of PMN-PT single crystals grown by SPC is directly influenced by the microstructure of the polycrystalline precursor. The goal of this work was to examine the factors that controlled the final microstructure of the matrix and grown single crystals and to characterize their effects on properties. Sintering in oxygen was necessary to obtain fully dense matrix microstructures, which, in turn, produced pore-free single crystals. The primary role of oxygen was to remove insoluble gases before densification began, then to reduce the internal pressure by diffusing out and allowing the pores to close from pressures derived from their own curvatures. The presence of a PbO liquid phase assisted this process by enhancing the densification rate in the early stages of sintering. In contrast, fully-dense, hot-pressed samples of PMN-35PT with excess PbO underwent a de-densification process during the annealing treatments which was attributed to pore formation from internally evolved gases. Transparent single crystals with maximum strain values of 0.72% at 46 kV/cm, d33 ˜2180 pC/N, and a room temperature dielectric constant of ˜5300 were obtained for poled <001> oriented crystals of PMN-30mol.%PT. The dielectric behavior of {001} oriented single crystals was found to be highly dependent on the initial orientation of the seed crystal. For example, {111} seeded crystals grown in oxygen yielded Kmax values of ˜33000, while {001} seeded crystals grown in oxygen had Kmax values of ˜25000. In addition, the Tmax values were 3 to 5°C higher for crystals grown from {001} seeds, compared to {111} seeds.

  20. Novel HDD-type SNDM ferroelectric data storage system aimed at high-speed data transfer with single probe operation.

    PubMed

    Hiranaga, Yoshiomi; Uda, Tomoya; Kurihashi, Yuichi; Tanaka, Kenkou; Cho, Yasuo

    2007-12-01

    In this study, several read/write tests were conducted using a novel ferroelectric data storage test system equipped with a spindle motor, targeted at high-speed data transfer using a single probe head. A periodically inverted signal can be read out correctly with a bit rate of 100 kbps using this test system, and 10 Mbps data transfer is also possible during writing operations. The effect of a dc-offset voltage applied to the writing waveform with high-speed probe scanning is discussed. In addition, a novel noncontact probe height control technique was adopted to solve the problem of tip abrasion.

  1. Single-crystal gallium nitride nanotubes.

    PubMed

    Goldberger, Joshua; He, Rongrui; Zhang, Yanfeng; Lee, Sangkwon; Yan, Haoquan; Choi, Heon-Jin; Yang, Peidong

    2003-04-10

    Since the discovery of carbon nanotubes in 1991 (ref. 1), there have been significant research efforts to synthesize nanometre-scale tubular forms of various solids. The formation of tubular nanostructure generally requires a layered or anisotropic crystal structure. There are reports of nanotubes made from silica, alumina, silicon and metals that do not have a layered crystal structure; they are synthesized by using carbon nanotubes and porous membranes as templates, or by thin-film rolling. These nanotubes, however, are either amorphous, polycrystalline or exist only in ultrahigh vacuum. The growth of single-crystal semiconductor hollow nanotubes would be advantageous in potential nanoscale electronics, optoelectronics and biochemical-sensing applications. Here we report an 'epitaxial casting' approach for the synthesis of single-crystal GaN nanotubes with inner diameters of 30-200 nm and wall thicknesses of 5-50 nm. Hexagonal ZnO nanowires were used as templates for the epitaxial overgrowth of thin GaN layers in a chemical vapour deposition system. The ZnO nanowire templates were subsequently removed by thermal reduction and evaporation, resulting in ordered arrays of GaN nanotubes on the substrates. This templating process should be applicable to many other semiconductor systems.

  2. Macrodeformation Twins in Single-Crystal Aluminum

    NASA Astrophysics Data System (ADS)

    Zhao, F.; Wang, L.; Fan, D.; Bie, B. X.; Zhou, X. M.; Suo, T.; Li, Y. L.; Chen, M. W.; Liu, C. L.; Qi, M. L.; Zhu, M. H.; Luo, S. N.

    2016-02-01

    Deformation twinning in pure aluminum has been considered to be a unique property of nanostructured aluminum. A lingering mystery is whether deformation twinning occurs in coarse-grained or single-crystal aluminum at scales beyond nanotwins. Here, we present the first experimental demonstration of macrodeformation twins in single-crystal aluminum formed under an ultrahigh strain rate (˜106 s-1 ) and large shear strain (200%) via dynamic equal channel angular pressing. Large-scale molecular dynamics simulations suggest that the frustration of subsonic dislocation motion leads to transonic deformation twinning. Deformation twinning is rooted in the rate dependences of dislocation motion and twinning, which are coupled, complementary processes during severe plastic deformation under ultrahigh strain rates.

  3. Optimizing Scale Adhesion on Single Crystal Superalloys

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Pint, Bruce A.

    2000-01-01

    To improve scale adhesion, single crystal superalloys have been desulfurized to levels below 1 ppmw by hydrogen annealing. A transition to fully adherent behavior has been shown to occur at a sulfur level of about 0.2 ppmw, as demonstrated for PWA 1480, PWA 1484, and Rene N5 single crystal superalloys in 1100-1150 C cyclic oxidation tests up to 2000 h. Small additions of yttrium (15 ppmw) also have been effective in producing adhesion for sulfur contents of about 5 ppmw. Thus the critical Y/S ratio required for adhesion was on the order of 3-to-1 by weight (1-to-1 atomic), in agreement with values estimated from solubility products for yttrium sulfides. While hydrogen annealing greatly improved an undoped alloy, yielding <= 0.01 ppmw S, it also produced benefits for Y-doped alloys without measurably reducing the sulfur content.

  4. Stabilization of metastable ferroelectric Ba1−xCaxTi2O5 by breaking Ca-site selectivity via crystallization from glass

    PubMed Central

    Masuno, Atsunobu; Moriyoshi, Chikako; Mizoguchi, Teruyasu; Okajima, Toshihiro; Kuroiwa, Yoshihiro; Arai, Yasutomo; Yu, Jianding; Inoue, Hiroyuki; Watanabe, Yasuhiro

    2013-01-01

    The thermal stability and dielectric and structural properties of ferroelectric Ba1−xCaxTi2O5 (0 ≤ x ≤ 0.30) prepared by crystallization from glass are investigated. The Ba1−xCaxTi2O5 compounds with x < 0.10 are thermally stable phases, while those with x ≥ 0.10 are metastable phases. The ferroelectric transition temperature drastically decreases from 470 to 220°C with increasing x. Crystal structure analyses reveal that one of two possible Ba sites is occupied by Ca in the stable phase region, while Ca-site selectivity is broken in the metastable phase region. The Ca-site selectivity introduces local distortion and makes the crystal lattice unstable. However, the local distortion is suppressed by the occupancy of Ca into both Ba sites. Accordingly, the metastable ferroelectric phase can be obtained beyond the substitution limit of Ca by crystallization from the glassy state. The stabilization mechanism provides possible wide control of the functionality of materials by expanding the composition range. PMID:24145958

  5. THE FERROELECTRIC AND STRUCTURAL PROPERTIES OF HAFNIUM OXIDE COMPOUNDS,

    DTIC Science & Technology

    HAFNIUM COMPOUNDS, OXIDES), (* FERROELECTRICITY , HAFNIUM COMPOUNDS), (*CRYSTAL STRUCTURE, HAFNIUM COMPOUNDS), DIELECTRIC PROPERTIES, HYSTERESIS... FERROELECTRIC MATERIALS, SOLID SOLUTIONS, X RAY DIFFRACTION, CRYSTAL LATTICES, LOW TEMPERATURE, CALCIUM COMPOUNDS, STRONTIUM COMPOUNDS, LEAD COMPOUNDS, BARIUM COMPOUNDS

  6. Thermal properties of UO2 single crystal

    NASA Astrophysics Data System (ADS)

    Gofryk, K.; Du, S.; Andersson, A. D.; Stanek, C. R.; Schulze, R.; Safarik, D.; Mihaila, B.; Lashley, J. C.; Smith, J. L.

    2013-03-01

    For decades UO2 has been the most widely studied actinide oxide because of its technological importance as fuel material for nuclear reactors. Therefore there is a large interest in understanding its thermal, transport and thermodynamic properties. We present recent experimental results for the thermal conductivity and thermal expansion of high quality UO2 single crystal, obtained for different crystallographic directions, and compare with results of molecular dynamics simulations. We will discuss the implications of this study.

  7. Growth of single crystals under hydrothermal conditions

    NASA Astrophysics Data System (ADS)

    Popolitov, Vladislav Ivanovich; Litvin, Boris Nikolaevich

    The book summarizes the available theoretical, methodological, and experimental data on the hydrothermal growth of inorganic compounds, such as simple and complex oxides, sulfides, silicates, germanates, phosphates, niobates, and tantalates. Attention is given to the physicochemical, hydrodynamic, and kinetic characteristics of the growth of these compounds, as well as hydrothermal growth techniques and equipment. The discussion also covers the morphogenetic characteristics of hydrothermally grown single crystals, their principal physical properties, and X-ray diffraction and structural data.

  8. A creep mechanism for metal single crystals

    SciTech Connect

    Cuitino, A.M.

    1995-12-31

    In this paper we present a mechanism of creep for metal single crystals. This creep mechanism is consistent with the hardening mechanism in metals single crystals, i.e. forest hardening. Hardening in metals is mainly due to the resistance to the dislocation motion opposed by obstacles. In single crystals, obstacles are generated by dislocation segments crossing the glide plane (forest dislocations). When a dislocation is released from an obstacle, it moves until stopped at the following obstacle inducing plastic deformation. It has been proposed as a mechanisms of creep that obstacles can be overcome by dislocation climb. However, the kind of obstacles remains in planes parallel to the gliding plane. Thus, the dislocation segment after climb is still stopped at the same obstacle and unable to glide, unless, a second jog moving in the forest dislocation meets simultaneously with the jog in the gliding segment. In this case, the gliding segment can move by the height of the forest jog. The gliding area is proportional to this height and the distance between obstacles. We call this mechanism of glide by congruent climb. Creep rate depends on the jog density and jog velocity. For a well-annealed material the number of jogs is relatively low. As plastic deformation proceeds, new jogs are formed by mainly two mechanisms: dislocation intersection and double cross slip. For a crystal undergoing single slip, the cross-slip contribution dominates jog generation, since dislocation intersections are relatively rare due to the low forest dislocation density. The situation is reversed for multiple glide as a consequence of the rapid dislocation multiplication which takes place in the active slip systems, which results in a high rate of dislocation intersection. The number of cross slip events and dislocation intersections can be readily estimated by our dislocation model of plastic deformation. Jog velocity is determined based on vacancy diffusion along the dislocation core.

  9. Ionic diffusion in single crystals of vermiculite

    SciTech Connect

    Maraqah, H.R.

    1993-01-01

    Novel guest-host compounds, based on single crystal vermiculite, were synthesized by diffusive techniques through a new hydrogen vermiculite. Single crystals were chosen because of the ease of characterization. An investigation of the ion transport properties of these single crystals was done to determine the mechanism of conductivity including the predominant charge carrier. Measurements of the ionic conductivity using impedance spectroscopy and X-ray lattice parameters of the ion-exchanged samples strongly suggest that the native cations and not protons are the major current carriers. Single crystals of hydrogen vermiculite were synthesized at room temperature by ion exchange from sodium-vermiculite using 1 molar acetic acid for a one week. Subsequent ion exchange with other cations was found to be much enhanced. Thus transition metals were exchanged in about a week in contrast to the need of several months using previous methods. The ionic conductivity of hydrogen vermiculite was measured and shown to be much lower than that of many other monovalent cations in the same host lattice. Its enthalpy of motion is also much lower. These marked differences suggest that protonic species do not play a significant role in charge transport in these layered materials. These materials were characterized by x-ray powder diffraction, thermogravimetric analysis and acid-base titration. Hydrogen-vermiculite was found to react with organic bases, like methylamine, ethylamine, n-butylamine, n-hexylamine, n-octylamine, n-decylamine, aniline, acrylamide, methacrylaminde, urea, 1,10phenanthroline, and 1,1phenanthroline ferrous sulfate complex, to undergo ion exchange with metal cations like sodium, zinc, copper(II) ions and polymerization reactions could be performed in the galleries of the structure like pyrrole and aniline. Its behavior was compared with that of powdered montmorillonite.

  10. Flexible single-crystal silicon nanomembrane photonic crystal cavity.

    PubMed

    Xu, Xiaochuan; Subbaraman, Harish; Chakravarty, Swapnajit; Hosseini, Amir; Covey, John; Yu, Yalin; Kwong, David; Zhang, Yang; Lai, Wei-Cheng; Zou, Yi; Lu, Nanshu; Chen, Ray T

    2014-12-23

    Flexible inorganic electronic devices promise numerous applications, especially in fields that could not be covered satisfactorily by conventional rigid devices. Benefits on a similar scale are also foreseeable for silicon photonic components. However, the difficulty in transferring intricate silicon photonic devices has deterred widespread development. In this paper, we demonstrate a flexible single-crystal silicon nanomembrane photonic crystal microcavity through a bonding and substrate removal approach. The transferred cavity shows a quality factor of 2.2×10(4) and could be bent to a curvature of 5 mm radius without deteriorating the performance compared to its counterparts on rigid substrates. A thorough characterization of the device reveals that the resonant wavelength is a linear function of the bending-induced strain. The device also shows a curvature-independent sensitivity to the ambient index variation.

  11. Anisotropy of sapphire single crystal sputtering

    SciTech Connect

    Minnebaev, K. F.; Tolpin, K. A.; Yurasova, V. E.

    2015-08-15

    We have studied the spatial distribution of particles sputtered from the base (0001) plane of a sapphire single crystal with trigonal crystalline lattice (α-Al{sub 2}O{sub 3}) that can be considered a superposition of two hexagonal close packed (hcp) structures–the ideal sublattice of oxygen and a somewhat deformed sublattice of aluminum. It is established that the particles sputtered from the base plane of sapphire are predominantly deposited along the sides of an irregular hexagon with spots at its vertices. The patterns of spots have been also studied for sputtering of particles from the (0001) face of a zinc single crystal with the hcp lattice. The spots of sputtered Zn atoms are arranged at the vertices of concentric equilateral hexagons. In both cases, the observed anisotropy of sputtering is related to focused collisions (direct and assisted focusing) and the channeling process. The chemical composition of spots has been determined in various regions of sputtered sapphire deposition. The results are discussed in comparison to analogous earlier data for secondary ion emission from an α-Al{sub 2}O{sub 3} single crystal.

  12. Secondary particle emission from sapphire single crystal

    NASA Astrophysics Data System (ADS)

    Minnebaev, K. F.; Khvostov, V. V.; Zykova, E. Yu.; Tolpin, K. A.; Colligon, J. S.; Yurasova, V. E.

    2015-07-01

    Secondary ion emission from sapphire single crystal has been studied experimentally and by means of computer simulation. The particular oscillations of secondary ion energy spectra and two specific maxima of O+ and Al+ ions were observed under irradiation of (0001) sapphire face by 1 and 10 keV Ar+ ions. We have explained this by the interplay of the charge exchange processes between moving particles and solids. The existence of two maxima in energy spectra of O+ and Al+ secondary ions can be also connected with special features of single-crystal sputtering: the low-energy peak can be formed by random sputtering and the high-energy peak from focusing collisions. In addition some similarity was found between the positions of low-energy maximum in energy spectra of Al+ ions emitted from sapphire and the principal maxima of Al+ ions ejected from the aluminum single crystal. This indicates a possibility to explain the presence of low-energy maximum in energy spectra of secondary ions ejecting from sapphire by emission of Al+ ions from aluminum islands appearing in a number of cases on the sapphire surface due to preferential sputtering of oxygen. These different mechanisms of creating the energy spectra of ions emitted from sapphire should be taken in account.

  13. Single crystal diamond detector for radiotherapy

    NASA Astrophysics Data System (ADS)

    Schirru, F.; Kisielewicz, K.; Nowak, T.; Marczewska, B.

    2010-07-01

    The new generation of synthetic diamonds grown as a CVD single crystal on a high pressure high temperature substrate offers a wide range of applications. In particular, because of the near tissue equivalence and its small size (good spatial resolution), CVD single crystal diamond finds applicability in radiotherapy as a dosemeter of ionizing radiation. In this paper we report the electrical and dosimetric properties of a new diamond detector which was fabricated at IFJ based on a single crystal detector-grade CVD diamond provided with a novel contact metallization. Diamond properties were assessed at IFJ using a Theratron 680E therapeutic 60Co gamma rays unit and at COOK with 6 and 18 MV x-rays Varian Clinac CL2300 C/D accelerator. The new dosemeter showed high electric and dosimetric performances: low value of dark current, high current at the level of some nanoamperes during irradiation, very fast dynamic response with a rise time amounting to parts of a second, good stability and repeatability of the current and linearity of the detector signal at different dose and dose rate levels typically applied in radiotherapy. The results confirm the potential applicability of diamond material as a dosemeter for applications in radiotherapy.

  14. Strain-gradient-induced polarization in SrTiO3 single crystals.

    PubMed

    Zubko, P; Catalan, G; Buckley, A; Welche, P R L; Scott, J F

    2007-10-19

    Piezoelectricity is inherent only in noncentrosymmetric materials, but a piezoelectric response can also be obtained in centrosymmetric crystals if subjected to inhomogeneous deformation. This phenomenon, known as flexoelectricity, can significantly affect the functional properties of insulators, particularly thin films of high permittivity materials. We have measured strain-gradient-induced polarization in single crystals of paraelectric SrTiO3 as a function of temperature and orientation down to and below the 105 K phase transition. Estimates were obtained for all the components of the flexoelectric tensor, and calculations based on these indicate that local polarization around defects in SrTiO3 may exceed the largest ferroelectric polarizations. A sign reversal of the flexoelectric response detected below the phase transition suggests that the ferroelastic domain walls of SrTiO3 may be polar.

  15. Charge transport in single crystal organic semiconductors

    NASA Astrophysics Data System (ADS)

    Xie, Wei

    Organic electronics have engendered substantial interest in printable, flexible and large-area applications thanks to their low fabrication cost per unit area, chemical versatility and solution processability. Nevertheless, fundamental understanding of device physics and charge transport in organic semiconductors lag somewhat behind, partially due to ubiquitous defects and impurities in technologically useful organic thin films, formed either by vacuum deposition or solution process. In this context, single-crystalline organic semiconductors, or organic single crystals, have therefore provided the ideal system for transport studies. Organic single crystals are characterized by their high chemical purity and outstanding structural perfection, leading to significantly improved electrical properties compared with their thin-film counterparts. Importantly, the surfaces of the crystals are molecularly flat, an ideal condition for building field-effect transistors (FETs). Progress in organic single crystal FETs (SC-FETs) is tremendous during the past decade. Large mobilities ~ 1 - 10 cm2V-1s-1 have been achieved in several crystals, allowing a wide range of electrical, optical, mechanical, structural, and theoretical studies. Several challenges still remain, however, which are the motivation of this thesis. The first challenge is to delineate the crystal structure/electrical property relationship for development of high-performance organic semiconductors. This thesis demonstrates a full spectrum of studies spanning from chemical synthesis, single crystal structure determination, quantum-chemical calculation, SC-OFET fabrication, electrical measurement, photoelectron spectroscopy characterization and extensive device optimization in a series of new rubrene derivatives, motivated by the fact that rubrene is a benchmark semiconductor with record hole mobility ~ 20 cm2V-1s-1. With successful preservation of beneficial pi-stacking structures, these rubrene derivatives form

  16. Single Crystal Technology for Making RRR Niobium Sheet

    SciTech Connect

    Graham, Ronald A.

    2007-08-09

    This paper reviews methods used to produce metallic single crystals. Methods are assessed in terms of being able to use the technique to produce RRR niobium single crystals for RF superconducting accelerator cavities.

  17. A nanoporous two-dimensional polymer by single-crystal-to-single-crystal photopolymerization.

    PubMed

    Kissel, Patrick; Murray, Daniel J; Wulftange, William J; Catalano, Vincent J; King, Benjamin T

    2014-09-01

    In contrast to the wide number and variety of available synthetic routes to conventional linear polymers, the synthesis of two-dimensional polymers and unambiguous proof of their structure remains a challenge. Two-dimensional polymers-single-layered polymers that form a tiling network in exactly two dimensions-have potential for use in nanoporous membranes and other applications. Here, we report the preparation of a fluorinated hydrocarbon two-dimensional polymer that can be exfoliated into single sheets, and its characterization by high-resolution single-crystal X-ray diffraction analysis. The procedure involves three steps: preorganization in a lamellar crystal of a rigid monomer bearing three photoreactive arms, photopolymerization of the crystalline monomers by [4 + 4] cycloaddition, and isolation of individual two-dimensional polymer sheets. This polymer is a molecularly thin (~1 nm) material that combines precisely defined monodisperse pores of ~9 Å with a high pore density of 3.3 × 10(13) pores cm(-2). Atomic-resolution single-crystal X-ray structures of the monomer, an intermediate dimer and the final crystalline two-dimensional polymer were obtained and prove the single-crystal-to-single-crystal nature and molecular precision of the two-dimensional photopolymerization.

  18. Quantitative nonlinear dielectric microscopy of periodically polarized ferroelectric domains

    NASA Astrophysics Data System (ADS)

    Gao, Chen; Duewer, Fred; Lu, Yalin; Xiang, X.-D.

    1998-08-01

    A nonlinear dielectric scanning tip microwave near-field microscope capable of submicron quantitative imaging of nonlinear dielectric constant was developed. This nondestructive technique was used to image the nonlinear dielectric constant profiles of an yttrium-doped LiNbO3 single crystal with periodically polarized ferroelectric domains.

  19. Temperature-induced sign reversal of biaxiality observed by conoscopy in some ferroelectric Sm-C* liquid crystals

    NASA Astrophysics Data System (ADS)

    Song, Jang-Kun; Chandani, A. D. L.; Fukuda, Atsuo; Vij, J. K.; Kobayashi, Ichiro; Emelyanenko, A. V.

    2007-07-01

    We have studied various ferroelectric liquid crystals to find the average molecular direction of the shortest axis in the perfectly unwound state by using tilted conoscopic measurements. We find that there exist two types of temperature dependencies of the biaxiality. Some materials exhibit increasing biaxiality while others show decreasing biaxiality with increasing temperature. The former shows a temperature-induced sign reversal of biaxiality. Three different physical mechanisms are identified as responsible for the emergence of biaxiality: (i) anisotropic fluctuations of the long molecular axis, (ii) a biased rotation around the long axis, and (iii) the local field effect. By means of a simple theoretical investigation, we conclude that these two types of trends are due mainly to the opposite signs of the biaxial order parameter C , which represents the second mechanism: the biased rotation around the long axis. This means that the central phenyl planes of molecules belonging to materials having biaxiality that increases with temperature are oriented on the average parallel to the tilt plane (the shortest index of refraction axis normal to the tilt plane), and, on the contrary, in those of the others molecules are oriented perpendicular to the tilt plane (the shortest index of refraction axis lying in the tilt plane). Thus, the direction of the phenyl ring plane of the liquid crystal molecules determines the different temperature dependencies of the biaxiality. It is also shown that the phenomenon of sign reversal of the biaxiality is due to the competitive contributions of the first and second physical mechanisms.

  20. Ho:YAG Single Crystal Fiber: Fabrication and Optical Characterization

    DTIC Science & Technology

    2014-06-16

    optical characterization 0.5% Holmium (Ho) doped YAG single crystal fiber (SCF) was fabricated using Laser Heated Pedestal Growth (LHPG) method and...ABSTRACT Ho:YAG single crystal fiber: fabrication and optical characterization Report Title 0.5% Holmium (Ho) doped YAG single crystal fiber (SCF) was...0.5% Holmium (Ho) doped YAG single crystal fiber (SCF) was fabricated using Laser Heated Pedestal Growth (LHPG) method and characterized for its

  1. Guest exchange through single crystal-single crystal transformations in a flexible hydrogen-bonded framework.

    PubMed

    Xiao, Wenchang; Hu, Chunhua; Ward, Michael D

    2014-10-08

    A molecular framework based on guanidinium cations and 1,2,4,5-tetra(4-sulfonatophenyl)benzene (TSPB), an aromatic tetrasulfonate with nominal 2-fold and mirror symmetry, exhibits three crystallographically unique one-dimensional channels as a consequence of molecular symmetry and complementary hydrogen bonding between the guanidinium (G) ions and the sulfonate (S) groups of TSPB. Unlike previous GS frameworks, this new topology is sufficiently flexible to permit reversible release and adsorption of guest molecules in large single crystals through a cyclic shrinkage and expansion of the channels with retention of single crystallinity, as verified by single crystal X-ray diffraction. Moreover, the G4TSPB framework permits guest exchange between various guest molecules through SCSCTs as well as exchange discrimination based on the size and character of the three different channels. The exchange of guest molecules during single crystal-single crystal transformations (SCSCT), a rare occurrence for hydrogen-bonded frameworks, is rather fast, with diffusivities of approximately 10(-6) cm(2) s(-1). Rapid diffusion in the two channels having cross sections sufficient to accommodate two guest molecules can be explained by two-way or ring diffusion, most likely vacancy assisted. Surprisingly, rapid guest exchange also is observed in a smaller channel having a cross-section that accommodates only one guest molecule, which can only be explained by guest-assisted single-file unidirectional diffusion. Several single crystals of inclusion compounds can be realized only through guest exchange in the intact framework, suggesting an approach to the synthesis of single crystalline inclusion compounds that otherwise cannot be attained through direct crystallization methods.

  2. Novel biphenyl-substituted 1,2,4-oxadiazole ferroelectric liquid crystals: synthesis and characterization

    PubMed Central

    Subrao, Mahabaleshwara; Potukuchi, Dakshina Murthy; Sharada Ramachandra, Girish; Bhagavath, Poornima; Bhat, Sangeetha G

    2015-01-01

    Summary Two novel series of unsymmetrically substituted 1,2,4-oxadiazole viz., R.Ox.C*Cn compounds are synthesized and characterized. An optically active, (S)-(+)-methyl 3-hydroxy-2-methylpropionate is used to introduce a chiral center in the molecule. A biphenyl moiety prepared by Suzuki coupling reaction is directly attached to the oxadiazole core at C-5 position. Investigations for the phase behavior revealed that the series with a benzyl group on one end of the oxadiazole core exhibits an 1D orthogonal smectic-A phase while the second series with dodecyl flexible end chain shows orthogonal smectic-A and tilted chiral smectic-C (SmC*) phases over a wide range of temperatures. The smectic-C phase exhibits ferroelectric (FE) polarization switching. The mesomorphic thermal stabilities of these compounds are discussed in the domain of the symmetry and the flexibility of the alkyloxy end chain length attached to the chiral center. PMID:25815075

  3. Single-crystal to single-crystal transformations in discrete hydrated dimeric copper complexes.

    PubMed

    Mobin, Shaikh M; Srivastava, Ashwini K; Mathur, Pradeep; Lahiri, Goutam Kumar

    2010-02-14

    The single crystals of discrete hydrated [(OAc)Cu(mu-hep)(2)Cu(OAc)].2H(2)O (.2H(2)O) and [(OAc)Cu(mu-hep)(2) Cu(O(n)Pr)].2H(2)O (.2H(2)O) (the lattice H(2)O molecules exist as a tetrameric water cluster, hep-H = 2-(2-hydroxyethyl)pyridine), OAc(-) = acetate and O(n)Pr(-) = n-propionate) undergo single-crystal to single-crystal (SCSC) transformations to the dehydrated and , respectively, under the influence of heat. The reverse SCSC processes of /-->.2H(2)O/.2H(2)O involving the regeneration of the lattice water tetramers take place on exposure of / to water vapour. However, the blue single crystal of discrete hydrated [(O(n)Pr)Cu(mu-hep)(2)Cu(O(n)Pr)].2H(2)O (.2H(2)O), incorporating the two bulkier O(n)Pr(-) terminal bidentate ligands, irreversibly converts to the green single crystal of a unique discrete tetrameric [Cu(4)(mu(3)hep)(2)(mu-hep)(2)(mu-O(n)Pr)(2)(O(n)Pr)(2)] () with double open cubane core either by heating or by a simple vapour diffusion technique via the breaking and forming of multiple covalent bonds.

  4. Gas hydrate single-crystal structure analyses.

    PubMed

    Kirchner, Michael T; Boese, Roland; Billups, W Edward; Norman, Lewis R

    2004-08-04

    The first single-crystal diffraction studies on methane, propane, methane/propane, and adamantane gas hydrates SI, SII, and SH have been performed. To circumvent the problem of very slow crystal growth, a novel technique of in situ cocrystallization of gases and liquids resulting in oligocrystalline material in a capillary has been developed. With special data treatment, termed oligo diffractometry, structural data of the gas hydrates of methane, acetylene, propane, a propane/ethanol/methane-mixture and an adamantane/methane-mixture were obtained. Cell parameters are in accord with reported values. Host network and guest are subject to extensive disorder, reducing the reliability of structural information. It was found that most cages are fully occupied by a guest molecule with the exception of the dodecahedral cage in the acetylene hydrate which is only filled to 60%. For adamantane in the icosahedral cage a disordered model is proposed.

  5. Single crystal to single crystal polymerization of a columnar assembled diacetylene macrocycle

    NASA Astrophysics Data System (ADS)

    Xu, Weiwei

    Organic tubular materials have attracted lots of attentions for their potential applications as nanoscale fluidic transport systems, specific ion sensors, molecular sieves and confined molecular reaction containers. While conjugated polymers, due to delocalized Pi electrons, exhibit interesting solar cells and sensors applications. In this thesis, we developed a conjugated polymer which combines the attributes of conjugated polymers with tubular materials, which should have great potential to work as a sensing material. We reproduced and scaled-up the synthesis of a polymerizable macrocycle 1 that contains two rigidly separated diacetylene units. We found that, through hydrogen bonding, 1 can assemble into columnar crystals and can be polymerized under a single crystal to single crystal transformation process to afford porous polydiacetylene (PDA) crystals. We studied the assembly of the macrocycles 1 under different conditions to give three different crystalline forms and micro-phase crystals, and also investigated their subsequent polymerizations. The macrocycle assembly and polymerized materials were characterized by a variety of technique. Since the gas adsorption measurement exhibited PDA crystals still retained its porosity and the polymer should have ability to uptake suitable guest molecules, therefore the absorption of iodine for PDA crystals was investigated as well.

  6. Direct shear of olivine single crystals

    NASA Astrophysics Data System (ADS)

    Tielke, Jacob A.; Zimmerman, Mark E.; Kohlstedt, David L.

    2016-12-01

    Knowledge of the strengths of the individual dislocation slip systems in olivine is fundamental to understanding the flow behavior and the development of lattice-preferred orientation in olivine-rich rocks. The most direct measurements of the strengths of individual slip systems are from triaxial compression experiments on olivine single crystals. However, such experiments only allow for determination of flow laws for two of the four dominant slip systems in olivine. In order to measure the strengths of the (001)[100] and (100)[001] slip systems independently, we performed deformation experiments on single crystals of San Carlos olivine in a direct shear geometry. Experiments were carried out at temperatures of 1000 ° to 1300 °C, a confining pressure of 300 MPa, shear stresses of 60 to 334 MPa, and resultant shear strain rates of 7.4 × 10-6 to 2.1 × 10-3 s-1. At high-temperature (≥1200 °C) and low-stress (≤200 MPa) conditions, the strain rate of crystals oriented for direct shear on either the (001)[100] or the (100)[001] slip system follows a power law relationship with stress, whereas at lower temperatures and higher stresses, strain rate depends exponentially on stress. The flow laws derived from the mechanical data in this study are consistent with a transition from the operation of a climb-controlled dislocation mechanism during power-law creep to the operation of a glide-controlled dislocation mechanism during exponential creep. In the climb-controlled regime, crystals oriented for shear on the (001)[100] slip system are weaker than crystals orientated for shear on the (100)[001] slip system. In contrast, in the glide-controlled regime the opposite is observed. Extrapolation of flow laws determined for crystals sheared in orientations favorable for slip on these two slip systems to upper mantle conditions reveals that the (001)[100] slip system is weaker at temperatures and stresses that are typical of the asthenospheric mantle, whereas the (100

  7. Direct Shear of Olivine Single Crystals

    NASA Astrophysics Data System (ADS)

    Tielke, Jacob; Zimmerman, Mark; Kohlstedt, David

    2016-04-01

    Knowledge of the strength of individual dislocation slip systems in olivine is fundamental to understanding the flow behavior and the development of lattice-preferred orientation in olivine-rich rocks. The most direct measurements of the strengths of individual slip systems are from triaxial compression experiments on olivine single crystals. However, such experiments only allow for determination of flow laws for two of the four dominate slip systems in olivine. In order to measure the strengths of the (001)[100] and (100)[001] slip systems independently, we performed deformation experiments on single crystals of San Carlos olivine in a direct shear geometry. Experiments were carried out at temperatures of 1000° to 1300°C, a confining pressure of 300 MPa, shear stresses of 60 to 334 MPa, and resultant shear strain rates of 7.4 x 10-6 to 6.7 x 10-4 s-1. At high-temperature (≥1200°C) and low-stress (≤200 MPa) conditions, the strain rate of crystals oriented for direct shear on either the (001)[100] or the (100)[001] slip system follows a power law relationship with stress, whereas at lower temperatures and higher stresses, strain rate depends exponentially on stress. The flow laws derived from the mechanical data in this study are consistent with a transition from the operation of a climb-controlled dislocation mechanism during power-law creep to the operation of a glide-controlled dislocation mechanism during exponential creep. In the climb-controlled regime, crystals oriented for shear on the (001)[100] slip system are weaker than crystals orientated for shear on the (100)[001] slip system. In contrast, in the glide-controlled regime the opposite is observed. Extrapolation of flow laws determined for crystals sheared in orientations favorable for slip on these two slip systems to upper mantle conditions reveals that the (001)[100] slip system is weaker at temperatures and stresses that are typical of the asthenospheric mantle, whereas the (100)[001] slip

  8. Ferroelectric Pump

    NASA Technical Reports Server (NTRS)

    Jalink, Antony, Jr. (Inventor); Hellbaum, Richard F. (Inventor); Rohrbach, Wayne W. (Inventor)

    2000-01-01

    A ferroelectric pump has one or more variable volume pumping chambers internal to a housing. Each chamber has at least one wall comprising a dome shaped internally prestressed ferroelectric actuator having a curvature and a dome height that varies with an electric voltage applied between an inside and outside surface of the actuator. A pumped medium flows into and out of each pumping chamber in response to displacement of the ferroelectric actuator. The ferroelectric actuator is mounted within each wall and isolates each ferroelectric actuator from the pumped medium, supplies a path for voltage to be applied to each ferroelectric actuator, and provides for positive containment of each ferroelectric actuator while allowing displacement of the entirety of each ferroelectric actuator in response to the applied voltage.

  9. Chemical vapor deposition of graphene single crystals.

    PubMed

    Yan, Zheng; Peng, Zhiwei; Tour, James M

    2014-04-15

    As a two-dimensional (2D) sp(2)-bonded carbon allotrope, graphene has attracted enormous interest over the past decade due to its unique properties, such as ultrahigh electron mobility, uniform broadband optical absorption and high tensile strength. In the initial research, graphene was isolated from natural graphite, and limited to small sizes and low yields. Recently developed chemical vapor deposition (CVD) techniques have emerged as an important method for the scalable production of large-size and high-quality graphene for various applications. However, CVD-derived graphene is polycrystalline and demonstrates degraded properties induced by grain boundaries. Thus, the next critical step of graphene growth relies on the synthesis of large graphene single crystals. In this Account, we first discuss graphene grain boundaries and their influence on graphene's properties. Mechanical and electrical behaviors of CVD-derived polycrystalline graphene are greatly reduced when compared to that of exfoliated graphene. We then review four representative pathways of pretreating Cu substrates to make millimeter-sized monolayer graphene grains: electrochemical polishing and high-pressure annealing of Cu substrate, adding of additional Cu enclosures, melting and resolidfying Cu substrates, and oxygen-rich Cu substrates. Due to these pretreatments, the nucleation site density on Cu substrates is greatly reduced, resulting in hexagonal-shaped graphene grains that show increased grain domain size and comparable electrical properties as to exfoliated graphene. Also, the properties of graphene can be engineered by its shape, thickness and spatial structure. Thus, we further discuss recently developed methods of making graphene grains with special spatial structures, including snowflakes, six-lobed flowers, pyramids and hexagonal graphene onion rings. The fundamental growth mechanism and practical applications of these well-shaped graphene structures should be interesting topics and

  10. Optical properties of lithium niobate single crystals

    NASA Astrophysics Data System (ADS)

    Palatnikov, M. N.; Sidorov, N. V.; Biryukova, I. V.; Kalinnikov, V. T.; Bormanis, K.

    2005-01-01

    Studies of thermal and -irradiation effects on the optical properties in congruous lithium niobate single crystals containing Y, Mg, Gd, B, and Zn dopants including samples with double dopants Y, Mg and Gd, Mg are reported. Formation of defects at irradiation and thermal treatment of the samples is explored by electron absorption spectra. Considerable increase of absorption with the dose of -radiation is observed at 500 nm. The changes of absorption examined under different conditions are explained by creation and destruction of Nb4+ defects.

  11. Phase transition in sarcosine phosphite single crystals

    NASA Astrophysics Data System (ADS)

    Lemanov, V. V.; Popov, S. N.; Pankova, G. A.

    2011-06-01

    Single crystals of sarcosine phosphite (SarcH3PO3) have been grown. The amino acid sarcosine is an isomer of the protein amino acid alanine. Both amino acids are described by the same chemical formula but have different structures; or, more specifically, in contrast to the alanine molecule, the sarcosine molecule has a symmetric structure. It has been found that the sarcosine phosphite compound undergoes a structural phase transition at a temperature of approximately 200 K. This result has demonstrated that compounds of achiral amino acids are more susceptible to structural phase transitions.

  12. Conduction mechanism of single-crystal alumina

    NASA Technical Reports Server (NTRS)

    Will, Fritz G.; Delorenzi, Horst G.; Janora, Kevin H.

    1992-01-01

    The fully guarded three-terminal technique was used to perform conductivity measurements on single-crystal alumina at temperatures of 400-1300 C. The conductivity was also determined as a function of time at various temperatures and applied fields. Further, the fractions of the current carried by Al and O ions (ionic transference numbers) were determined from long-term transference experiments in the temperature range 1100-1300 C. A mathematical model of the conduction mechanism is proposed, and model predictions are compared with experimental results.

  13. High-Energy Synchrotron X-Ray Diffraction for In Situ Diffuse Scattering Studies of Bulk Single Crystals

    NASA Astrophysics Data System (ADS)

    Daniels, John E.; Jo, Wook; Donner, Wolfgang

    2012-01-01

    High-energy synchrotron x-ray scattering offers a powerful technique for investigation of single-crystal material structures. Large, mm-sized crystals can be used, allowing complex in situ sample environments to be employed. Here, we demonstrate how this technique can be applied for the collection of single-crystal diffuse scattering volumes from the electro-active material 96%Bi0.5Na0.5TiO3-4%BaTiO3 while electric fields are applied in situ. The data obtained allow correlation of the atomic and nanoscale structures with the observed macroscopic electro-active properties of interest. This article presents a recent study relating the nanoscale stacking fault structure in BNT-BT to the relaxor-ferroelectric nature of the material [Daniels et al. in Appl. Phys. Lett. 98, 252904 (2011)], and extends this study with further experimental description and analysis.

  14. Thermodynamic forces in single crystals with dislocations

    NASA Astrophysics Data System (ADS)

    Van Goethem, Nicolas

    2014-06-01

    A simple model for the evolution of macroscopic dislocation regions in a single crystal is presented. This model relies on maximal dissipation principle within Kröner's geometric description of the dislocated crystal. Mathematical methods and tools from shape optimization theory provide equilibrium relations at the dislocation front, similarly to previous work achieved on damage modelling (J Comput Phys 33(16):5010-5044, 2011). The deformation state variable is the incompatible strain as related to the dislocation density tensor by a relation involving the Ricci curvature of the crystal underlying elastic metric. The time evolution of the model variables follows from a novel interpretation of the Einstein-Hilbert flow in terms of dislocation microstructure energy. This flow is interpreted as the dissipation of non-conservative dislocations, due to the climb mechanism, modelled by an average effect of mesoscopic dislocations moving normal to their glide planes by adding or removing points defects. The model equations are a fourth-order tensor parabolic equation involving the operator "incompatibility," here appearing as a tensorial counterpart of the scalar Laplacian. This work encompasses and generalizes results previously announced (C R Acad Sci Paris Ser I 349:923-927, 2011), with in addition a series of physical interpretations to give a meaning to the newly introduced concepts.

  15. Heterogeneous growth of single crystals on polycrystals

    NASA Astrophysics Data System (ADS)

    Wang, Zumin; Jeurgens, Lars P. H.; Gu, Lin; Mittemeijer, Eric J.

    2017-03-01

    This work discloses a surprising, previously unknown heterogeneous growth mode. Namely, large-area, thin sheets of single-crystalline Ge were observed to grow laterally on top of a polycrystalline Al substrate, covering as many as tens of differently oriented Al grains at low temperatures. The observation of the Ge crystal-growth process by in situ heating transmission electron microscopy demonstrates an intriguing type of "faceted" growth: the growth of single-crystalline Ge thin sheets proceeding Al-grain by Al-grain on top of the polycrystalline Al substrate. The crystalline Ge growth front tends to align along the lines of intersection of the Al grain boundaries with the Al surface. Such an unusual heterogeneous growth mode has been shown to be a consequence of the strong anisotropy of the energy of the crystalline/crystalline (here: c-Ge/c-Al) interfaces.

  16. Biaxial constitutive equation development for single crystals

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.

    1984-01-01

    Current gas turbine engines utilize large single crystal superalloy components in the hot section. Structural analysis of these components requires a valid stress strain temperature constitutive equation. The goal of the program described is to create one or more models and verify these models. A constitutive equation based on an assumed slip behavior of a single slip system was formulated, programmed, and debugged. Specifically, the basic theory for a model based on aggravating slip behavior on individual slip systems was formulated and programmed and some simulations were run using assumed values of constants. In addition, a formulation allowing strain controlled simulations was completed. An approach to structural analysis of the specimen was developed. This approach uses long tube consistancy conditions and finite elements specially formulated to take advantage of the symmetry of 100 oriented specimens.

  17. Cutting fluid study for single crystal silicon

    SciTech Connect

    Chargin, D.

    1998-05-05

    An empirical study was conducted to evaluate cutting fluids for Single Point Diamond Turning (SPDT) of single crystal silicon. The pH of distilled waster was adjusted with various additives the examine the effect of pH on cutting operations. Fluids which seemed to promote ductile cutting appeared to increase tool wear as well, an undesirable tradeoff. High Ph sodium hydroxide solutions showed promise for further research, as they yielded the best combination of reduced tool wear and good surface finish in the ductile regime. Negative rake tools were verified to improve the surface finish, but the negative rake tools used in the experiments also showed much higher wear than conventional 0{degree} rake tools. Effects of crystallographic orientation on SPDT, such as star patterns of fracture damage forming near the center of the samples, were observed to decrease with lower feedrates. Silicon chips were observed and photographed, indicative of a ductile materials removal process.

  18. Electro-Optical Properties of Ferroelectric Liquid Crystals with a Sulfinate Group as Unique Source of Chirality

    NASA Astrophysics Data System (ADS)

    Zoubair Cherkaoui, Mohammed; Nicoud, Jean-François; Galerne, Yves; Guillon, Daniel

    1995-09-01

    In this communication, we present the first electro-optical measurements performed on ferroelectric liquid crystals materials based on molecules containing a sulfinate group as the unique chiral source. Spontaneous polarization, response time to the applied electric field and tilt angle of the molecules as a function of temperature are reported for two representative molecules of the whole series. It is also shown the existence of a significant electroclinic effect in the smectic A phase. Dans cette communication, nous rapportons les premières mesures électro-optiques sur des cristaux liquides ferroélectriques obtenus à partir de molécules contenant un groupe sulfinate comme centre unique de chiralité. Sont présentés la polarisation spontanée, le temps de réponse au champ électrique appliqué et l'angle d'inclinaison des molécules en fonction de la température pour deux molécules typiques de la série homologue. Il est aussi mis en évidence un fort effet électroclinique dans la phase smectique A.

  19. Magnetoelastic wave tunneling via a gap between ferroelectric crystals with relative longitudinal displacement

    NASA Astrophysics Data System (ADS)

    Vilkov, E. A.; Moiseev, A. V.; Shavrov, V. G.

    2009-09-01

    The tunneling of a plane monochromatic acoustic wave via a gap between two ferromagnetic crystals exhibiting relative longitudinal displacement has been studied. It is shown that, at a gap width comparable with the wavelength, the acoustic wave can exhibit complete transmission at the Damon-Eshbach mode frequency. If the gap width is much smaller than the wavelength, the complete transmission takes place at two resonance frequencies. Allowance for the longitudinal displacement of one crystal leads in all cases to violation of the resonance conditions, which results in a significant decrease in the transmission coefficient. The greater the velocity of crystal displacement, the stronger the decrease in the acoustic wave transmission though the gap between ferromagnetic crystals.

  20. Accelerated domain switching speed in single-crystal LiNbO{sub 3} thin films

    SciTech Connect

    Jiang, J.; Jiang, A. Q.; Meng, X. J.; Geng, D. Q.

    2015-03-14

    By using ionic implantation and wafer bonding technologies, we peeled off a single-crystal LiNbO{sub 3} thin film in the atomic-layer smoothness from the surface of a bulk Z-cut LiNbO{sub 3} single crystal. X-ray diffraction patterns showed only (00l) orientation of the film. From positive-up-negative–down pulse characterization, we measured domain switching current transients under various short-pulse voltages, where we observed domain switching currents to occur separately at time after initial capacitor charging currents. This is similar to early observations in bulk ferroelectric single crystals, where apparent positive/negative coercive fields of domain switching determined from polarization-electric field hysteresis loops always equal maximum/minimum applied fields. However, after pulse stressing of the film for more than 1000 cycles, the domain switching speed is accelerated, where domain switching current overlaps with the initial capacitor charging current with a well-defined coercive field independent of the applied-field strength. Finally, we simulated the whole domain switching current transients with the assumption of the resistance degradation across interfacial passive layers between the film and electrodes.

  1. Growing single crystals in silica gel

    NASA Technical Reports Server (NTRS)

    Rubin, B.

    1970-01-01

    Two types of chemical reactions for crystal growing are discussed. The first is a metathetical reaction to produce calcium tartrate tetrahydrate crystals, the second is a decomplexation reaction to produce cuprous chloride crystals.

  2. Characterization of Pb(In(12)Nb(12))O(3)-Pb(Mg(13)Nb(23))O(3)-PbTiO(3) ferroelectric crystal with enhanced phase transition temperatures.

    PubMed

    Zhang, Shujun; Luo, Jun; Hackenberger, Wesley; Shrout, Thomas R

    2008-09-15

    The full set of material constants for relaxor-based ternary single crystals Pb(In(12)Nb(12))O(3)-Pb(Mg(13)Nb(23))O(3)-PbTiO(3) (PIN-PMN-PT) were determined and compared to binary Pb(Mg(13)Nb(23))O(3)-PbTiO(3) (PMNT) crystals. The Curie temperature for rhombohedral compositions of PIN-PMN-PT was found to be in the range of 160-200 degrees C with ferroelectric rhombohedral to tetragonal phase transition on the order of 120-130 degrees C, more than 30 degrees C higher than that found for PMNT. The piezoelectric coefficients (d(33)) were in the range of 1100-1500 pCN, with electromechanical coupling factors (k(33)) about 89%-92% comparable to PMNT crystals. The coercive field of the ternary crystal was found to be 5.5 kVcm, double the value of the binary counterparts. The dielectric behavior under varying dc bias exhibited a similar trend as observed in PMNT with a much broader usage temperature range. Together with its enhanced field induced phase transition level, the ternary PIN-PMN-PT crystals are promising candidates for high temperature and high drive transducer applications.

  3. Growth of single crystals of BaFe12O19 by solid state crystal growth

    NASA Astrophysics Data System (ADS)

    Fisher, John G.; Sun, Hengyang; Kook, Young-Geun; Kim, Joon-Seong; Le, Phan Gia

    2016-10-01

    Single crystals of BaFe12O19 are grown for the first time by solid state crystal growth. Seed crystals of BaFe12O19 are buried in BaFe12O19+1 wt% BaCO3 powder, which are then pressed into pellets containing the seed crystals. During sintering, single crystals of BaFe12O19 up to ∼130 μm thick in the c-axis direction grow on the seed crystals by consuming grains from the surrounding polycrystalline matrix. Scanning electron microscopy-energy dispersive spectroscopy analysis shows that the single crystal and the surrounding polycrystalline matrix have the same chemical composition. Micro-Raman scattering shows the single crystal to have the BaFe12O19 structure. The optimum growth temperature is found to be 1200 °C. The single crystal growth behavior is explained using the mixed control theory of grain growth.

  4. Piezoelectric single crystals for ultrasonic transducers in biomedical applications.

    PubMed

    Zhou, Qifa; Lam, Kwok Ho; Zheng, Hairong; Qiu, Weibao; Shung, K Kirk

    2014-10-01

    Piezoelectric single crystals, which have excellent piezoelectric properties, have extensively been employed for various sensors and actuators applications. In this paper, the state-of-art in piezoelectric single crystals for ultrasonic transducer applications is reviewed. Firstly, the basic principles and design considerations of piezoelectric ultrasonic transducers will be addressed. Then, the popular piezoelectric single crystals used for ultrasonic transducer applications, including LiNbO3 (LN), PMN-PT and PIN-PMN-PT, will be introduced. After describing the preparation and performance of the single crystals, the recent development of both the single-element and array transducers fabricated using the single crystals will be presented. Finally, various biomedical applications including eye imaging, intravascular imaging, blood flow measurement, photoacoustic imaging, and microbeam applications of the single crystal transducers will be discussed.

  5. Experimental dynamic metamorphism of mineral single crystals

    USGS Publications Warehouse

    Kirby, S.H.; Stern, L.A.

    1993-01-01

    This paper is a review of some of the rich and varied interactions between non-hydrostatic stress and phase transformations or mineral reactions, drawn mainly from results of experiments done on mineral single crystals in our laboratory or our co-authors. The state of stress and inelastic deformation can enter explicitly into the equilibrium phase relations and kinetics of mineral reactions. Alternatively, phase transformations can have prominent effects on theology and on the nature of inelastic deformation. Our examples represent five types of structural phase changes, each of which is distinguished by particular mechanical effects. In increasing structural complexity, these include: (1) displacive phase transformations involving no bond-breaking, which may produce anomalous brittle behavior. A primary example is the a-?? quartz transition which shows anomalously low fracture strength and tertiary creep behavior near the transition temperature; (2) martensitic-like transformations involving transformation strains dominated by shear deformation. Examples include the orthoenstatite ??? clinoenstatite and w u ??rtzite ??? sphalerite transformations; (3) coherent exsolution or precipitation of a mineral solute from a supersaturated solid-solution, with anisotropy of precipitation and creep rates produced under nonhydrostatic stress. Examples include exsolution of corundum from MgO ?? nAl2O3 spinels and Ca-clinopyroxene from orthopyroxene; (4) order-disorder transformations that are believed to cause anomalous plastic yield strengthening, such as MgO - nAl2O3 spinels; and (5) near-surface devolatilization of hydrous silicate single-crystals that produces a fundamental brittleness thought to be connected with dehydration at microcracks at temperatures well below nominal macroscopic dehydration temperatures. As none of these interactions between single-crystal phase transformations and non-hydrostatic stress is understood in detail, this paper serves as a challenge to

  6. Solar cell structure incorporating a novel single crystal silicon material

    DOEpatents

    Pankove, Jacques I.; Wu, Chung P.

    1983-01-01

    A novel hydrogen rich single crystal silicon material having a band gap energy greater than 1.1 eV can be fabricated by forming an amorphous region of graded crystallinity in a body of single crystalline silicon and thereafter contacting the region with atomic hydrogen followed by pulsed laser annealing at a sufficient power and for a sufficient duration to recrystallize the region into single crystal silicon without out-gassing the hydrogen. The new material can be used to fabricate semiconductor devices such as single crystal silicon solar cells with surface window regions having a greater band gap energy than that of single crystal silicon without hydrogen.

  7. Growth and studies of pure and potassium iodide-doped zinc tris-thiourea sulphate (ZTS) single crystals

    NASA Astrophysics Data System (ADS)

    Krishnan, C.; Selvarajan, P.; Freeda, T. H.

    2008-12-01

    Single crystals of pure and potassium iodide (KI)-doped Zinc Tris-thiourea Sulphate (ZTS) were grown from aqueous solutions by slow evaporation technique. The grown crystals have been subjected to single crystal X-ray diffraction to determine the unit cell dimensions. The grown crystals were also characterized by recording the powder X-ray diffraction patterns and by identifying the diffracting planes. The Fourier Transform Infrared (FT-IR) spectra have been recorded in the range 400-4500 cm -1. Second harmonic generation (SHG) for the materials of this work was confirmed using Nd:YAG laser. The UV-visible spectra show that the grown crystals have wide optical transparency in the entire visible region. The Thermogravimetric/Differential Thermal Analyses (TG/DTA) thermograms reveal that the materials have good thermal stability. Atomic absorption study reveals the presence of potassium in the doped f crystals. The electrical measurements were made in the temperature range 40-130 °C along c-direction of the grown crystals. The dielectric studies show that there may be a ferroelectric transition at 50 °C for both pure and KI-doped ZTS crystals. DC conductivity for both the samples is found to be increasing with increase in temperature. Activation energy values were also determined for both AC and DC conduction processes in the samples.

  8. Mechanical properties of single crystal YAg

    SciTech Connect

    Russell, A.M.; Zhang, Z.; Lograsso, T.A.; Lo, C.C.H.; Pecharsky, A.O.; Morris, J.R.; Ye, Y.; Gschneidner, K.A.; Slager, A.J

    2004-08-02

    YAg, a rare earth-precious metal 'line compound', is one member of the family of B2 rare earth intermetallic compounds that exhibit high ductilities. Tensile tests of polycrystalline YAg specimens have produced elongations as high as 27% before failure. In the present work, single crystal specimens of YAg with the B2, CsCl-type crystal structure were tensile tested at room temperature. Specimens with a tensile axis orientation of [0 1 1-bar] displayed slip lines on the specimen faces corresponding to slip on the {l_brace}1 1 0{r_brace}<0 1 0> with a critical resolved shear stress of 13 MPa. A specimen with a tensile axis orientation of [1 0 0] showed no slip lines and began to crack at a stress of 300 MPa. The test specimens also displayed some slip lines whose position corresponded to slip on the {l_brace}1 0 0{r_brace}<0 1 0>; these slip lines were found near intersections of {l_brace}1 1 0{r_brace}<0 1 0> slip lines, which suggests that the {l_brace}1 0 0{r_brace}<0 1 0> may be a secondary slip system in YAg. Transmission electron microscope (TEM) examination of the crystals was performed after tensile testing and the dislocations observed were analyzed by g {center_dot} b=0 out of contrast analysis. This TEM analysis indicated that the predominant Burgers vector for the dislocations present was <1 1 1> with some <0 1 1> dislocations also being observed. This finding is inconsistent with the <0 1 0> slip direction determined by slip line analysis, and possible explanations for this surprising finding are presented.

  9. Coexistence of multiple positive and negative electrocaloric responses in (Pb, La)(Zr, Sn, Ti)O3 single crystal

    NASA Astrophysics Data System (ADS)

    Zhuo, Fangping; Li, Qiang; Gao, Jinghan; Wang, Yujie; Yan, Qingfeng; Zhang, Yiling; Xi, Xiaoqing; Chu, Xiangcheng; Cao, Wenwu

    2016-02-01

    The electrocaloric effect has been investigated in antiferroelectric (Pb, La)(Zr, Sn, Ti)O3 (PLZST) single crystals grown by the flux method. The measurements of polarization versus electric field loops on unpoled crystals revealed that at room temperature, a critical electric field of 1.8 kV/mm is needed to induce a ferroelectric phase from an antiferroelectric phase. The dielectric properties demonstrated that the induced ferroelectric phase recovers to antiferroelectric phase when temperature is above the depolarization temperature (70 °C-100 °C). Coexistence of the negative and positive electrocaloric effect has been achieved in ⟨001⟩-oriented PLZST single crystals. Multiple electrocaloric response values of -0.054 °C at room temperature, 0.17 °C near the depolarization temperature, -0.14 °C at 125 °C, and 0.75 °C around Curie temperature have been observed under an electric field of 3 kV/mm. The coexistence of multiple negative and positive electrocaloric effects in one material provides a possibility to design solid-state refrigerator technologies to enhance the electrocaloric efficiency.

  10. Noncontact atomic force microscopy of perfect single crystals of pentacene prepared by crystallization from solution.

    PubMed

    Sato, Kazuya; Sawaguchi, Takahiro; Sakata, Masafumi; Itaya, Kingo

    2007-12-18

    Nearly perfect single crystals of pentacene were grown from trichlorobenzene solution. The surface structure of pentacene single crystals has been investigated by frequency modulation atomic force microscopy. Molecularly flat and extraordinarily wide terraces, extended over the width of more than a few micrometers with monomolecular steps, were consistently observed, suggesting that those pentacene crystals were nearly perfect single crystals. Molecular packing arrangements were revealed by FM-AFM for the first time.

  11. Method of Making Lightweight, Single Crystal Mirror

    NASA Technical Reports Server (NTRS)

    Bly, Vincent T. (Inventor)

    2015-01-01

    A method of making a mirror from a single crystal blank may include fine grinding top and bottom surfaces of the blank to be parallel. The blank may then be heat treated to near its melting temperature. An optical surface may be created on an optical side of the blank. A protector may be bonded to the optical surface. With the protector in place, the blank may be light weighted by grinding a non-optical surface of the blank using computer controlled grinding. The light weighting may include creating a structure having a substantially minimum mass necessary to maintain distortion of the mirror within a preset limit. A damaged layer of the non-optical surface caused by light weighting may be removed with an isotropic etch and/or repaired by heat treatment. If an oxide layer is present, the entire blank may then be etched using, for example, hydrofluoric acid. A reflecting coating may be deposited on the optical surface.

  12. Thermal debracketing of single crystal sapphire brackets.

    PubMed

    Rueggeberg, F A; Lockwood, P E

    1992-01-01

    Because of their optical clarity, single crystal sapphire brackets provide an esthetic advantage over many other types of orthodontic brackets. However, debonding of these brackets has caused iatrogenic damage to enamel. Thermal debonding has been proposed for use in removing sapphire brackets without causing damage to teeth. This study determined the temperature required at the enamel/resin interface to thermally debond sapphire brackets from etched bovine enamel using 23 different commercially available orthodontic resins and one experimental product. The results indicate a wide range of debonding temperatures for the various resins. As a group, the powder-liquid materials had a statistically lower debonding temperature than the two-paste, the no-mix products, or the light-cured materials, for which the temperatures were all similar. This paper presents relative information a clinician can use in selecting an orthodontic bonding resin to minimize thermal damage to the teeth while debonding sapphire brackets.

  13. Constitutive modeling for single crystal superalloys

    NASA Technical Reports Server (NTRS)

    Stouffer, Donald C.; Dame, L. Thomas; Jayaraman, N.

    1985-01-01

    A crystallographic approach to constitutive modeling of single crystal superalloys is discussed. The approach is based on identifying the active slip planes and slip directions. The shear stresses are computed on each of the slip planes from applied stress components. The slip rate is then computed on each slip system and the microscopic inelastic strain rates are the sum of the slip in the individual slip systems. The constitutive model was implemented in a finite element code using twenty noted isoparametric solid elements. Constants were determined for octahedral and cube slip systems. These constants were then used to predict tension-compression asymmetry and fatigue loops. Other data was used to model the tensile and creep response.

  14. Controlled Folding of Single Crystal Graphene.

    PubMed

    Wang, Bin; Huang, Ming; Kim, Na Yeon; Cunning, Benjamin V; Huang, Yuan; Qu, Deshun; Chen, Xianjue; Jin, Sunghwan; Biswal, Mandakini; Zhang, Xu; Lee, Sun Hwa; Lim, Hyunseob; Yoo, Won Jong; Lee, Zonghoon; Ruoff, Rodney S

    2017-03-08

    Folded graphene in which two layers are stacked with a twist angle between them has been predicted to exhibit unique electronic, thermal, and magnetic properties. We report the folding of a single crystal monolayer graphene film grown on a Cu(111) substrate by using a tailored substrate having a hydrophobic region and a hydrophilic region. Controlled film delamination from the hydrophilic region was used to prepare macroscopic folded graphene with good uniformity on the millimeter scale. This process was used to create many folded sheets each with a defined twist angle between the two sheets. By identifying the original lattice orientation of the monolayer graphene on Cu foil, or establishing the relation between the fold angle and twist angle, this folding technique allows for the preparation of twisted bilayer graphene films with defined stacking orientations and may also be extended to create folded structures of other two-dimensional nanomaterials.

  15. Vibration-assisted machining of single crystal

    NASA Astrophysics Data System (ADS)

    Zahedi, S. A.; Roy, A.; Silberschmidt, V. V.

    2013-07-01

    Vibration-assisted machining offers a solution to expanding needs for improved machining, especially where accuracy and precision are of importance, such as in micromachining of single crystals of metals and alloys. Crystallographic anisotropy plays a crucial role in determining on overall response to machining. In this study, we intend to address the matter of ultra-precision machining of material at the micron scale using computational modelling. A hybrid modelling approach is implemented that combines two discrete schemes: smoothed particle hydrodynamics and continuum finite elements. The model is implemented in a commercial software ABAQUS/Explicit employing a user-defined subroutine (VUMAT) and used to elucidate the effect of crystallographic anisotropy on a response of face centred cubic (f.c.c.) metals to machining.

  16. Submicron diameter single crystal sapphire optical fiber

    DOE PAGES

    Hill, Cary; Homa, Daniel; Liu, Bo; ...

    2014-10-02

    In this work, a submicron-diameter single crystal sapphire optical fiber was demonstrated via wet acid etching at elevated temperatures. Etch rates on the order 2.3 µm/hr were achievable with a 3:1 molar ratio sulfuric-phosphoric acid solution maintained at a temperature of 343°C. A sapphire fiber with an approximate diameter of 800 nm was successfully fabricated from a commercially available fiber with an original diameter of 50 µm. The simple and controllable etching technique provides a feasible approach to the fabrication of unique waveguide structures via traditional silica masking techniques. The ability to tailor the geometry of sapphire optical fibers ismore » the first step in achieving optical and sensing performance on par with its fused silica counterpart.« less

  17. Submicron diameter single crystal sapphire optical fiber

    SciTech Connect

    Hill, Cary; Homa, Daniel; Liu, Bo; Yu, Zhihao; Wang, Anbo; Pickrell, Gary

    2014-10-02

    In this work, a submicron-diameter single crystal sapphire optical fiber was demonstrated via wet acid etching at elevated temperatures. Etch rates on the order 2.3 µm/hr were achievable with a 3:1 molar ratio sulfuric-phosphoric acid solution maintained at a temperature of 343°C. A sapphire fiber with an approximate diameter of 800 nm was successfully fabricated from a commercially available fiber with an original diameter of 50 µm. The simple and controllable etching technique provides a feasible approach to the fabrication of unique waveguide structures via traditional silica masking techniques. The ability to tailor the geometry of sapphire optical fibers is the first step in achieving optical and sensing performance on par with its fused silica counterpart.

  18. CVT Growth of Single Crystal Zinc Oxide

    NASA Astrophysics Data System (ADS)

    Kjar, Michael J.; Boone, Jack L.; Cantwell, Gene; Thomas, J. E.

    1997-03-01

    The growth of single crystal ZnO by chemical vapor transport using hydrogen as the transporting agent is being investigated both theoretically and experimentally. A mathematical model has been developed for the growth process using a quasi-equilibrium approach. By calculating the equilibrium constants at both the source and growing ends of the growth ampoule, a transport equation has been developed. The transport calculations have been made under the assumption of a "leaky" ampoule in which the hydrogen , water vapor, and inert gas pressures can be controlled externally. The chemical reactions at the source and growth surfaces are being investigated to ascertain their effect on the transport and growth processes. Also, the effects of varying the "communication" between the ampoule interior and the large containment vessel on the overall growth process have been investigated. The parameters for the growth process are being refined through a correlation of the theoretical model predictions with experimental data.

  19. Pyroelectric, piezoelectric, and dielectric properties of beta-BaB2O4 single crystal

    NASA Astrophysics Data System (ADS)

    Guo, R.; Bhalla, A. S.

    1989-12-01

    Results are presented on measurements of dielectric and pyroelectric properties of single-crystal beta-BaB2O4 in the temperature range between 50 and -190 C, and of piezoelectric properties at room temperature. The piezoelectric and electromechanical coupling coefficients of this material were found to be rather low, indicating that beta-BaB2O4 is not suitable for piezoelectric transducer applications. On the other hand, the calculated pyroelectric figure of merit p/K was found to remain constant (compared to the p/K of many ferroelectric materials, in which p/K value decreases with the decrease in temperature), making the beta-BaB2O4 an attractive candidate for some device applications.

  20. A simple low-cost single-crystal NMR setup.

    PubMed

    Vinding, Mads S; Kessler, Tommy O; Vosegaard, Thomas

    2016-08-01

    A low-cost single-crystal NMR kit is presented along with a web-based post-processing software. The kit consists of a piezo-crystal motor and a goniometer for the crystal, both embedded in a standard wide-bore NMR probe with a 3D printed scaffold. The NMR pulse program controls the angle setting automatically, and the post-processing software incorporates a range of orientation-angle discrepancies present in the kit and other single-crystal setups. Results with a NaNO3 single-crystal show a high degree of reproducibility and excellent agreement with previous findings for the anisotropic quadrupolar interaction.

  1. A simple low-cost single-crystal NMR setup

    NASA Astrophysics Data System (ADS)

    Vinding, Mads S.; Kessler, Tommy O.; Vosegaard, Thomas

    2016-08-01

    A low-cost single-crystal NMR kit is presented along with a web-based post-processing software. The kit consists of a piezo-crystal motor and a goniometer for the crystal, both embedded in a standard wide-bore NMR probe with a 3D printed scaffold. The NMR pulse program controls the angle setting automatically, and the post-processing software incorporates a range of orientation-angle discrepancies present in the kit and other single-crystal setups. Results with a NaNO3 single-crystal show a high degree of reproducibility and excellent agreement with previous findings for the anisotropic quadrupolar interaction.

  2. Textured ferroelectric thin films: Synthesis, characterization, and influence of compositional grading on the dielectric behavior

    NASA Astrophysics Data System (ADS)

    El-Naggar, Mohamed Y.

    This dissertation focuses on two topics concerning the connections between structure and property in ferroelectric thin films. First, the synthesis of highly oriented ferroelectric thin films is addressed, where the texture is needed to generate high strains that rely on electromechanical domain switching. The ferroelectric films are integrated with oxide electrodes onto single crystal MgO and Si substrates using biaxially-textured MgO as buffer layers. The second topic focuses on modeling the dielectric behavior of compositionally graded ferroelectrics. The functional ferroelectric PbxBa1- xTiO3 films are deposited by metalorganic chemical vapor deposition (MOCVD). SrRuO3, grown by pulsed laser deposition (PLD), is a lattice-matching electrode. Both the ferroelectric and oxide electrode layers are found to inherit the biaxial texture of the underlying MgO template, which can be deposited by ion beam assisted deposition (IBAD) directly on Si-based substrates. In addition, we demonstrated control of the ferroelectric film stoichiometry using a spectroscopic control loop that monitors the ultraviolet spectra of the gas-phase MOCVD precursors during growth. Detailed studies of the microstructural details of these films will be presented. The second topic of this thesis explores the dielectric behavior of functionally graded ferroelectric thin films. Homogenous ferroelectrics offer the possibility of engineering a tunable dielectric response for components in microwave circuits. However, this approach often leads to an undesired temperature sensitivity. Compositionally-graded BaxSr1- xTO3 ferroelectric films have been explored as a means of redressing this sensitivity, but experimental observations vary depending on geometry and other details. A continuum model is presented to calculate the capacitive response of graded ferroelectric films with realistic electrode geometries by accurately accounting for the polarization distribution and long-range electrostatic

  3. Development of novel growth methods for halide single crystals

    NASA Astrophysics Data System (ADS)

    Yokota, Yuui; Kurosawa, Shunsuke; Shoji, Yasuhiro; Ohashi, Yuji; Kamada, Kei; Yoshikawa, Akira

    2017-03-01

    We developed novel growth methods for halide scintillator single crystals with hygroscopic nature, Halide micro-pulling-down [H-μ-PD] method and Halide Vertical Bridgman [H-VB] method. The H-μ-PD method with a removable chamber system can grow a single crystal of halide scintillator material with hygroscopicity at faster growth rate than the conventional methods. On the other hand, the H-VB method can grow a large bulk single crystal of halide scintillator without a quartz ampule. CeCl3, LaBr3, Ce:LaBr3 and Eu:SrI2 fiber single crystals could be grown by the H-μ-PD method and Eu:SrI2 bulk single crystals of 1 and 1.5 inch in diameter could be grown by the H-VB method. The grown fiber and bulk single crystals showed comparable scintillation properties to the previous reports using the conventional methods.

  4. Piezoelectric single crystals for ultrasonic transducers in biomedical applications

    PubMed Central

    Zhou, Qifa; Lam, Kwok Ho; Zheng, Hairong; Qiu, Weibao; Shung, K. Kirk

    2014-01-01

    Piezoelectric single crystals, which have excellent piezoelectric properties, have extensively been employed for various sensors and actuators applications. In this paper, the state–of–art in piezoelectric single crystals for ultrasonic transducer applications is reviewed. Firstly, the basic principles and design considerations of piezoelectric ultrasonic transducers will be addressed. Then, the popular piezoelectric single crystals used for ultrasonic transducer applications, including LiNbO3 (LN), PMN–PT and PIN–PMN–PT, will be introduced. After describing the preparation and performance of the single crystals, the recent development of both the single–element and array transducers fabricated using the single crystals will be presented. Finally, various biomedical applications including eye imaging, intravascular imaging, blood flow measurement, photoacoustic imaging, and microbeam applications of the single crystal transducers will be discussed. PMID:25386032

  5. Study of temperature-dependent Raman spectroscopy and electrical properties in [001]-oriented 0.35Pb(In1/2Nb1/2)O3-0.35Pb(Mg1/3Nb2/3)O3-0.30PbTiO3-Mn single crystals

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Fang, Bijun; Deng, Ji; Yan, Hong; Deng, Hao; Yue, Qingwen; Ding, Jianning; Zhao, Xiangyong; Luo, Haosu

    2016-01-01

    In this work, the temperature-dependent Raman spectra and electrical properties of the [001]-oriented 0.5 mol. % Mn-doped 0.35Pb(In1/2Nb1/2)O3-0.35Pb(Mg1/3Nb2/3)O3-0.30PbTiO3-Mn (PIMNT-Mn) single crystals were investigated. All the unpoled and poled PIMNT-Mn single crystals experience a ferroelectric tetragonal phase to paraelectric cubic phase transition (FET-PC) around 183 °C (TC), which exhibits a second-order transition behavior. Whereas, the poled PIMNT-Mn single crystals exhibit another two dielectric anomalies around 130 °C (TRM) and 148 °C (TMT), in which the ferroelectric rhombohedral phase to ferroelectric monoclinic phase (FER-FEM) and the ferroelectric monoclinic phase to ferroelectric tetragonal phase (FEM-FET) transitions take place, respectively. Both the two ferroelectric phase transitions exhibit a first-order transition behavior. The discontinuous change of the phase degree (θ) and frequencies (fr and fa) around TRM suggest the occurrence of the FER-FEM phase transition in the poled PIMNT-Mn single crystals. The narrowing of the 510 cm-1 and 582 cm-1 Raman modes around the TRM, TMT, and TC temperatures shown in the temperature-dependent Raman spectra suggests their increased ordering of the local structure. The intensity ratio of I272 cm-1/I801 cm-1 increases obviously around the phase transition temperatures (TRM, TMT, and TC), indicating the reduction of the long-range order. The anomalous broadening of the 272 cm-1 Raman mode around the TRM, TMT, and TC temperatures indicates the occurrence of the successive ferroelectric phase transitions (FER-FEM, FEM-FET, and FET-PC) with increasing temperature in the poled PIMNT-Mn single crystals.

  6. Dynamic Actuation of Single-Crystal Diamond Nanobeams

    DTIC Science & Technology

    2014-08-25

    ar X iv :1 40 8. 58 22 v1 [ co nd -m at .m es -h al l] 2 5 A ug 2 01 4 Dynamic Actuation of Single-Crystal Diamond Nanobeams Young-Ik Sohn...United States E-mail: loncar@seas.harvard.edu KEYWORDS: Single-crystal diamond , nanoelectromechanical systems (NEMS), nanofabrica- tion...dielectrophoresis Abstract We show the dielectrophoretic actuation of single-crystal diamond nanomechanical devices using gradient radio-frequency electromagnetic

  7. A comparative study of ultrasonic micro-motors based on single crystal PMN-PT and polycrystalline PZT ceramics

    NASA Astrophysics Data System (ADS)

    Wilson, Stephen A.; Rayner, Philip J.; Gore, Jonathan; Bowles, Adrian R.; McBride, Richard C.

    2008-03-01

    A comparative study has been made to explore the potential benefits of newly available single-crystal ferroelectric materials when used in a practical device, in this case an ultrasonic micro-motor. This type of micro-motor exhibits exceptional power-to-weight characteristics, which could be exploited beneficially, for example, in unmanned air-vehicle (UAV) systems. The operating principles of a range of commercial and experimental motor designs were evaluated objectively in order to identify areas of performance that can potentially be enhanced using PMN-PT single-crystal piezoelectric ceramics. Based on this analysis a practical motor design was selected for construction and experimentation. Detailed numerical analysis indicated that a motor constructed from single crystal PMN-PT could be expected to provide an improvement in motor stall-torque by up to a factor of 2.8 and a no-load speed improvement by a factor of 1.5 when compared with motors based on standard polycrystalline lead-zirconate-titanate (PZT) ceramics. In practice single-crystal versions of the motor were found to produce double the power output of their polycrystalline counterparts. Overall efficiency was found to be improved two-fold. There were significant discrepancies between the numerical predictions for the single-crystal devices and their measured performance, whereas the polycrystalline devices were found to perform closely in line with predictions.

  8. Functionalizing single crystals: incorporation of nanoparticles inside gel-grown calcite crystals.

    PubMed

    Liu, Yujing; Yuan, Wentao; Shi, Ye; Chen, Xiaoqiang; Wang, Yong; Chen, Hongzheng; Li, Hanying

    2014-04-14

    Synthetic single crystals are usually homogeneous solids. Biogenic single crystals, however, can incorporate biomacromolecules and become inhomogeneous solids so that their properties are also extrinsically regulated by the incorporated materials. The discrepancy between the properties of synthetic and biogenic single crystals leads to the idea to modify the internal structure of synthetic crystals to achieve nonintrinsic properties by incorporation of foreign material. Intrinsically colorless and diamagnetic calcite single crystals are turned into colored and paramagnetic solids, through incorporation of Au and Fe3O4 nanoparticles without significantly disrupting the crystalline lattice of calcite. The crystals incorporate the nanoparticles and gel fibers when grown in agarose gel media containing the nanoparticles, whereas the solution-grown crystals do not. As such, our work extends the long-history gel method for crystallization into a platform to functionalize single-crystalline materials.

  9. Double freezing of (NH(4))(2)SO(4)/H(2)O droplets below the eutectic point and the crystallization of (NH(4))(2)SO(4) to the ferroelectric phase.

    PubMed

    Bogdan, A

    2010-09-23

    This paper presents the differential scanning calorimetry (DSC) results obtained from measurements of single droplets of different subeutectic concentrations (<40 wt % (NH4)2SO4) and diameters of 1-1.5 mm. The measurements show that despite the fact that the freezing of the droplets takes place below the eutectic temperature of Te ≈ 254.5 K, a phase separation into ice and a residual freeze-concentrated solution occurs. The residual solution is formed by the expulsion of NH4+ and SO42- ions from the ice lattice during the nucleation and growth of ice and may possess the eutectic concentration of 40 wt % (NH4)2SO4. On further cooling, the residual solution freezes to the eutectic solid mixture of ice/(NH4)2SO4 at a temperature that is either above or below the ferroelectric "Curie" temperature of Tc ≈ 223 K. If the freezing of the residual solution takes place below the Tc, then (NH4)2SO4 crystallizes directly into the ferroelectric phase.

  10. Ultratough CVD single crystal diamond and three dimensional growth thereof

    DOEpatents

    Hemley, Russell J.; Mao, Ho-kwang; Yan, Chih-shiue

    2009-09-29

    The invention relates to a single-crystal diamond grown by microwave plasma chemical vapor deposition that has a toughness of at least about 30 MPa m.sup.1/2. The invention also relates to a method of producing a single-crystal diamond with a toughness of at least about 30 MPa m.sup.1/2. The invention further relates to a process for producing a single crystal CVD diamond in three dimensions on a single crystal diamond substrate.

  11. Effect of an Eu{sup 3+} impurity on the antiferrodistortion and ferroelectric instabilities in an EuTiO{sub 3} bulk crystal and thin films

    SciTech Connect

    Zhandun, V. S. Zamkova, N. G.; Zinenko, V. I.

    2015-01-15

    The existence of an antiferrodistortion transition in EuTiO{sub 3} is disputable, and this question needs to be answered. One of the possible causes is the presence of an Eu{sup 3+} impurity in a sample. A nonempirical polarizable ion model is used to study the effect of a trivalent Eu{sup 3+} ion impurity on the antiferrodistortion and ferroelectric instabilities of an EuTiO{sub 3} crystal in the bulk and the thin-film states. Lattice dynamics calculation shows that a bulk impurity-free EuTiO{sub 3} crystal has no unstable modes throughout the entire phase space volume. The addition of an Eu{sup 3+} impurity leads to a significant softening of the rotational mode, the distortion in which makes tetragonal phase I4/mcm (which is experimentally observed) energetically favorable. In going from the bulk crystal to the thin film, the vibration spectrum of the impurity-free film has unstable antiferrodistortion and rotational modes. The addition of an Eu{sup 3+} impurity enhances the antiferrodistortion instability, which fully or partly suppresses ferroelectricity.

  12. Effect of Ion Trapping Films on the Electrooptic Characteristics of Polymer-Stabilized Ferroelectric Liquid Crystal Display Exhibiting V-Shaped Switching

    NASA Astrophysics Data System (ADS)

    Furuichi, Keiji; Xu, Jun; Inoue, Masaru; Furuta, Hirokazu; Yoshida, Nobuaki; Tounai, Atsushi; Tanaka, Yoshiki; Mochizuki, Akihiro; Kobayashi, Shunsuke

    2003-07-01

    Ion trapping films TOP-COAT TA606B20 are installed beneath the polyimide alignment films, which are coated over the ITO electrode films, in a polymer-stabilized ferroelectric liquid crystal display exhibiting V-shaped switching. The ion trapping films are shown to play the following two roles: one is to remove zigzag-defects owing to their planarizing function and the other is to remove mobile ions. The latter effect gives rise to the reduction of the operational voltage and an increase of the voltage holding ratio owing to the removal of the depolarization field.

  13. Transitions between paraelectric and ferroelectric phases of bent-core smectic liquid crystals in the bulk and in thin freely suspended films

    NASA Astrophysics Data System (ADS)

    Eremin, Alexey; Floegel, Martin; Kornek, Ulrike; Stern, Stephan; Stannarius, Ralf; Nádasi, Hajnalka; Weissflog, Wolfgang; Zhu, Chenhui; Shen, Yongqiang; Park, Cheol Soo; Maclennan, Joseph; Clark, Noel

    2012-11-01

    We report on the contrasting phase behavior of a bent-core liquid crystal with a large opening angle between the mesogenic units in the bulk and in freely suspended films. Second-harmonic generation experiments and direct observation of director inversion walls in films in an applied electric field reveal that the nonpolar smectic C phase observed in bulk samples becomes a ferroelectric “banana” phase in films, showing that a mesogen with a small steric moment can give a phase with polar order in freely suspended films even when the corresponding bulk phase is paraelectric.

  14. Effect of conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) nanotubes on electro-optical and dielectric properties of a ferroelectric liquid crystal.

    PubMed

    Ghosh, S; Nayek, P; Roy, S K; Gangopadhyay, R; Rahaman Molla, M; Majumder, T P

    2011-04-01

    A detailed comparative study of the dielectric and electro-optical properties of a ferroelectric liquid crystal (FLC) and FLC after having doped with conducting polymer Poly (3,4-ethylenedioxythiophene) (PEDOT) nanotubes is done. The electro-optic study reveals a lower electrical response time, rotational viscosity and spontaneous polarization in the FLC/PEDOT nanocomposite system. By fitting the capacitance with voltage in a Preisach model, four dipolar species in both FLC and composites system have been obtained. The orientation of the four dipolar species in the composites system is such that the effective dipole moment in the transverse direction of the FLC molecule is less than that in FLC compound.

  15. Large single domain 123 material produced by seeding with single crystal rare earth barium copper oxide single crystals

    DOEpatents

    Todt, Volker; Miller, Dean J.; Shi, Donglu; Sengupta, Suvankar

    1998-01-01

    A method of fabricating bulk YBa.sub.2 Cu.sub.3 O.sub.x where compressed powder oxides and/or carbonates of Y and Ba and Cu present in mole ratios to form YBa.sub.2 Cu.sub.3 O.sub.x are heated in the presence of a Nd.sub.1+x Ba.sub.2-x Cu.sub.3 O.sub.y seed crystal to a temperature sufficient to form a liquid phase in the YBa.sub.2 Cu.sub.3 O.sub.x while maintaining the seed crystal solid. The materials are slowly cooled to provide a YBa.sub.2 Cu.sub.3 O.sub.x material having a predetermined number of domains between 1 and 5. Crack-free single domain materials can be formed using either plate shaped seed crystals or cube shaped seed crystals with a pedestal of preferential orientation material.

  16. Oxygen diffusion in single crystal barium titanate.

    PubMed

    Kessel, Markus; De Souza, Roger A; Martin, Manfred

    2015-05-21

    Oxygen diffusion in cubic, nominally undoped, (100) oriented BaTiO3 single crystals has been studied by means of (18)O2/(16)O2 isotope exchange annealing and subsequent determination of the isotope profiles in the solid by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Experiments were carried out as a function of temperature 973 < T/K < 1173, at an oxygen activity of aO2 = 0.200, and as a function of oxygen activity 0.009 < aO2 < 0.900 at T = 1073 K. The oxygen isotope profiles comprise two parts: slow diffusion through a space-charge zone at the surface depleted of oxygen vacancies followed by faster diffusion in a homogeneous bulk phase. The entire isotope profile can be described by a single solution to the diffusion equation involving only three fitting parameters: the surface exchange coefficient ks*, the space-charge potential Φ0 and the bulk diffusion coefficient D*(∞). Analysis of the temperature and oxygen activity dependencies of D*(∞) and Φ0 yields a consistent picture of both the bulk and the interfacial defect chemistry of BaTiO3. Values of the oxygen vacancy diffusion coefficient DV extracted from measured D*(∞) data are compared with literature data; consequently a global expression for the vacancy diffusivity in BaTiO3 for the temperature range 466 < T/K < 1273 is obtained, with an activation enthalpy of vacancy migration, ΔHmig,V = (0.70 ± 0.04) eV.

  17. Fabrication of polypyrrole nano-arrays in lysozyme single crystals

    NASA Astrophysics Data System (ADS)

    England, Matt W.; Lambert, Elizabeth M.; Li, Mei; Turyanska, Lyudmila; Patil, Avinash J.; Mann, Stephen

    2012-10-01

    A template-directed method for the synthesis and organization of partially oxidized polypyrrole (PPy) nanoscale arrays within the solvent channels of glutaraldehyde-cross-linked lysozyme single crystals is presented. Macroscopic single crystals of the periodically arranged protein-polymer superstructure are electrically conductive, insoluble in water and organic solvents, and display increased levels of mechanical plasticity compared with native cross-linked lysozyme crystals.A template-directed method for the synthesis and organization of partially oxidized polypyrrole (PPy) nanoscale arrays within the solvent channels of glutaraldehyde-cross-linked lysozyme single crystals is presented. Macroscopic single crystals of the periodically arranged protein-polymer superstructure are electrically conductive, insoluble in water and organic solvents, and display increased levels of mechanical plasticity compared with native cross-linked lysozyme crystals. Electronic supplementary information (ESI) available: Optical microscopy, SEM, TEM images, FTIR spectra and tables, conductivity plot. Experimental methods. See DOI: 10.1039/c2nr32413j

  18. Giant rotating magnetocaloric effect in RNi5 single crystals

    NASA Astrophysics Data System (ADS)

    de Oliveira, N. A.

    2017-04-01

    In this paper we theoretically discuss the rotating magnetocaloric effect in RNi5 (R = Nd , Tb , Dy , Er) single crystals, by using a model of interacting magnetic moments including the interaction with the crystal electric field. Our theoretical calculations show that the rotating magnetocaloric effect in RNi5 single crystals is as large as the conventional one. This fact points out that these single crystals are also good candidates to be used in magnetic refrigerators working at low temperatures and based on the rotating magnetocaloric effect.

  19. Microscale Laser Peen Forming of Single Crystal

    SciTech Connect

    Wang,Y.; Fan, Y.; Kysar, J.; Vukelic, S.; Yao, Y.

    2008-01-01

    As the result of quickly increased requirement in many industrial products resulting from microtechnology, laser thermal microforming and microsurface treatment [microscale laser shock peening (?LSP)] have been well studied. By combining the beneficial effects of these two processes with a controlled bending deformation, microscale laser peen forming (?LPF) attracts more attention recently since it not only improves the fatigue life of the material but also shapes microscale metallic parts at the same time. In the present study, ?LSP of single crystal aluminum was presented to study anisotropic material response. Local plastic deformation was characterized by lattice rotation measured through electron backscatter diffraction. Residual stress distributions of both sides of a peened sample, characterized by x-ray microdiffraction, were compared with the results obtained from finite element method simulation. ?LPF anisotropic behavior was investigated in three effective slip systems via both the anisotropic slip line theory and numerical method. Also, the work hardening effect resulted from self-hardening, and latent hardening was analyzed through comparing the results with and without considering hardening.

  20. Excitonic polaritons of zinc diarsenide single crystals

    NASA Astrophysics Data System (ADS)

    Syrbu, N. N.; Stamov, I. G.; Zalamai, V. V.; Dorogan, A.

    2017-02-01

    Excitonic polaritons of ZnAs2 single crystals had been investigated. Parameters of singlet excitons with D2bar(z) symmetry and orthoexcitons 2D1bar(y)+D2bar(x) had been determined. Spectral dependencies of ordinary and extraordinary dispersion of refractive index had been calculated using interferential reflection and transmittance spectra. It was shown, that A excitonic series were due to hole (V1) and electron (C1) bands. The values of effective masses of electrons (mc*=0.10 m0) and holes (mv1*=0.89 m0) had been estimated. It was revealed that the hole mass mv1* changes from 1.03 m0 to 0.55 m0 at temperature increasing from 10 K up to 230 K and that the electron mass mc* does not depend on temperature. The integral absorption A (eV cm-1) of the states n=1, 2 and 3 of D2bar(z) excitons depends on the An≈n-3 equality, which it is characteristic for S-type excitonic functions. Temperature dependences of the integral absorption of ground states for D2bar(z) and D2bar(D) excitons differ. The ground states of B and C excitons formed by V3 - C1 and V4 - C1 bands and its parameters had been determined.

  1. Advanced single crystal for SSME turbopumps

    NASA Technical Reports Server (NTRS)

    Fritzemeier, L. G.

    1989-01-01

    The objective of this program was to evaluate the influence of high thermal gradient casting, hot isostatic pressing (HIP) and alternate heat treatments on the microstructure and mechanical properties of a single crystal nickel base superalloy. The alloy chosen for the study was PWA 1480, a well characterized, commercial alloy which had previously been chosen as a candidate for the Space Shuttle Main Engine high pressure turbopump turbine blades. Microstructural characterization evaluated the influence of casting thermal gradient on dendrite arm spacing, casting porosity distribution and alloy homogeneity. Hot isostatic pressing was evaluated as a means of eliminating porosity as a preferred fatigue crack initiation site. The alternate heat treatment was chosen to improve hydrogen environment embrittlement resistance and for potential fatigue life improvement. Mechanical property evaluation was aimed primarily at determining improvements in low cycle and high cycle fatigue life due to the advanced processing methods. Statistically significant numbers of tests were conducted to quantitatively demonstrate life differences. High thermal gradient casting improves as-cast homogeneity, which facilitates solution heat treatment of PWA 1480 and provides a decrease in internal pore size, leading to increases in low cycle and high cycle fatigue lives.

  2. Multibit ferroelectric field-effect transistor with epitaxial-like Pb(Zr,Ti)O3

    NASA Astrophysics Data System (ADS)

    Park, Jae Hyo; Kim, Hyung Yoon; Seok, Ki Hwan; Kiaee, Zohreh; Lee, Sol Kyu; Joo, Seung Ki

    2016-03-01

    Being able to control grain boundaries during the phase transformation when processing a ferroelectric thin-film is crucial for the successful development of practical multibit ferroelectric memory. A novel development of ferroelectric thin-film crystallization processing for realizing epitaxial-like single crystals via artificial nucleation by Pt-seeding is reported here. Dividing the nucleation and growth mechanism by Pt-seeding, it is possible to obtain large and uniform rectangular-shaped ferroelectric grains, large enough to fabricate a field-effect transistor (FET) in the inside of the crystal grain. The fabricated ferroelectric FET, Pt/Pb(Zr,Ti)O3/ZrTiO4/Si, showed a large memory window (˜2.2 V), a low operation voltage (˜6 V), and an ultra-fast program/erase speed (˜10-6 s). Moreover, there was no degradation after 1015 cycles of bipolar fatigue testing and the sample even showed a long retention time after 1 yr. All of these characteristics correspond to the best performance among all types of ferroelectric field-effect transistors reported thus far.

  3. Single crystal micromechanical resonator and fabrication methods thereof

    DOEpatents

    Olsson, Roy H.; Friedmann, Thomas A.; Homeijer, Sara Jensen; Wiwi, Michael; Hattar, Khalid Mikhiel; Clark, Blythe; Bauer, Todd; Van Deusen, Stuart B.

    2016-12-20

    The present invention relates to a single crystal micromechanical resonator. In particular, the resonator includes a lithium niobate or lithium tantalate suspended plate. Also provided are improved microfabrication methods of making resonators, which does not rely on complicated wafer bonding, layer fracturing, and mechanical polishing steps. Rather, the methods allow the resonator and its components to be formed from a single crystal.

  4. A Quick Method for Determining the Density of Single Crystals.

    ERIC Educational Resources Information Center

    Roman, Pascual; Gutierrez-Zorrilla, Juan M.

    1985-01-01

    Shows how the Archimedes method is used to determine the density of a single crystal of ammonium oxalate monohydrate. Also shows how to calculate the density of other chemicals when they are available as single crystals. Experimental procedures and materials needed are included. (JN)

  5. Mercuric iodide single crystals for nuclear radiation detectors

    SciTech Connect

    Li, W.; Li, Z.; Zhu, S.; Yin, S.; Zhao, B.; Chen, G.; Yin, S.; Yuan, H.; Xu, H.

    1996-06-01

    Large size HgI{sub 2} single crystals were grown using the Modified Temperature Oscillation Method (MTOM) with low dislocation densities in a relatively stable temperature environment. Radiation detectors were fabricated from the single crystals which showed good energy resolution with small polarization. Applications have been found in geological explorations, marine mineral analysis, environment pollution monitoring, industrial material quality assurance, and space explorations.

  6. Semiconductor single crystal external ring resonator cavity laser and gyroscope

    SciTech Connect

    Spitzer, M.P.

    1993-08-31

    A ring laser is described comprising: a semiconductor single crystal external ring resonator cavity having a plurality of reflecting surfaces defined by the planes of the crystal and establishing a closed optical path; and a discrete laser medium disposed in said semiconductor single crystal external ring resonator cavity for generating coherent light in said cavity, wherein said resonator cavity is decoupled from the laser medium.

  7. Magnetic and magnetoelectric properties of Ba2-xSrxNi2Fe12O22 single crystals with Y-type hexaferrite structure

    NASA Astrophysics Data System (ADS)

    Hiraoka, Yuji; Nakamura, Hiroyuki; Soda, Minoru; Wakabayashi, Yusuke; Kimura, Tsuyoshi

    2011-08-01

    We studied the magnetic and magnetoelectric properties of Ba2-xSrxNi2Fe12O22 single crystals over a wide composition range (0 ≤ x ≤ 1.5). All the crystals show a ferrimagnetic order at around 660 K. While a Sr-free crystal is simply ferrimagnetic down to the lowest temperature, a transition from the ferrimagnetic into a screw magnetic ordered state was observed at temperatures below 300 K in Sr-substituted crystals. The transition temperature monotonically increases with increasing Sr content, meaning that the screw ordered state is stabilized by the Sr-substitution. By applying a magnetic field perpendicular to the hexagonal c axis, the samples showing the ground-state screw order undergo successive metamagnetic transitions and exhibit magnetically induced ferroelectricity in some of the intermediate magnetic phases. In an intermediate magnetic phase, the largest electric polarization emerges (2 × 102 μC/m2 for x = 1.5 crystal), i.e., magnetoelectric effect. The evolution of the magnetic structures related to the magnetoelectric effect in x = 1.5 crystal was clarified by means of in-field neutron diffraction measurements. Though the magnetoelectric effect in the as-grown crystal was measurable only below ˜100 K due to its low resistivity, a post-annealing drastically enhances the resistivity and allows us to observe the magnetically induced ferroelectricity up to ˜175 K.

  8. Role of curvature elasticity in sectorization and ripple formation during melt crystallization of polymer single crystals.

    PubMed

    Mehta, Rujul; Keawwattana, Wirunya; Guenthner, Andrew L; Kyu, Thein

    2004-06-01

    The present article focuses on theoretical elucidation of possible effect of mechanical deformation on spatio-temporal emergence of unusual polymer morphology subjected to quiescent isothermal crystallization conditions. The present theory developed is based on a phase field model consisted of non-conserved time dependent Ginzburg-Landau equation having an asymmetric double well potential in the crystal order parameter signifying metastability for crystallization, coupled with the chain tilt angle involving curvature elasticity and strain recovery potentials. Under quiescent crystallization conditions, the curvature elasticity term is needed to discern the emergence of sectorized single crystals. Upon coupling with the strain recovery potential, the numerical calculation captures ripple formation running across the long lamellar growth front, which may be attributed to lamellar buckling caused by the volume shrinkage. Of particular interest is that these simulated topologies of the single crystals are in good accord with the growth character of syndiotactic polypropylene single crystals observed experimentally by us during isothermal crystallization from the melt.

  9. Study of single crystals of metal solid solutions

    NASA Technical Reports Server (NTRS)

    Doty, J. P.; Reising, J. A.

    1973-01-01

    The growth of single crystals of relatively high melting point metals such as silver, copper, gold, and their alloys was investigated. The purpose was to develop background information necessary to support a space flight experiment and to generate ground based data for comparison. The ground based data, when compared to the data from space grown crystals, are intended to identify any effects which zero-gravity might have on the basic process of single crystal growth of these metals. The ultimate purposes of the complete investigation are to: (1) determine specific metals and alloys to be investigated; (2) grow single metal crystals in a terrestrial laboratory; (3) determine crystal characteristics, properties, and growth parameters that will be effected by zero-gravity; (4) evaluate terrestrially grown crystals; (5) grow single metal crystals in a space laboratory such as Skylab; (6) evaluate the space grown crystals; (7) compare for zero-gravity effects of crystal characteristics, properties, and parameters; and (8) make a recommendation as to production of these crystals as a routine space manufacturing proceses.

  10. Segmentation Effect on Inhomogeneity of [110]-Single Crystal Deformation

    NASA Astrophysics Data System (ADS)

    Lychagin, D. V.; Nesterenko, E. A. Alfyorova V. P.

    2016-08-01

    This work presents a detailed analysis of segmentation process in FCC single crystals with compression axis [110] and side faces( ̅110) and (001) considering effect of octahedral shear crystal-geometry and basic stress concentrators. Sequence of meso-band systems formation on side faces is determined. Macro-segmentation patterns are specified, that are common to the FCC single crystals under investigation. It is proved that rectangular shape of highly compressed crystals, elongated in direction of operating planes, is conditioned by orientation symmetry of compression axis, single crystal side faces and shears directions, which are characteristic for the given orientation. The specified patterns are characteristic only for the samples with initial height-to-width ratio equal to 2. When varying sample height relative to the initial one, segmentation patterns will also vary due to crystal geometry variations.

  11. Modified triglycine sulphate (TGS) single crystals for pyroelectric infrared detector applications

    NASA Technical Reports Server (NTRS)

    Banan, M.; Lal, R. B.; Batra, Ashok

    1992-01-01

    Effects of caesium and cerium, L-alanine, and caesium plus L-alanine impurities on ferroelectric and pyroelectric properties of TGS crystals are investigated. Dielectric constant and loss, pyroelectric coefficient, spontaneous polarization, and coercive field measurements of these modified crystals, as a function of temperature, are reported. Caesium and cerium did not affect the electrical properties of TGS crystals significantly, whereas L-alanine- and, especially, Cs + L-alanine-doped TGS crystals exhibited promising improvements in pyroelectric properties, up to 48 C, as compared to pure TGS crystals.

  12. Growth dynamics of isotactic polypropylene single crystals during isothermal crystallization from a miscible polymeric solvent.

    PubMed

    Mehta, Rujul; Keawwattana, Wirunya; Kyu, Thein

    2004-02-22

    The present article presents a spatiotemporal growth of isotactic polypropylene (iPP) single crystals, melt crystallized from a polymeric solvent, i.e., poly (ethylene octene) copolymer that is known to be miscible with iPP. Optical and atomic force microscopic investigations reveal that the melt grown single crystals of iPP develop in the form of two parallel rows of crystal lamellae, but these crystals merge at the tips. To elucidate the mechanism of these emerging parallel rows of iPP crystals, a phase field model pertaining to solidification phenomena has been employed that involves a nonconserved crystal order parameter and a chain-tilting angle. This phase field model is based on the free energy of crystallization, having an asymmetric double well, and a tensorial surface free energy of the crystal interface coupled with a curvature elastic free energy that is possessed by the solid-liquid interface. The spatiotemporal simulation of iPP single crystal growth has been carried out on a square lattice based on the finite difference method for spatial steps and an explicit method for temporal steps with a periodic boundary condition. The appearance of the seemingly twin crystal is captured in the simulation, which may be attributed to the sector demarcation that is taking place in the anisotropically growing single crystal of iPP.

  13. Growth dynamics of isotactic polypropylene single crystals during isothermal crystallization from a miscible polymeric solvent

    NASA Astrophysics Data System (ADS)

    Mehta, Rujul; Keawwattana, Wirunya; Kyu, Thein

    2004-02-01

    The present article presents a spatiotemporal growth of isotactic polypropylene (iPP) single crystals, melt crystallized from a polymeric solvent, i.e., poly (ethylene octene) copolymer that is known to be miscible with iPP. Optical and atomic force microscopic investigations reveal that the melt grown single crystals of iPP develop in the form of two parallel rows of crystal lamellae, but these crystals merge at the tips. To elucidate the mechanism of these emerging parallel rows of iPP crystals, a phase field model pertaining to solidification phenomena has been employed that involves a nonconserved crystal order parameter and a chain-tilting angle. This phase field model is based on the free energy of crystallization, having an asymmetric double well, and a tensorial surface free energy of the crystal interface coupled with a curvature elastic free energy that is possessed by the solid-liquid interface. The spatiotemporal simulation of iPP single crystal growth has been carried out on a square lattice based on the finite difference method for spatial steps and an explicit method for temporal steps with a periodic boundary condition. The appearance of the seemingly twin crystal is captured in the simulation, which may be attributed to the sector demarcation that is taking place in the anisotropically growing single crystal of iPP.

  14. Method for harvesting rare earth barium copper oxide single crystals

    DOEpatents

    Todt, Volker R.; Sengupta, Suvankar; Shi, Donglu

    1996-01-01

    A method of preparing high temperature superconductor single crystals. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals of the high temperature superconductor, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals of the high temperature superconductor on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals melted, allowing the wicking away of the peritectic liquid.

  15. Method for harvesting single crystals from a peritectic melt

    DOEpatents

    Todt, V.R.; Sengupta, S.; Shi, D.

    1996-08-27

    A method of preparing single crystals is disclosed. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals unmelted, allowing the wicking away of the peritectic liquid. 2 figs.

  16. Method for harvesting single crystals from a peritectic melt

    DOEpatents

    Todt, Volker R.; Sengupta, Suvankar; Shi, Donglu

    1996-01-01

    A method of preparing single crystals. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals unmelted, allowing the wicking away of the peritectic liquid.

  17. Stability of Detached Grown Germanium Single Crystals

    NASA Technical Reports Server (NTRS)

    Schweizer, M.; Volz, M. P.; Cobb, S. D.; Vujisic, L.; Szofran, F. R.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Detachment of the melt meniscus from the crucible during semiconductor Bridgman growth experiments has been observed in recent years, especially under microgravity experiments. Under earth conditions, the hydrostatic pressure counteracts the mechanism, whereby it is more difficult to achieve detached Bridgman growth. Attempts to get stable detached growth under terrestrial conditions have been discussed in the literature and have been the subject of recent experiments in our own group. The advantage of crystals grown without wall contact is obvious: In general, they possess a higher crystal quality than conventional Bridgman grown crystals with wall contact. However, due to the interaction of different parameters such as the wetting behavior of the melt with the crucible, and the dependence of the growth angle with the shape of the melt meniscus, the mechanism leading to detachment is very complicated and not completely understood. We have grown several doped and undoped Germanium crystals with the detached Bridgman and the normal Bridgman growth technique. Pyrolytic boron nitride containers were used for all growth experiments. In the detached grown crystals the typical gap thickness between the pBN crucible and the crystal is in the range of 10 to 100 micrometers, which was determined by performing profilometer measurements. Etch pit density measurements were also performed and a comparison between detached and attached grown crystals will be given. An interesting feature was detected on the surface of a detached grown crystal. Strong surface striations with an average axial distance of 0.5 mm were observed around the whole circumference. The maximum fluctuation of the gap thickness is in the range of 5-10 micrometers. These variations of the detached gap along the crystal axis can be explained by a kind of stiction of the melt/crucible interface and thus by a variation of the meniscus shape. This phenomenon leading to the fluctuation of the gap thickness will be

  18. Stability of Detached Grown Germanium Single Crystals

    NASA Technical Reports Server (NTRS)

    Schweizer, M.; Volz, M. P.; Cobb, S. D.; Motakef, S.; Szofran, F. R.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    Detachment of the melt meniscus from the crucible during semiconductor Bridgman growth experiments has been observed in recent years especially, under microgravity experiments. Under earth conditions, the hydrostatic pressure counteracts the mechanism, whereby it is more difficult to achieve detached Bridgman growth. Attempts to get stable detached growth under terrestrial conditions have been discussed in the literature and have been the subject of recent experiments in our own group. The advantage of crystals grown without wall contact is obvious: In general, they possess a higher crystal quality than conventional Bridgman grown crystals with wall contact. However, due to the interaction of different parameters such as the wetting behavior of the melt with the crucible, and the dependence of the growth angle with the shape of the melt meniscus, the mechanism leading to detachment is very complicated and not completely understood. We have grown several doped and undoped Germanium crystals with the detached Bridgman and the normal Bridgman growth technique. Pyrolytic boron nitride containers were used for all growth experiments. In the detached grown crystals the typical gap thickness between the pBN crucible and the crystal is in the range of 10 to 100 microns, which was determined by performing profilometer measurements. Etch pit density measurements were also performed and a comparison between detached and attached grown crystals will be given. An interesting feature was detected on the surface of a detached grown crystal. Strong surface striations with an average axial distance of 0.5mm were observed around the whole circumference. The maximum fluctuation of the gap thickness is in the range of 5-10 microns. These variations of the detached gap along the crystal axis can be explained by a kind of stiction of the melt/crucible interface and thus by a variation of the meniscus shape. This phenomenon leading to the fluctuation of the gap thickness will be

  19. Incipient ferroelectricity of water molecules confined to nano-channels of beryl

    PubMed Central

    Gorshunov, B. P.; Torgashev, V. I.; Zhukova, E. S.; Thomas, V. G.; Belyanchikov, M. A.; Kadlec, C.; Kadlec, F.; Savinov, M.; Ostapchuk, T.; Petzelt, J.; Prokleška, J.; Tomas, P. V.; Pestrjakov, E. V.; Fursenko, D. A.; Shakurov, G. S.; Prokhorov, A. S.; Gorelik, V. S.; Kadyrov, L. S.; Uskov, V. V.; Kremer, R. K.; Dressel, M.

    2016-01-01

    Water is characterized by large molecular electric dipole moments and strong interactions between molecules; however, hydrogen bonds screen the dipole–dipole coupling and suppress the ferroelectric order. The situation changes drastically when water is confined: in this case ordering of the molecular dipoles has been predicted, but never unambiguously detected experimentally. In the present study we place separate H2O molecules in the structural channels of a beryl single crystal so that they are located far enough to prevent hydrogen bonding, but close enough to keep the dipole–dipole interaction, resulting in incipient ferroelectricity in the water molecular subsystem. We observe a ferroelectric soft mode that causes Curie–Weiss behaviour of the static permittivity, which saturates below 10 K due to quantum fluctuations. The ferroelectricity of water molecules may play a key role in the functioning of biological systems and find applications in fuel and memory cells, light emitters and other nanoscale electronic devices. PMID:27687693

  20. Incipient ferroelectricity of water molecules confined to nano-channels of beryl

    NASA Astrophysics Data System (ADS)

    Gorshunov, B. P.; Torgashev, V. I.; Zhukova, E. S.; Thomas, V. G.; Belyanchikov, M. A.; Kadlec, C.; Kadlec, F.; Savinov, M.; Ostapchuk, T.; Petzelt, J.; Prokleška, J.; Tomas, P. V.; Pestrjakov, E. V.; Fursenko, D. A.; Shakurov, G. S.; Prokhorov, A. S.; Gorelik, V. S.; Kadyrov, L. S.; Uskov, V. V.; Kremer, R. K.; Dressel, M.

    2016-09-01

    Water is characterized by large molecular electric dipole moments and strong interactions between molecules; however, hydrogen bonds screen the dipole-dipole coupling and suppress the ferroelectric order. The situation changes drastically when water is confined: in this case ordering of the molecular dipoles has been predicted, but never unambiguously detected experimentally. In the present study we place separate H2O molecules in the structural channels of a beryl single crystal so that they are located far enough to prevent hydrogen bonding, but close enough to keep the dipole-dipole interaction, resulting in incipient ferroelectricity in the water molecular subsystem. We observe a ferroelectric soft mode that causes Curie-Weiss behaviour of the static permittivity, which saturates below 10 K due to quantum fluctuations. The ferroelectricity of water molecules may play a key role in the functioning of biological systems and find applications in fuel and memory cells, light emitters and other nanoscale electronic devices.

  1. Incipient ferroelectricity of water molecules confined to nano-channels of beryl.

    PubMed

    Gorshunov, B P; Torgashev, V I; Zhukova, E S; Thomas, V G; Belyanchikov, M A; Kadlec, C; Kadlec, F; Savinov, M; Ostapchuk, T; Petzelt, J; Prokleška, J; Tomas, P V; Pestrjakov, E V; Fursenko, D A; Shakurov, G S; Prokhorov, A S; Gorelik, V S; Kadyrov, L S; Uskov, V V; Kremer, R K; Dressel, M

    2016-09-30

    Water is characterized by large molecular electric dipole moments and strong interactions between molecules; however, hydrogen bonds screen the dipole-dipole coupling and suppress the ferroelectric order. The situation changes drastically when water is confined: in this case ordering of the molecular dipoles has been predicted, but never unambiguously detected experimentally. In the present study we place separate H2O molecules in the structural channels of a beryl single crystal so that they are located far enough to prevent hydrogen bonding, but close enough to keep the dipole-dipole interaction, resulting in incipient ferroelectricity in the water molecular subsystem. We observe a ferroelectric soft mode that causes Curie-Weiss behaviour of the static permittivity, which saturates below 10 K due to quantum fluctuations. The ferroelectricity of water molecules may play a key role in the functioning of biological systems and find applications in fuel and memory cells, light emitters and other nanoscale electronic devices.

  2. The Growth of Large Single Crystals.

    ERIC Educational Resources Information Center

    Baer, Carl D.

    1990-01-01

    Presented is an experiment which demonstrates principles of experimental design, solubility, and crystal growth and structure. Materials, procedures and results are discussed. Suggestions for adapting this activity to the high school laboratory are provided. (CW)

  3. Barium iodide single-crystal scintillator detectors

    NASA Astrophysics Data System (ADS)

    Cherepy, Nerine J.; Hull, Giulia; Niedermayr, Thomas R.; Drobshoff, Alexander; Payne, Stephen A.; Roy, Utpal N.; Cui, Yunlong; Bhattacharaya, Ajanta; Harrison, Melissa; Guo, Mingsheng; Groza, Michael; Burger, Arnold

    2007-09-01

    We find that the high-Z crystal Barium Iodide is readily growable by the Bridgman growth technique and is less prone to crack compared to Lanthanum Halides. We have grown Barium Iodide crystals: undoped, doped with Ce 3+, and doped with Eu 2+. Radioluminescence spectra and time-resolved decay were measured. BaI II(Eu) exhibits luminescence from both Eu 2+ at 420 nm (~450 ns decay), and a broad band at 550 nm (~3 μs decay) that we assign to a trapped exciton. The 550 nm luminescence decreases relative to the Eu 2+ luminescence when the Barium Iodide is zone refined prior to crystal growth. We also describe the performance of BaI II(Eu) crystals in experimental scintillator detectors.

  4. A study of crystal growth by solution technique. [triglycine sulfate single crystals

    NASA Technical Reports Server (NTRS)

    Lal, R. B.

    1979-01-01

    The advantages and mechanisms of crystal growth from solution are discussed as well as the effects of impurity adsorption on the kinetics of crystal growth. Uncertainities regarding crystal growth in a low gravity environment are examined. Single crystals of triglycine sulfate were grown using a low temperature solution technique. Small components were assembled and fabricated for future space flights. A space processing experiment proposal accepted by NASA for the Spacelab-3 mission is included.

  5. Physicochemical principles of high-temperature crystallization and single crystal growth methods

    NASA Astrophysics Data System (ADS)

    Bagdasarov, Kh. S.

    The mechanisms of crystal growth are reviewed, with attention given to the physicochemical reactions taking place in the melt near the phase boundary; phenomena determining physical and chemical kinetics directly at the growth front; solid-phase processes occurring within the crystal. Methods for growing refractory single crystals are discussed with particular reference to the Verneuil method, zone melting, Czhochralskii growth, horizontal directional solidification, and the Stockbarger method. Methods for growing crystals of complex geometrical shapes are also discussed.

  6. Growing Single Crystals of Compound Semiconductors

    NASA Technical Reports Server (NTRS)

    Naumann, Robert J.; Lehoczky, Sandor L.; Frazier, Donald O.

    1987-01-01

    Defect reduced by preventing melt/furnace contact and suppressing convention. Large crystals of compound semiconductors with few defects grown by proposed new method. Such materials as gallium arsenide and cadmium telluride produced, with quality suitable for very-large-scale integrated circuits or for large focal-plane arrays of photodetectors. Method used on small scale in Earth gravity, but needs microgravity to provide crystals large enough for industrial use.

  7. Single-drop optimization of protein crystallization.

    PubMed

    Meyer, Arne; Dierks, Karsten; Hilterhaus, Dierk; Klupsch, Thomas; Mühlig, Peter; Kleesiek, Jens; Schöpflin, Robert; Einspahr, Howard; Hilgenfeld, Rolf; Betzel, Christian

    2012-08-01

    A completely new crystal-growth device has been developed that permits charting a course across the phase diagram to produce crystalline samples optimized for diffraction experiments. The utility of the device is demonstrated for the production of crystals for the traditional X-ray diffraction data-collection experiment, of microcrystals optimal for data-collection experiments at a modern microbeam insertion-device synchrotron beamline and of nanocrystals required for data collection on an X-ray laser beamline.

  8. Single-drop optimization of protein crystallization

    PubMed Central

    Meyer, Arne; Dierks, Karsten; Hilterhaus, Dierk; Klupsch, Thomas; Mühlig, Peter; Kleesiek, Jens; Schöpflin, Robert; Einspahr, Howard; Hilgenfeld, Rolf; Betzel, Christian

    2012-01-01

    A completely new crystal-growth device has been developed that permits charting a course across the phase diagram to produce crystalline samples optimized for diffraction experiments. The utility of the device is demonstrated for the production of crystals for the traditional X-ray diffraction data-collection experiment, of microcrystals optimal for data-collection experiments at a modern microbeam insertion-device synchrotron beamline and of nanocrystals required for data collection on an X-ray laser beamline. PMID:22869140

  9. A Single Crystal Niobium RF Cavity of the TESLA Shape

    SciTech Connect

    Singer, W.; Singer, X.; Kneisel, P.

    2007-08-09

    A fabrication method for single crystal niobium cavities of the TESLA shape was proposed on the basis of metallographic investigations and electron beam welding tests on niobium single crystals. These tests showed that a cavity can be produced without grain boundaries even in the welding area. An appropriate annealing allows the outgassing of hydrogen and stress relaxation of the material without destruction of the single crystal. A prototype single crystal single cell cavity was build. An accelerating gradient of 37.5 MV/m was reached after approximately 110 {mu}m of Buffered Chemical Polishing (BCP) and in situ baking at 120 deg. C for 6 hrs with a quality factor exceeding 2x1010 at 1.8 K. The developed fabrication method can be extended to fabrication of multi cell cavities.

  10. A Single Crystal Niobium RF Cavity of the TESLA Shape

    SciTech Connect

    W. Singer; X. Singer; P. Kneisel

    2007-09-01

    A fabrication method for single crystal niobium cavities of the TESLA shape was proposed on the basis of metallographic investigations and electron beam welding tests on niobium single crystals. These tests showed that a cavity can be produced without grain boundaries even in the welding area. An appropriate annealing allows the outgassing of hydrogen and stress relaxation of the material without destruction of the single crystal. A prototype single crystal single cell cavity was built. An accelerating gradient of 37.5 MV/m was reached after approximately 110 mu-m of Buffered Chanical Polishing (BCP) and in situ baking at 120°C for 6 hrs with a quality factor exceeding 2x1010 at 1.8 K. The developed fabrication method can be extended to fabrication of multi cell cavities.

  11. Pathways towards ferroelectricity in hafnia

    NASA Astrophysics Data System (ADS)

    Huan, Tran Doan; Sharma, Vinit; Rossetti, George A.; Ramprasad, Rampi

    2014-08-01

    The question of whether one can systematically identify (previously unknown) ferroelectric phases of a given material is addressed, taking hafnia (HfO2) as an example. Low free energy phases at various pressures and temperatures are identified using a first-principles based structure search algorithm. Ferroelectric phases are then recognized by exploiting group theoretical principles for the symmetry-allowed displacive transitions between nonpolar and polar phases. Two orthorhombic polar phases occurring in space groups Pca21 and Pmn21 are singled out as the most viable ferroelectric phases of hafnia, as they display low free energies (relative to known nonpolar phases), and substantial switchable spontaneous electric polarization. These results provide an explanation for the recently observed surprising ferroelectric behavior of hafnia, and reveal pathways for stabilizing ferroelectric phases of hafnia as well as other compounds.

  12. Growth and characterization of diammonium copper disulphate hexahydrate single crystal

    SciTech Connect

    Siva Sankari, R.; Perumal, Rajesh Narayana

    2014-03-01

    Graphical abstract: Diammonium copper disulphate hexahydrate (DACS) is one of the most promising inorganic dielectric crystals with exceptional mechanical properties. Good quality crystals of DACS were grown by using solution method in a period of 30 days. The grown crystals were subjected to single crystal X-ray diffraction analysis in order to establish their crystalline nature. Thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis were performed for the crystal. Several solid state physical parameters have been determined for the grown crystals. The dielectric constant and the dielectric loss and AC conductivity of the grown crystal were studied as a function of frequency and temperature has been calculated and plotted. - Highlights: • Diammonium copper disulphate is grown for the first time and CCDC number obtained. • Thermal analysis is done to see the stability range of the crystals. • Band gap and UV cut off wavelength of the crystal are determined to be 2.4 eV and 472.86 nm, respectively. • Dielectric constant, dielectric loss and AC conductivity are plotted as a function of applied field. - Abstract: Diammonium copper disulphate hexahydrate is one of the most promising inorganic crystals with exceptional dielectric properties. A good quality crystal was harvested in a 30-day period using solution growth method. The grown crystal was subjected to various characterization techniques like single crystal X-ray diffraction analysis, thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis. Unit cell dimensions of the grown crystal have been identified from XRD studies. Functional groups of the title compounds have been identified from FTIR studies. Thermal stability of the samples was checked by TG/DTA studies. Band gap of the crystal was calculated. The dielectric constant and dielectric loss were studied as a function of frequency of the applied field. AC conductivity was plotted as a function

  13. Tip-induced domain growth on the non-polar cuts of lithium niobate single-crystals

    SciTech Connect

    Alikin, Denis O.; Ievlev, Anton; Turigin, Anton P.; Lobov, Alexei; Kalinin, Sergei V; Shur, Vladimir Ya.

    2015-05-05

    Currently ferroelectric materials with designed domain structures are considered as a perspective material for new generation of photonic, data storage and data processing devices. Application of external electric field is the most convenient way of the domain structure formation. Lots of papers are devoted to investigation of the domain kinetics on polar surface of crystals while the forward growth remains one of the most mysterious stages due to lack of experimental methods allowing to study it. Here we performed tip-induced polarization reversal on X- and Y-non-polar cuts in single-crystal of congruent lithium niobate allows us to study the forward growth with high spatial resolution. The revealed difference in the shape and length of domains induced on X- and Y-cuts is beyond previously developed theoretical approaches used for the theoretical consideration of the domains growth at non-polar ferroelectric surfaces. Lastly, to explain experimental results we used kinetic approach with anisotropy of screening efficiency along different crystallographic directions.

  14. Tip-induced domain growth on the non-polar cuts of lithium niobate single-crystals

    DOE PAGES

    Alikin, Denis O.; Ievlev, Anton; Turigin, Anton P.; ...

    2015-05-05

    Currently ferroelectric materials with designed domain structures are considered as a perspective material for new generation of photonic, data storage and data processing devices. Application of external electric field is the most convenient way of the domain structure formation. Lots of papers are devoted to investigation of the domain kinetics on polar surface of crystals while the forward growth remains one of the most mysterious stages due to lack of experimental methods allowing to study it. Here we performed tip-induced polarization reversal on X- and Y-non-polar cuts in single-crystal of congruent lithium niobate allows us to study the forward growthmore » with high spatial resolution. The revealed difference in the shape and length of domains induced on X- and Y-cuts is beyond previously developed theoretical approaches used for the theoretical consideration of the domains growth at non-polar ferroelectric surfaces. Lastly, to explain experimental results we used kinetic approach with anisotropy of screening efficiency along different crystallographic directions.« less

  15. Single crystal Processing and magnetic properties of gadolinium nickel

    SciTech Connect

    Shreve, Andrew John

    2012-01-01

    GdNi is a rare earth intermetallic material that exhibits very interesting magnetic properties. Spontaneous magnetostriction occurs in GdNi at T{sub C}, on the order of 8000ppm strain along the c-axis and only until very recently the mechanism causing this giant magnetostriction was not understood. In order to learn more about the electronic and magnetic structure of GdNi, single crystals are required for anisotropic magnetic property measurements. Single crystal processing is quite challenging for GdNi though since the rare-earth transition-metal composition yields a very reactive intermetallic compound. Many crystal growth methods are pursued in this study including crucible free methods, precipitation growths, and specially developed Bridgman crucibles. A plasma-sprayed Gd2O3 W-backed Bridgman crucible was found to be the best means of GdNi single crystal processing. With a source of high-quality single crystals, many magnetization measurements were collected to reveal the magnetic structure of GdNi. Heat capacity and the magnetocaloric effect are also measured on a single crystal sample. The result is a thorough report on high quality single crystal processing and the magnetic properties of GdNi.

  16. Adaptive ferroelectric states in systems with low domain wall energy: Tetragonal microdomains

    NASA Astrophysics Data System (ADS)

    Jin, Y. M.; Wang, Y. U.; Khachaturyan, A. G.; Li, J. F.; Viehland, D.

    2003-09-01

    Ferroelectric and ferroelastic phases with very low domain wall energies have been shown to form miniaturized microdomain structures. A theory of an adaptive ferroelectric phase has been developed to predict the microdomain-averaged crystal lattice parameters of this structurally inhomogeneous state. The theory is an extension of conventional martensite theory, applied to ferroelectric systems with very low domain wall energies. The case of ferroelectric microdomains of tetragonal symmetry is considered. It is shown for such a case that a nanoscale coherent mixture of microdomains can be interpreted as an adaptive ferroelectric phase, whose microdomain-averaged crystal lattice is monoclinic. The crystal lattice parameters of this monoclinic phase are self-adjusting parameters, which minimize the transformation stress. Self-adjustment is achieved by application of the invariant plane strain to the parent cubic lattice, and the value of the self-adjusted parameters is a linear superposition of the lattice constants of the parent and product phases. Experimental investigations of Pb(Mg1/3Nb2/3)O3-PbTiO3 and Pb(Zn1/3Nb2/3)O3-PbTiO3 single crystals confirm many of the predictions of this theory.

  17. Conformal Domain Miniaturization and Adaptive Monoclinic (Pseudo-orthorhombic) Ferroelectric States

    NASA Astrophysics Data System (ADS)

    Jin, Y. M.; Wang, Yu; Khachaturyan, A. G.; Li, J. F.; Viehland, D.

    2003-08-01

    Ferroelectric and ferroelastic phases with very low domain wall energies have been shown to form miniaturized microdomain structures. A theory of an adaptive ferroelectric phase has been developed to predict the microdomain-averaged crystal lattice parameters of this structurally inhomogeneous state. The theory is an extension of conventional martensite theory, applied to ferroelectric systems with very low domain wall energies. The cases of ferroelectric microdomains of tetragonal (FEt) symmetry are considered. It is shown that a nano-scale coherent mixture of microdomains can be interpreted as an adaptive ferroelectric phase, whose microdomain-averaged crystal lattice is monoclinic. The crystal lattice parameters of this monoclinic phase are self-adjusting parameters, which minimize the transformation stress. Self-adjustment is achieved by application of the invariant plane strain (IPS) to the parent cubic lattice, and the value of the self-adjusted parameters constitutes a mixture of the lattice constants of the parent and product phases. Experimental investigations of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) and Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) single crystals confirm many of the predictions of this theory.

  18. Growing intermetallic single crystals using in situ decanting

    SciTech Connect

    Petrovic, Cedomir; Canfield, Paul; Mellen, Jonathan

    2012-05-16

    High temperature metallic solution growth is one of the most successful and versatile methods for single crystal growth, and is particularly suited for exploratory synthesis. The method commonly utilizes a centrifuge at room temperature and is very successful for the synthesis of single crystal phases that can be decanted from the liquid below the melting point of the silica ampoule. In this paper, we demonstrate the extension of this method that enables single crystal growth and flux decanting inside the furnace at temperatures above 1200°C. This not only extends the number of available metallic solvents that can be used in exploratory crystal growth but also can be particularly well suited for crystals that have a rather narrow exposed solidification surface in the equilibrium alloy phase diagram.

  19. Ferroelectrics based absorbing layers

    NASA Astrophysics Data System (ADS)

    Hao, Jianping; Sadaune, Véronique; Burgnies, Ludovic; Lippens, Didier

    2014-07-01

    We show that ferroelectrics-based periodic structure made of BaSrTiO3 (BST) cubes, arrayed onto a metal plate with a thin dielectric spacer film exhibit a dramatic enhancement of absorbance with value close to unity. The enhancement is found around the Mie magnetic resonance of the Ferroelectrics cubes with the backside metal layer stopping any transmitted waves. It also involves quasi-perfect impedance matching resulting in reflection suppression via simultaneous magnetic and electrical activities. In addition, it was shown numerically the existence of a periodicity optimum, which is explained from surface waves analysis along with trade-off between the resonance damping and the intrinsic loss of ferroelectrics cubes. An experimental verification in a hollow waveguide configuration with a good comparison with full-wave numerical modelling is at last reported by measuring the scattering parameters of single and dual BST cubes schemes pointing out coupling effects for densely packed structures.

  20. Towards multicaloric effect with ferroelectrics

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Zhang, Guangzu; Li, Qi; Bellaiche, Laurent; Scott, James F.; Dkhil, Brahim; Wang, Qing

    2016-12-01

    Utilizing thermal changes in solid-state materials strategically offers caloric-based alternatives to replace current vapor-compression technology. To make full use of multiple forms of the entropy and achieve higher efficiency for designs of cooling devices, the multicaloric effect appears as a cutting-edge concept encouraging researchers to search for multicaloric materials with outstanding caloric properties. Here we report the multicaloric effect in BaTi O3 single crystals driven simultaneously by mechanical and electric fields and described via a thermodynamic phenomenological model. It is found that the multicaloric behavior is mainly dominated by the mechanical field rather than the electric field, since the paraelectric-to-ferroelectric transition is more sensitive to mechanical field than to electric field. The use of uniaxial stress competes favorably with pressure due to its much higher caloric strength and negligible elastic thermal change. It is revealed that multicaloric response can be significantly larger than just the sum of mechanocaloric and electrocaloric effects in temperature regions far above the Curie temperature but cannot exceed this limit near the Curie temperature. Our results also show the advantage of the multicaloric effect over the mechanically mediated electrocaloric effect or electrically mediated mechanocaloric effect. Our findings therefore highlight the importance of ferroelectric materials to develop multicaloric cooling.

  1. Fabrication of graded index single crystal in glass

    PubMed Central

    Veenhuizen, Keith; McAnany, Sean; Nolan, Daniel; Aitken, Bruce; Dierolf, Volkmar; Jain, Himanshu

    2017-01-01

    Lithium niobate crystals were grown in 3D through localized heating by femtosecond laser irradiation deep inside 35Li2O-35Nb2O5-30SiO2 glass. Laser scanning speed and power density were systematically varied to control the crystal growth process and determine the optimal conditions for the formation of single crystal lines. EBSD measurements showed that, in principle, single crystals can be grown to unlimited lengths using optimal parameters. We successfully tuned the parameters to a growth mode where nucleation and growth occur upon heating and ahead of the scanning laser focus. This growth mode eliminates the problem reported in previous works of non-uniform polycrystallinity because of a separate growth mode where crystallization occurs during cooling behind the scanning laser focus. To our knowledge, this is the first report of such a growth mode using a fs laser. The crystal cross-sections possessed a symmetric, smooth lattice misorientation with respect to the c-axis orientation in the center of the crystal. Calculations indicate the observed misorientation leads to a decrease in the refractive index of the crystal line from the center moving outwards, opening the possibility to produce within glass a graded refractive index single crystal (GRISC) optically active waveguide. PMID:28287174

  2. Fabrication of graded index single crystal in glass

    NASA Astrophysics Data System (ADS)

    Veenhuizen, Keith; McAnany, Sean; Nolan, Daniel; Aitken, Bruce; Dierolf, Volkmar; Jain, Himanshu

    2017-03-01

    Lithium niobate crystals were grown in 3D through localized heating by femtosecond laser irradiation deep inside 35Li2O-35Nb2O5-30SiO2 glass. Laser scanning speed and power density were systematically varied to control the crystal growth process and determine the optimal conditions for the formation of single crystal lines. EBSD measurements showed that, in principle, single crystals can be grown to unlimited lengths using optimal parameters. We successfully tuned the parameters to a growth mode where nucleation and growth occur upon heating and ahead of the scanning laser focus. This growth mode eliminates the problem reported in previous works of non-uniform polycrystallinity because of a separate growth mode where crystallization occurs during cooling behind the scanning laser focus. To our knowledge, this is the first report of such a growth mode using a fs laser. The crystal cross-sections possessed a symmetric, smooth lattice misorientation with respect to the c-axis orientation in the center of the crystal. Calculations indicate the observed misorientation leads to a decrease in the refractive index of the crystal line from the center moving outwards, opening the possibility to produce within glass a graded refractive index single crystal (GRISC) optically active waveguide.

  3. Rotating lattice single crystal architecture on the surface of glass

    PubMed Central

    Savytskii, D.; Jain, H.; Tamura, N.; Dierolf, V.

    2016-01-01

    Defying the requirements of translational periodicity in 3D, rotation of the lattice orientation within an otherwise single crystal provides a new form of solid. Such rotating lattice single (RLS) crystals are found, but only as spherulitic grains too small for systematic characterization or practical application. Here we report a novel approach to fabricate RLS crystal lines and 2D layers of unlimited dimensions via a recently discovered solid-to-solid conversion process using a laser to heat a glass to its crystallization temperature but keeping it below the melting temperature. The proof-of-concept including key characteristics of RLS crystals is demonstrated using the example of Sb2S3 crystals within the Sb-S-I model glass system for which the rotation rate depends on the direction of laser scanning relative to the orientation of initially formed seed. Lattice rotation in this new mode of crystal growth occurs upon crystallization through a well-organized dislocation/disclination structure introduced at the glass/crystal interface. Implications of RLS growth on biomineralization and spherulitic crystal growth are noted. PMID:27808168

  4. Rotating lattice single crystal architecture on the surface of glass

    NASA Astrophysics Data System (ADS)

    Savytskii, D.; Jain, H.; Tamura, N.; Dierolf, V.

    2016-11-01

    Defying the requirements of translational periodicity in 3D, rotation of the lattice orientation within an otherwise single crystal provides a new form of solid. Such rotating lattice single (RLS) crystals are found, but only as spherulitic grains too small for systematic characterization or practical application. Here we report a novel approach to fabricate RLS crystal lines and 2D layers of unlimited dimensions via a recently discovered solid-to-solid conversion process using a laser to heat a glass to its crystallization temperature but keeping it below the melting temperature. The proof-of-concept including key characteristics of RLS crystals is demonstrated using the example of Sb2S3 crystals within the Sb-S-I model glass system for which the rotation rate depends on the direction of laser scanning relative to the orientation of initially formed seed. Lattice rotation in this new mode of crystal growth occurs upon crystallization through a well-organized dislocation/disclination structure introduced at the glass/crystal interface. Implications of RLS growth on biomineralization and spherulitic crystal growth are noted.

  5. Some Properties Of Synthetic Single Crystal And Thin Film Diamonds

    NASA Astrophysics Data System (ADS)

    Yazu, Shuji; Sato, Shuichi; Fujimori, Naoji

    1989-01-01

    Large synthetic diamond single crystals, in sizes up to 1.4 ct, are produced on 4 commercial basis for some industrial application fields by Sumitomo Electric. The crystals are yellow colored type Ib stones which contain lower amounts of nitrogen (up to about 100 ppm) dispersed through the crystal structure in the form of singly substituting atoms. The impurity controlled type lb crystals have the highest thermal conductivity which is equivalent to that of pure type IIa crystals. Optical and thermal properties of diamond crystals are strongly affected by dispersed impurities. We studied the kinds of dispersed impurities and amounts of those impurity atoms in our synthesized crystals by SIMS. A relation of the thermal conductivities and the nitrogen concentrations of the crystals was examined. The state of nitrogen impurity in the crystals could be transformed by electron irradiation and subsequent high temperature annealing. The reaction rates for the transformation Ib nitrogen to type IaA aggregates and differences in crystal growth sectors have been studied. Vapor phase deposited diamond films are hopeful candidates for optical application of diamond. Preliminary spectroscopic analysis has been done for the free standing polycrystalline films.

  6. Measurement of single crystal surface parameters

    NASA Technical Reports Server (NTRS)

    Swanson, L. W.; Bell, A. E.; Strayer, R. W.

    1972-01-01

    The sticking coefficient and thermal desorption spectra of Cs from the (110) plane of W was investigated. A sticking coefficient of unity for the monolayer region was measured for T 250 K. Several distinct binding states were observed in the thermal desorption spectrum. Work function and electron reflection measurements were made on the (110) and (100) crystal faces of Mo. Both LEED and Auger were used to determine the orientation and cleanliness of the crystal surfaces. The work function values obtained for the (110) and (100) planes of Mo were 4.92 and 4.18 eV respectively.

  7. Growth of single crystals by vapor transport

    NASA Technical Reports Server (NTRS)

    Wiedemeier, H.

    1978-01-01

    The primary objectives of the program were to establish basic vapor transport and crystal growth properties and to determine thermodynamic, kinetic and structural parameters relevant to chemical vapor transport systems for different classes of materials. An important aspect of these studies was the observation of the effects of gravity-caused convection on the mass transport rate and crystal morphology. These objectives were accomplished through extensive vapor transport, thermochemical and structural studies on selected Mn-chalcogenides, II-VI and IV-VI compounds.

  8. Processing tungsten single crystal by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Xiao, Zhigang; Zee, Ralph H.; Begg, Lester L.

    2000-01-01

    A tungsten single crystal layer has been fabricated on molybdenum single crystal substrate through the hydrogen (H2) reduction of the tungsten hexafluoride (WF6) in low pressure. Substrate temperature, reaction chamber pressure, and flow rate of WF6 and H2, are critical process parameters during deposition. A comprehensive analysis for the effects of these parameters on single crystal layer growth has been processed and optimized growth conditions have been achieved. The different orientation of the substrate shows the different deposition rate for tungsten. Low index plane has higher deposition rate than high index plane. The kinetics of the deposition process has also been investigated. SEM surface analysis indicates that the single crystal layer is smooth in macro-scale and rough and step-growth format in micro-scale. .

  9. High-temperature alloys: Single-crystal performance boost

    NASA Astrophysics Data System (ADS)

    Schütze, Michael

    2016-08-01

    Titanium aluminide alloys are lightweight and have attractive properties for high-temperature applications. A new growth method that enables single-crystal production now boosts their mechanical performance.

  10. Large single domain 123 material produced by seeding with single crystal rare earth barium copper oxide single crystals

    DOEpatents

    Todt, V.; Miller, D.J.; Shi, D.; Sengupta, S.

    1998-07-07

    A method of fabricating bulk YBa{sub 2}Cu{sub 3}O{sub x} where compressed powder oxides and/or carbonates of Y and Ba and Cu present in mole ratios to form YBa{sub 2}Cu{sub 3}O{sub x} are heated in the presence of a Nd{sub 1+x}Ba{sub 2{minus}x}Cu{sub 3}O{sub y} seed crystal to a temperature sufficient to form a liquid phase in the YBa{sub 2}Cu{sub 3}O{sub x} while maintaining the seed crystal solid. The materials are slowly cooled to provide a YBa{sub 2}Cu{sub 3}O{sub x} material having a predetermined number of domains between 1 and 5. Crack-free single domain materials can be formed using either plate shaped seed crystals or cube shaped seed crystals with a pedestal of preferential orientation material. 7 figs.

  11. Process for Forming a High Temperature Single Crystal Canted Spring

    NASA Technical Reports Server (NTRS)

    DeMange, Jeffrey J (Inventor); Ritzert, Frank J (Inventor); Nathal, Michael V (Inventor); Dunlap, Patrick H (Inventor); Steinetz, Bruce M (Inventor)

    2017-01-01

    A process for forming a high temperature single crystal canted spring is provided. In one embodiment, the process includes fabricating configurations of a rapid prototype spring to fabricate a sacrificial mold pattern to create a ceramic mold and casting a canted coiled spring to form at least one canted coil spring configuration based on the ceramic mold. The high temperature single crystal canted spring is formed from a nickel-based alloy containing rhenium using the at least one coil spring configuration.

  12. Synthesis and Single-Crystal Growth of Ca

    SciTech Connect

    Nakatsuji, Satoru; Maeno, Yoshiteru

    2001-01-01

    For the study of the quasi-two-dimensional Mott transition system Ca{sub 2-x}Sr{sub x}RuO{sub 4}, we have succeeded in synthesizing polycrystalline samples and also growing single crystals by a floating-zone method. Details of the preparations for the entire solution range are described. The structural, transport, and magnetic properties of both polycrystalline and single-crystal samples are fully in agreement.

  13. Inhomogeneities in single crystals of cuprate oxide superconductors

    NASA Technical Reports Server (NTRS)

    Moorjani, K.; Bohandy, J.; Kim, B. F.; Adrian, F. J.

    1991-01-01

    The next stage in the evolution of experimental research on the high temperature superconductors will require high quality single crystals and epitaxially grown crystalline films. However, inhomogeneities and other defects are not uncommon in single crystals of cuprate oxide superconductors, so a corollary requirement will be a reliable method for judging the quality of these materials. The application of magnetically modulated resistance methods in this task is briefly described and illustrated.

  14. Thermal and dielectric studies of nickel malonate dihydrate single crystals

    NASA Astrophysics Data System (ADS)

    Mathew, Varghese; Mathai, K. C.; Mahadeven, C. K.; Abraham, K. E.

    2011-02-01

    Single crystals of nickel malonate dihydrate were grown by the gel technique, employing the single diffusion method. Thermal dehydration of the crystal was investigated by thermogravimetric and differential thermal analyses. The title compound exhibits a steady thermal behaviour at higher temperature range of 350-800 °C. The dielectric properties of the prepared sample were analyzed as a function of frequency in the range of 1 kHz-1 MHz and at temperatures between 40 and 140 °C.

  15. Fatigue damage modeling for coated single crystal superalloys

    NASA Technical Reports Server (NTRS)

    Nissley, David M.

    1988-01-01

    A high temperature, low-cycle fatigue life prediction method for coated single crystal nickel-base superalloys is being developed. The method is being developed for use in predicting crack initiation life of coated single crystal turbine airfoils. Although the models are being developed using coated single crystal PWA 1480, they should be readily adaptable to other coated nickel-base single crystal materials. The coatings choosen for this effort were of two generic types: a low pressure plasma sprayed NiCoCrAlY overlay, designated PWA 286, and an aluminide diffusion, designated PWA 273. In order to predict the useful crack initiation life of airfoils, the constitutive and failure behavior of the coating/substrate combination must be taken into account. Coatings alter the airfoil surface microstructure and are a primary source from which cracks originate. The adopted life prediction approach addresses this complexity by separating the coating and single crystal crack initiation regimes. This provides a flexible means for using different life model formulations for the coating and single crystal materials. At the completion of this program, all constitutive and life model formulations will be available in equation form and as software. The software will use the MARC general purpose finite element code to drive the constitutive models and calculate life parameters.

  16. Blocks and residual stresses in shaped sapphire single crystals

    NASA Astrophysics Data System (ADS)

    Krymov, V. M.; Nosov, Yu. G.; Bakholdin, S. I.; Maslov, V. N.; Shul‧pina, I. L.; Nikolaev, V. I.

    2017-01-01

    The formation of blocks and residual stresses in shaped sapphire crystals grown from the melt by the Stepanov method (EFG) has been studied. The probability of block formation is higher for the growth along the c axis compared to that grown in the a-axis direction. The distribution of residual stress in sapphire crystals of tubular, rectangular and round cross section was measured by the conoscopy method. It was found that the magnitude of the residual stress increases from the center to the periphery of the crystal and reaches up to about 20 MPa. Residual stress tensor components for solid round rod and tubular single crystals were determined by numerical integration.

  17. Growth and properties of benzil doped benzimidazole (BMZ) single crystals

    SciTech Connect

    Babu, R. Ramesh; Sukumar, M.; Vasudevan, V.; Shakir, Mohd.; Ramamurthi, K.; Bhagavannarayana, G.

    2010-09-15

    In the present work, we have made an attempt to study the effect of benzil doping on the properties of benzimidazole single crystals. For this purpose we have grown pure and benzil doped benzimidazole single crystals by vertical Bridgman technique. The grown crystals were characterized by various characterization techniques. The presence of dopants confirmed by powder X-ray diffraction (XRD). Crystalline perfection of the grown crystals has been analysed by high-resolution X-ray diffraction (HRXRD). The transmittance, electrical property and mechanical strength have been analysed using UV-vis-NIR spectroscopic, dielectric and Vicker's hardness studies. The relative second harmonic generation efficiency of pure and doped benzimidazole crystals measured using Kurtz powder test.

  18. The optical properties of alkali nitrate single crystals

    NASA Astrophysics Data System (ADS)

    Anan'ev, Vladimir; Miklin, Mikhail

    2000-08-01

    Absorption of non-polarized light by a uniaxial crystal has been studied. The degree of absorption polarization has been calculated as a function of the ratio of optical densities in the region of low and high absorbances. This function is proposed for analysis of the qualitative and quantitative characteristics of uniaxial crystal absorption spectra. Non-polarized light spectra of alkali nitrate single crystals, both pure and doped with thallium, have been studied. It is shown that the absorption band at 300 nm is due to two transitions, whose intensities depend on temperature in various ways. There is a weak band in a short wavelength range of the absorption spectrum of potassium nitrate crystal, whose intensity increases with thallium doping. The band parameters of alkali nitrate single crystals have been calculated. Low-energy transitions in the nitrate ion have been located.

  19. Fatigue Failure Criteria for Single Crystal Nickel Superalloys

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.

    1999-01-01

    High Cycle Fatigue (HCF) induced failures in aircraft gas-turbine and rocket engine turbopump blades is a pervasive problem. Single crystal turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry and NASA because of their superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys. Single-crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the pan geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades is complicated to predict due to the material orthotropy and variations in crystal orientations. A fatigue failure criteria based on the maximum shear stress amplitude [delta t max] on the 30 slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criteria reduces the scatter in uniaxial LCF test data, for four different specimen orientations, for PWA 1484 at 1200 F in air, quite well. A power law curve fit of the failure parameter, delta t max, vs. cycles to failure is presented.

  20. Anisotropy of nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Maier, R. D.; Dreshfield, R. L.

    1980-01-01

    The effects of crystal orientation on the mechanical properties of single crystals of the nickel-based superalloy Mar-M247 are investigated. Tensile tests at temperatures from 23 to 1093 C and stress rupture tests at temperatures from 760 to 1038 C were performed for 52 single crystals at various orientations. During tensile testing between 23 and 760 C, single crystals with high Schmid factors were found to be favorably oriented for slip and to exhibit lower strength and higher ductility than those with low Schmid factors. Crystals which required large rotations to become oriented for cross slip were observed to have the shortest stress rupture lives at 760 C, while those which required little or no rotation had the longest lives. In addition, stereographic triangles obtained for Mar-M247 and Mar-M200 single crystals reveal that crystals with orientations near the -111 had the highest lives, those near the 001 had high lives, and those near the 011 had low lives.

  1. An analytical model for porous single crystals with ellipsoidal voids

    NASA Astrophysics Data System (ADS)

    Mbiakop, A.; Constantinescu, A.; Danas, K.

    2015-11-01

    A rate-(in)dependent constitutive model for porous single crystals with arbitrary crystal anisotropy (e.g., FCC, BCC, HCP, etc.) containing general ellipsoidal voids is developed. The proposed model, denoted as modified variational model (MVAR), is based on the nonlinear variational homogenization method, which makes use of a linear comparison porous material to estimate the response of the nonlinear porous single crystal. Periodic multi-void finite element simulations are used in order to validate the MVAR for a large number of parameters including cubic (FCC, BCC) and hexagonal (HCP) crystal anisotropy, various creep exponents (i.e., nonlinearity), several stress triaxiality ratios, general void shapes and orientations and various porosity levels. The MVAR model, which involves a priori no calibration parameters, is found to be in good agreement with the finite element results for all cases considered in the rate-dependent context. The model is then used in a predictive manner to investigate the complex response of porous single crystals in several cases with strong coupling between the anisotropy of the crystal and the (morphological) anisotropy induced by the shape and orientation of the voids. Finally, a simple way of calibrating the MVAR with just two adjustable parameters is depicted in the rate-independent context so that an excellent agreement with the FE simulation results is obtained. In this last case, this proposed model can be thought as a generalization of the Gurson model in the context of porous single crystals and general ellipsoidal void shapes and orientations.

  2. Cladded single crystal fibers for high power fiber lasers

    NASA Astrophysics Data System (ADS)

    Kim, W.; Shaw, B.; Bayya, S.; Askins, C.; Peele, J.; Rhonehouse, D.; Meyers, J.; Thapa, R.; Gibson, D.; Sanghera, J.

    2016-09-01

    We report on the recent progress in the development of cladded single crystal fibers for high power single frequency lasers. Various rare earth doped single crystal YAG fibers with diameters down to 17 μm with length > 1 m have been successfully drawn using a state-of-the-art Laser Heated Pedestal Growth system. Single and double cladding on rare earth doped YAG fibers have been developed using glasses where optical and physical properties were precisely matched to doped YAG core single crystal fiber. The double clad Yb:YAG fiber structures have dimensions analogous to large mode area (LMA) silica fiber. We also report successful fabrications of all crystalline core/clad fibers where thermal and optical properties are superior over glass cladded YAG fibers. Various fabrication methods, optical characterization and gain measurements on these cladded YAG fibers are reported.

  3. Shock Driven Twinning in Tantalum Single Crystals

    SciTech Connect

    McNaney, J M; HSUING, L M; Barton, N R; Kumar, M

    2009-07-20

    Recovery based observations of high pressure material behavior generated under high explosively driven flyer based loading conditions are reported. Two shock pressures, 25, and 55 GPa and four orientations {l_brace}(100), (110), (111), (123){r_brace} were considered. Recovered material was characterized using electron backscatter diffraction along with a limited amount of transmission electron microscopy to assess the occurrence of twinning under each test condition. Material recovered from 25 GPa had a very small fraction of twinning for the (100), (110), and (111) oriented crystals while a more noticeable fraction of the (123) oriented crystal was twinned. Material recovered from 55 GPa showed little twinning for (100) orientation slightly more for the (111) orientation and a large area fraction for the (123) orientation. The EBSD and TEM observations of the underlying deformation substructure are rationalized by comparing with previous static and dynamic results.

  4. Magnetically induced ferroelectricity in single crystalline ferrimagnet, Mn2Mo3O8

    NASA Astrophysics Data System (ADS)

    Chikara, Shalinee; Singleton, John; Gao, Bin; Wang, Yazhong; Cheong, Sang-Wook; Zapf, Vivien

    We present magnetization and electric polarization results on multiferroic ferrimagnet molybdate system, Mn2Mo3O8 in pulsed magnetic fields. Mn2Mo3O8, also known as the mineral isiemite crystallizes in a hexagonal P63 mc space group. The magnetism is attributed to the Mn ions whereas the Mo is diamagnetic. The Mo and Mn atoms are stacked alternately along c-axis. The Mn ions form a hexagonal lattice and occur in octahedral and tetragonal coordination. The spins on two different Mn sites give rise to ferrimagnetism. The system orders at about 42 K accompanied by a lambda like anomaly in heat capacity. Mn2Mo3O8 shows anisotropic magnetization with a change in slope at 40 K signaling possibly an AFM to ferrimagnet ordering. We observe magnetic field induced electric polarization in our preliminary results and an anomaly at 40 K corresponding to TN. A portion of this work was performed at the NHMFL, which is supported by National Science Foundation Cooperative Agreement No. DMR-1157490, the State of Florida, and the U.S. Department of Energy.

  5. Quantum properties of charged ferroelectric domain walls

    NASA Astrophysics Data System (ADS)

    Sturman, B.; Podivilov, E.; Stepanov, M.; Tagantsev, A.; Setter, N.

    2015-12-01

    We consider the properties of charged domain walls in ferroelectrics as a quantum problem. This includes determination of self-consistent attracting 1D potential for compensating charge carriers, the number and positions of discrete energy levels in this potential, dependencies on the ferroelectric characteristics, as well as the spatial structure and formation energy of the wall. Our description is based on the Hartree and Thomas-Fermi methods and Landau theory for the ferroelectric transitions. Changeover from a few to many quantum levels (with the electron binding energies ˜1 eV) is controlled by a single characteristic parameter. The quantum models well describe the core of the wall, whose width is typically ˜10 nm. Additionally, the walls possess pronounced long-range tails which are due to trap recharging. For the trap concentration Nt=(1017-1018) cm-3 , the tail length ℓ is of the μ m scale. On the distances much larger than ℓ the walls are electrically uncoupled from each other and the crystal faces.

  6. Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys

    NASA Technical Reports Server (NTRS)

    Arakere, N. K.; Swanson, G.

    2002-01-01

    High cycle fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Single crystal nickel turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493, PWA 1484, RENE' N-5 and CMSX-4. These alloys play an important role in commercial, military and space propulsion systems. Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades are complicated to predict due to the material orthotropy and variations in crystal orientations. Fatigue life estimation of single crystal turbine blades represents an important aspect of durability assessment. It is therefore of practical interest to develop effective fatigue failure criteria for single crystal nickel alloys and to investigate the effects of variation of primary and secondary crystal orientation on fatigue life. A fatigue failure criterion based on the maximum shear stress amplitude /Delta(sub tau)(sub max))] on the 24 octahedral and 6 cube slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criterion reduces the scatter in uniaxial LCF test data considerably for PWA 1493 at 1200 F in air. Additionally, single crystal turbine blades used in the alternate advanced high-pressure fuel turbopump (AHPFTP/AT) are modeled using a large-scale three-dimensional finite element model. This finite element model is capable of accounting for material orthotrophy and variation in primary and secondary crystal orientation. Effects of variation in crystal orientation on blade stress response are studied based on 297

  7. Nanocharacterization of the negative stiffness of ferroelectric materials

    NASA Astrophysics Data System (ADS)

    Alipour Skandani, A.; Ctvrtlik, R.; Al-Haik, M.

    2014-08-01

    Phase changing materials such as ferroelectric materials could exhibit negative stiffness under certain thermomechanical environments. This negative stiffness is embodied by a deflection along the opposite direction of the applied load. So far negative stiffness materials were investigated with the specific morphology of embedded inclusions in stiff matrices then the resulting composite is studied to measure the behavior of each constituent indirectly. In this study, a modified nonisothermal nanoindentation method is developed to measure the negative stiffness of triglycine sulfate single crystal directly. This in-situ method is intended to first demonstrate the feasibility of detecting the negative stiffness via nanoindentation and nanocreep of a ferroelectric material at its Curie point and then to quantify the negative stiffness without the need for embedding the crystal within a stiffer matrix.

  8. Near-field resonance shifts of ferroelectric barium titanate domains upon low-temperature phase transition

    SciTech Connect

    Döring, Jonathan; Ribbeck, Hans-Georg von; Kehr, Susanne C.; Eng, Lukas M.; Fehrenbacher, Markus

    2014-08-04

    Scattering scanning near-field optical microscopy (s-SNOM) has been established as an excellent tool to probe domains in ferroelectric crystals at room temperature. Here, we apply the s-SNOM possibilities to quantify low-temperature phase transitions in barium titanate single crystals by both temperature-dependent resonance spectroscopy and domain distribution imaging. The orthorhombic-to-tetragonal structural phase transition at 263 K manifests in a change of the spatial arrangement of ferroelectric domains as probed with a tunable free-electron laser. More intriguingly, the domain distribution unravels non-favored domain configurations upon sample recovery to room temperature as explainable by increased sample disorder. Ferroelectric domains and topographic influences are clearly deconvolved even at low temperatures, since complementing our s-SNOM nano-spectroscopy with piezoresponse force microscopy and topographic imaging using one and the same atomic force microscope and tip.

  9. The demonstration of significant ferroelectricity in epitaxial Y-doped HfO2 film.

    PubMed

    Shimizu, Takao; Katayama, Kiliha; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J; Sakata, Osami; Funakubo, Hiroshi

    2016-09-09

    Ferroelectricity and Curie temperature are demonstrated for epitaxial Y-doped HfO2 film grown on (110) yttrium oxide-stabilized zirconium oxide (YSZ) single crystal using Sn-doped In2O3 (ITO) as bottom electrodes. The XRD measurements for epitaxial film enabled us to investigate its detailed crystal structure including orientations of the film. The ferroelectricity was confirmed by electric displacement filed - electric filed hysteresis measurement, which revealed saturated polarization of 16 μC/cm(2). Estimated spontaneous polarization based on the obtained saturation polarization and the crystal structure analysis was 45 μC/cm(2). This value is the first experimental estimations of the spontaneous polarization and is in good agreement with the theoretical value from first principle calculation. Curie temperature was also estimated to be about 450 °C. This study strongly suggests that the HfO2-based materials are promising for various ferroelectric applications because of their comparable ferroelectric properties including polarization and Curie temperature to conventional ferroelectric materials together with the reported excellent scalability in thickness and compatibility with practical manufacturing processes.

  10. The demonstration of significant ferroelectricity in epitaxial Y-doped HfO2 film

    NASA Astrophysics Data System (ADS)

    Shimizu, Takao; Katayama, Kiliha; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Sakata, Osami; Funakubo, Hiroshi

    2016-09-01

    Ferroelectricity and Curie temperature are demonstrated for epitaxial Y-doped HfO2 film grown on (110) yttrium oxide-stabilized zirconium oxide (YSZ) single crystal using Sn-doped In2O3 (ITO) as bottom electrodes. The XRD measurements for epitaxial film enabled us to investigate its detailed crystal structure including orientations of the film. The ferroelectricity was confirmed by electric displacement filed – electric filed hysteresis measurement, which revealed saturated polarization of 16 μC/cm2. Estimated spontaneous polarization based on the obtained saturation polarization and the crystal structure analysis was 45 μC/cm2. This value is the first experimental estimations of the spontaneous polarization and is in good agreement with the theoretical value from first principle calculation. Curie temperature was also estimated to be about 450 °C. This study strongly suggests that the HfO2-based materials are promising for various ferroelectric applications because of their comparable ferroelectric properties including polarization and Curie temperature to conventional ferroelectric materials together with the reported excellent scalability in thickness and compatibility with practical manufacturing processes.

  11. The demonstration of significant ferroelectricity in epitaxial Y-doped HfO2 film

    PubMed Central

    Shimizu, Takao; Katayama, Kiliha; Kiguchi, Takanori; Akama, Akihiro; Konno, Toyohiko J.; Sakata, Osami; Funakubo, Hiroshi

    2016-01-01

    Ferroelectricity and Curie temperature are demonstrated for epitaxial Y-doped HfO2 film grown on (110) yttrium oxide-stabilized zirconium oxide (YSZ) single crystal using Sn-doped In2O3 (ITO) as bottom electrodes. The XRD measurements for epitaxial film enabled us to investigate its detailed crystal structure including orientations of the film. The ferroelectricity was confirmed by electric displacement filed – electric filed hysteresis measurement, which revealed saturated polarization of 16 μC/cm2. Estimated spontaneous polarization based on the obtained saturation polarization and the crystal structure analysis was 45 μC/cm2. This value is the first experimental estimations of the spontaneous polarization and is in good agreement with the theoretical value from first principle calculation. Curie temperature was also estimated to be about 450 °C. This study strongly suggests that the HfO2-based materials are promising for various ferroelectric applications because of their comparable ferroelectric properties including polarization and Curie temperature to conventional ferroelectric materials together with the reported excellent scalability in thickness and compatibility with practical manufacturing processes. PMID:27608815

  12. Swimming photochromic azobenzene single crystals in triacrylate solution.

    PubMed

    Milam, Kenneth; O'Malley, Garrett; Kim, Namil; Golovaty, Dmitry; Kyu, Thein

    2010-06-17

    Self-motion of a growing single crystal of azobenzene chromophore in triacrylate solution (TA) is investigated in relation to the solid-liquid phase diagram bound by the solidus and liquidus lines. Upon thermal quenching from the isotropic melt to the crystal + liquid gap, various single crystals develop in a manner dependent on concentration and supercooling depth. During the crystal growth, TA solvent is rejected from the growing faceted fronts, enriching with TA in close proximity to the crystal-solution interface. The concentration gradient that formed as the result of TA expulsion induces convective flows in the solution and generates spatial variability of surface tension usually responsible for Marangoni effect. Either or both of these phenomena may have contributed to the observed self-motion including swimming, sinking, and floating of the azobenzene rhomboidal crystal in TA solution. A stationary rhomboidal crystal is also shown to swim upon irradiation with the UV light because of a mechanical torque generated by the trans-cis isomerization. Judging from the sinking or floating behavior of the azobenzene crystal, it may be inferred that the nucleation occurs at the solution-air interface.

  13. Method of making macrocrystalline or single crystal semiconductor material

    NASA Technical Reports Server (NTRS)

    Shlichta, P. J. (Inventor); Holliday, R. J. (Inventor)

    1986-01-01

    A macrocrystalline or single crystal semiconductive material is formed from a primary substrate including a single crystal or several very large crystals of a relatively low melting material. This primary substrate is deposited on a base such as steel or ceramic, and it may be formed from such metals as zinc, cadmium, germanium, aluminum, tin, lead, copper, brass, magnesium silicide, or magnesium stannide. These materials generally have a melting point below about 1000 C and form on the base crystals the size of fingernails or greater. The primary substrate has an epitaxial relationship with a subsequently applied layer of material, and because of this epitaxial relationship, the material deposited on the primary substrate will have essentially the same crystal size as the crystals in the primary substrate. If required, successive layers are formed, each of a material which has an epitaxial relationship with the previously deposited layer, until a layer is formed which has an epitaxial relationship with the semiconductive material. This layer is referred to as the epitaxial substrate, and its crystals serve as sites for the growth of large crystals of semiconductive material. The primary substrate is passivated to remove or otherwise convert it into a stable or nonreactive state prior to deposition of the seconductive material.

  14. REFINEMENT OF THE CRYSTAL STRUCTURE OF GUANIDINIUM ALUMINUM SULFATE HEXAHYDRATE.

    DTIC Science & Technology

    FERROELECTRIC CRYSTALS, * CRYSTAL STRUCTURE ), (*GUANIDINES, CRYSTAL STRUCTURE ), (*ALUMINUM COMPOUNDS, CRYSTAL STRUCTURE ), SULFATES, HYDRATES, X RAY DIFFRACTION, CHROMIUM COMPOUNDS, CRYSTAL LATTICES, CHEMICAL BONDS

  15. Effect of manganese doping on PIN-PMN-PT single crystals for high power applications

    NASA Astrophysics Data System (ADS)

    Sahul, Raffi

    property measurements (elastic, dielectric, and piezoelectric) for the "2R" Mn:PIN-PMN-PT single crystal poled into orthorhombic mm2 macroscopic symmetry ([011]c poled crystals) and for "4R" configuration ([001]c poled crystals) were conducted and the data was analyzed based on their macroscopic crystallographic symmetry. Full property data was measured for the 1R configuration of the Mn:PIN-PMN-PT single crystal to understand the monodomain properties and the orientation dependence of dielectric, elastic, and piezoelectric properties. Domain averaging and matrix transformation was performed with the monodomain data to calculate 4R data and compare with that of experimental 4R data. Orientation dependence of the properties is also presented to understand the crystallographic directions that are best suited for the various applications. The high sensitivity of PMN-PT and the high Qm of Mn:PIN-PMN-PT provide designers with soft and hard piezoelectric material choices in the relaxor-PT single crystals family. While much work has been done on PMN-PT crystals, research efforts on the Mn:PIN-PMN-PT crystals are limited. Investigation of the Qm for Mn-doped crystals under high power drive conditions is essential for the practical application of these crystals for devices. High power characteristics of the Mn:PIN-PMN-PT single crystals were measured with emphasis on specific modes (transverse mode, d32, and face shear mode, d36') based on a constant vibration velocity method using a high power characterization system (HiPoCs), and the degradation of Qm as a function of vibration velocity was studied in order to understand the self heating behavior and device limitations. Practical devices that are useful for various applications were designed and performance of these prototype devices was quantitatively evaluated. This thesis work provides a concrete advancement in the understanding of doped ternary relaxor-PT ferroelectric single crystals and the influence of their domain

  16. Inspection of Single Crystal Aerospace Components with Ultrasonic Arrays

    NASA Astrophysics Data System (ADS)

    Lane, C. J. L.; Dunhill, A.; Drinkwater, B. W.; Wilcox, P. D.

    2010-02-01

    Single crystal metal alloys are used extensively in the manufacture of jet engine components for their excellent mechanical properties at elevated temperatures. The increasing use of these materials and demand for longer operational life and improved reliability motivates the requirement to have capable NDE methods available. Ultrasonic arrays are well established at detecting sub-surface defects however these methods are not currently suitable to the inspection of single crystal components due to their high elastic anisotropy causing directional variation in ultrasonic waves. In this paper a model of wave propagation in anisotropic material is used to correct an ultrasonic imaging algorithm and is applied to single crystal test specimens. The orientation of the crystal in a specimen must be known for this corrected-algorithm; therefore a crystal orientation method is also presented that utilizes surface skimming longitudinal waves under a 2D array. The work detailed in this paper allows an ultrasonic 2D array to measure the orientation of a single crystal material and then perform accurate volumetric imaging to detect and size defects.

  17. Low-cost single-crystal turbine blades, volume 2

    NASA Technical Reports Server (NTRS)

    Strangman, T. E.; Dennis, R. E.; Heath, B. R.

    1984-01-01

    The overall objectives of Project 3 were to develop the exothermic casting process to produce uncooled single-crystal (SC) HP turbine blades in MAR-M 247 and higher strength derivative alloys and to validate the materials process and components through extensive mechanical property testing, rig testing, and 200 hours of endurance engine testing. These Program objectives were achieved. The exothermic casting process was successfully developed into a low-cost nonproperietary method for producing single-crystal castings. Single-crystal MAR-M 247 and two derivatives DS alloys developed during this project, NASAIR 100 and SC Alloy 3, were fully characterized through mechanical property testing. SC MAR-M 247 shows no significant improvement in strength over directionally solidified (DS) MAR-M 247, but the derivative alloys, NASAIR 100 and Alloy 3, show significant tensile and fatigue improvements. Firtree testing, holography, and strain-gauge rig testing were used to determine the effects of the anisotropic characteristics of single-crystal materials. No undesirable characteristics were found. In general, the single-crystal material behaved similarly to DS MAR-M 247. Two complete engine sets of SC HP turbine blades were cast using the exothermic casting process and fully machined. These blades were successfully engine-tested.

  18. Enhancing the Mechanical Properties of Single-Crystal CVD Diamond

    SciTech Connect

    Liang, Q.; Yan, C; Meng, Y; Lai, J; Krasnicki, S; Mao, H; Hemley, R

    2009-01-01

    Approaches for enhancing the strength and toughness of single-crystal diamond produced by chemical vapor deposition (CVD) at high growth rates are described. CVD processes used to grow single-crystal diamond in high density plasmas were modified to incorporate boron and nitrogen. Semi-quantitative studies of mechanical properties were carried out using Vickers indentation techniques. The introduction of boron in single-crystal CVD diamond can significantly enhance the fracture toughness of this material without sacrificing its high hardness ({approx}78 GPa). Growth conditions were varied to investigate its effect on boron incorporation and optical properties by means of photoluminescence, infrared, and ultraviolet-visible absorption spectroscopy. Boron can be readily incorporated into single-crystal diamond by the methods used, but with nitrogen addition, the incorporation of boron was hindered. The spectroscopic measurements indicate that nitrogen and boron coexist in the diamond structure, which helps explain the origin of the enhanced fracture toughness of this material. Further, low pressure/high temperature annealing can enhance the intrinsic hardness of single-crystal CVD diamond by a factor of two without appreciable loss in fracture toughness. This doping and post-growth treatment of diamond may lead to new technological applications that require enhanced mechanical properties of diamond.

  19. Growth of solid solution single crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, S. L.; Szofran, F. R.

    1987-01-01

    Based on the thermophysical properties of Hg sub 1-x Cd sub x Te alloys, the reasons are discussed for the failure of conventional Bridgman-Stockbarger growth methods to produce high quality homogeneous crystals in the presence of Earth's gravity. The deleterious effects are considered which arise from the dependence of the thermophysical properties on temperature and composition and from the large amount of heat carried by the fused silica ampules. An improved growth method, developed to optimize heat flow conditions, is described and experimental results are presented. The problems associated with growth in a gravitational environment are discussed. The anticipated advantages of growth in microgravity are given and the implications of the requirements for spaceflight experiments are summarized.

  20. Growth of solid solution single crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, S. L.; Szofran, F. R.

    1988-01-01

    Based on the thermophysical properties of Hg sub 1-x Cd sub x Te alloys, the reasons are discussed for the failure of conventional Bridgman-Stockbarger growth methods to produce high quality homogeneous crystals in the prescence of Earth's gravity. The deleterious effects are considered which arise from the dependence of the thermophysical properties on temperature and composition and from the large amount of heat carried by the fused silica ampules. An improved growth method, developed to optimize heat flow conditions, is described and experimental results are presented. The problems associated with growth in a gravitational environment are discussed. The anticipated advantages of growth in microgravity are given and the implications of the requirements for spaceflight experiments are summarized.

  1. Method for harvesting rare earth barium copper oxide single crystals

    DOEpatents

    Todt, V.R.; Sengupta, S.; Shi, D.

    1996-04-02

    A method of preparing high temperature superconductor single crystals is disclosed. The method of preparation involves preparing precursor materials of a particular composition, heating the precursor material to achieve a peritectic mixture of peritectic liquid and crystals of the high temperature superconductor, cooling the peritectic mixture to quench directly the mixture on a porous, wettable inert substrate to wick off the peritectic liquid, leaving single crystals of the high temperature superconductor on the porous substrate. Alternatively, the peritectic mixture can be cooled to a solid mass and reheated on a porous, inert substrate to melt the matrix of peritectic fluid while leaving the crystals melted, allowing the wicking away of the peritectic liquid. 2 figs.

  2. Geometric constraints on phase coexistence in vanadium dioxide single crystals

    NASA Astrophysics Data System (ADS)

    McGahan, Christina; Gamage, Sampath; Liang, Jiran; Cross, Brendan; Marvel, Robert E.; Haglund, Richard F.; Abate, Yohannes

    2017-02-01

    The appearance of stripe phases is a characteristic signature of strongly correlated quantum materials, and its origin in phase-changing materials has only recently been recognized as the result of the delicate balance between atomic and mesoscopic materials properties. A vanadium dioxide (VO2) single crystal is one such strongly correlated material with stripe phases. Infrared nano-imaging on low-aspect-ratio, single-crystal VO2 microbeams decorated with resonant plasmonic nanoantennas reveals a novel herringbone pattern of coexisting metallic and insulating domains intercepted and altered by ferroelastic domains, unlike previous reports on high-aspect-ratio VO2 crystals where the coexisting metal/insulator domains appear as alternating stripe phases perpendicular to the growth axis. The metallic domains nucleate below the crystal surface and grow towards the surface with increasing temperature as suggested by the near-field plasmonic response of the gold nanorod antennas.

  3. Single-crystal structure of a covalent organic framework.

    PubMed

    Zhang, Yue-Biao; Su, Jie; Furukawa, Hiroyasu; Yun, Yifeng; Gándara, Felipe; Duong, Adam; Zou, Xiaodong; Yaghi, Omar M

    2013-11-06

    The crystal structure of a new covalent organic framework, termed COF-320, is determined by single-crystal 3D electron diffraction using the rotation electron diffraction (RED) method for data collection. The COF crystals are prepared by an imine condensation of tetra-(4-anilyl)methane and 4,4'-biphenyldialdehyde in 1,4-dioxane at 120 °C to produce a highly porous 9-fold interwoven diamond net. COF-320 exhibits permanent porosity with a Langmuir surface area of 2400 m(2)/g and a methane total uptake of 15.0 wt % (176 cm(3)/cm(3)) at 25 °C and 80 bar. The successful determination of the structure of COF-320 directly from single-crystal samples is an important advance in the development of COF chemistry.

  4. Single-Crystal Structure of a Covalent Organic Framework

    SciTech Connect

    Zhang, YB; Su, J; Furukawa, H; Yun, YF; Gandara, F; Duong, A; Zou, XD; Yaghi, OM

    2013-11-06

    The crystal structure of a new covalent organic framework, termed COF-320, is determined by single-crystal 3D electron diffraction using the rotation electron diffraction (RED) method for data collection. The COF crystals are prepared by an imine condensation of tetra-(4-anilyl)methane and 4,4'-biphenyldialdehyde in 1,4-dioxane at 120 degrees C to produce a highly porous 9-fold interwoven diamond net. COF-320 exhibits permanent porosity with a Langmuir surface area of 2400 m(2)/g and a methane total uptake of 15.0 wt % (176 cm(3)/cm(3)) at 25 degrees C and 80 bar. The successful determination of the structure of COF-320 directly from single-crystal samples is an important advance in the development of COF chemistry.

  5. Studying the magnetic properties of CoSi single crystals

    SciTech Connect

    Narozhnyi, V. N. Krasnorussky, V. N.

    2013-05-15

    The magnetic properties of CoSi single crystals have been measured in a range of temperatures T = 5.5-450 K and magnetic field strengths H {<=} 11 kOe. A comparison of the results for crystals grown in various laboratories allowed the temperature dependence of magnetic susceptibility {chi}(T) = M(T)/H to be determined for a hypothetical 'ideal' (free of magnetic impurities and defects) CoSi crystal. The susceptibility of this ideal crystal in the entire temperature range exhibits a diamagnetic character. The {chi}(T) value significantly increases in absolute value with decreasing temperature and exhibits saturation at the lowest temperatures studied. For real CoSi crystals of four types, paramagnetic contributions to the susceptibility have been evaluated and nonlinear (with respect to the field) contributions to the magnetization have been separated and taken into account in the calculations of {chi}(T).

  6. Growth and characterization of lithium yttrium borate single crystals

    SciTech Connect

    Singh, A. K.; Singh, S. G.; Tyagi, M.; Desai, D. G.; Sen, Shashwati

    2014-04-24

    Single crystals of 0.1% Ce doped Li{sub 6}Y(BO{sub 3}){sub 3} have been grown using the Czochralski technique. The photoluminescence study of these crystals shows a broad emission at ∼ 420 nm corresponding to Ce{sub 3+} emission from 5d→4f energy levels. The decay profile of this emission shows a fast response of ∼ 28 ns which is highly desirable for detector applications.

  7. Isotropic behavior of an anisotropic material: single crystal silicon

    NASA Astrophysics Data System (ADS)

    McCarter, Douglas R.; Paquin, Roger A.

    2013-09-01

    Zero defect single crystal silicon (Single-Crystal Si), with its diamond cubic crystal structure, is completely isotropic in most properties important for advanced aerospace systems. This paper will identify behavior of the three most dominant planes of the Single-Crystal Si cube (110), (100) and (111). For example, thermal and optical properties are completely isotropic for any given plane. The elastic and mechanical properties however are direction dependent. But we show through finite element analysis that in spite of this, near-isotropic behavior can be achieved with component designs that utilize the optimum elastic modulus in directions with the highest loads. Using glass frit bonding to assemble these planes is the only bonding agent that doesn't degrade the performance of Single-Crystal Si. The most significant anisotropic property of Single-Crystal Si is the Young's modulus of elasticity. Literature values vary substantially around a value of 145 GPa. The truth is that while the maximum modulus is 185 GPa, the most useful <110< crystallographic direction has a high 169 GPa, still higher than that of many materials such as aluminum and invar. And since Poisson's ratio in this direction is an extremely low 0.064, distortion in the plane normal to the load is insignificant. While the minimum modulus is 130 GPa, a calculated average value is close to the optimum at approximately 160 GPa. The minimum modulus is therefore almost irrelevant. The (111) plane, referred to as the natural cleave plane survives impact that would overload the (110) and/or (100) plane due to its superior density. While mechanical properties vary from plane to plane each plane is uniform and response is predictable. Understanding the Single-Crystal Si diamond cube provides a design and manufacture path for building lightweight Single-Crystal Si systems with near-isotropic response to loads. It is clear then that near-isotropic elastic behavior is achievable in Single-Crystal Si

  8. Single crystals of Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-35 mol% PbTiO from polycrystalline precursors

    SciTech Connect

    Li, T.; Scotch, A.M.; Chan, H.M.; Harmer, M.P.; Park, S.E.; Shrout, T.R.; Michael, J.R.

    1998-01-01

    A potentially more cost-efficient method of growing single-crystal relaxor-based ferroelectric materials has been investigated. Seed single crystals of Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3} (PMN)-35 mol% PbTiO{sub 3} (PT) were embedded within polycrystalline powders and annealed at temperatures from 900--1,200 C. The boundary of the single crystal migrated through the polycrystal matrix under the influence of grain boundary curvature; growth distances of several millimeters were observed, verifying the feasibility of the approach. The grown single crystals exhibited macroscopic cubic growth morphologies with (100) faces. Strain levels as high as 0.68% under an electric field of 30 kV/cm were observed in initial measurements.

  9. Skylab experiments on semiconductors and alkali halides. [single crystal growth

    NASA Technical Reports Server (NTRS)

    Lundquist, C. A.

    1974-01-01

    The space processing experiments performed during the Skylab missions included one on single crystal growth of germanium selenide and telluride, one on pure and doped germanium crystals, two on pure and doped indium antimonide, one on gallium-indium-antimony systems, and one on a sodium chloride-sodium fluoride eutectic. In each experiment, three ampoules of sample were processed in the multipurpose electric furnace within the Skylab Materials Processing Facility. All were successful in varying degrees and gave important information about crystal growth removed from the effects of earth surface gravity.

  10. Single Crystal Fibers of MGO:LiNbO3

    DTIC Science & Technology

    1990-08-07

    Fibers, MgO:LiNbO39 Nonlinear Optics Crystal Growth 19 ABSTRACT (Continue on reverse if necessary and identify by block number) As optical instruments...Significant success has already been achieved at Stanford University in the growth of single crystal fibers of MgO:LiNbO3 as frequency doublers. LaserGenics...preparpd frnm singlye crystal material grown y Crstal Inc We also investigated the post growth anneai to minimize loof Prtc, ;jnon ro\\en loss in the

  11. Small- and strong-signal dielectric response in a single-crystal film of partially deuterated betaine phosphite

    NASA Astrophysics Data System (ADS)

    Balashova, E. V.; Krichevtsov, B. B.; Lemanov, V. V.

    2011-06-01

    Poly- and single-crystal films of betaine phosphite deuterated to ˜20% have been grown by evaporation on NdGaO3 (001) substrates with a preliminarily deposited planar interdigital structure of electrodes. The small-signal dielectric response in the 0.1-100.0-kHz frequency range has revealed a strong anomaly in capacitance upon the transition of the films to the ferroelectric state. Application of a bias field brings about suppression and a slight shift of the dielectric anomaly toward higher temperatures. The strong-signal dielectric response has been studied by the Sawyer-Tower method over the frequency range 0.06-3.00 kHz both in the para- and ferroelectric phases. In contrast to the case of a plane-parallel capacitor, in the planar structure studied, the dielectric hysteresis loops exhibit a very small coercivity at low frequencies, which grows with increasing frequency. This difference should be assigned to different domain structures formed in a planeparallel capacitor and in a planar structure in a saturating field. The growth of hysteresis with increasing frequency in a planar structure is considered to be associated with the domain wall motion.

  12. Low dimensional magnetic solids and single crystal elpasolites: Need for improved crystal growing techniques

    NASA Technical Reports Server (NTRS)

    Good, M. L.; Watkins, S.; Schwartz, R. W.

    1979-01-01

    The need for extensive crystal growing experiments to develop techniques for preparing crystals suitable for magnetic anisotropy measurements and detailed X-ray and neutron diffraction studies is rationalized on the basis of the unique magnetic properties of the materials and their hydrogen bonded structures which have many features in common with metalloenzyme and metalloprotein active sites. Single crystals of the single and mixed lanthanide species are prepared by the Bridgeman technique of gradient solidification of molten samples. The effects of crystal imperfections on the optical properties of these materials are an important part of the projected research. A series of a-amido acid complexes of first row transition metals were prepared which crystallize as infinite linear chains and exhibit low dimensional magnetic ordering (one or two) at temperature below 40 K.

  13. Fabrication and characterization of dielectric strontium titanium oxynitride single crystal

    NASA Astrophysics Data System (ADS)

    Hoshina, Takuya; Sahashi, Akira; Takeda, Hiroaki; Tsurumi, Takaaki

    2015-10-01

    In this paper, we show a fabrication method and the dielectric properties of strontium titanium oxynitride (SrTiO3:N) single crystals. Oxynitride single crystals were prepared by annealing SrTiO3 single crystals in gaseous ammonia. SrTiO3:N was assumed to have the chemical composition SrTiO3-3xN2x, which contained oxygen vacancies. To reduce the number of oxygen vacancies, SrTiO3 crystals co-doped with nitrogen and niobium (SrTiO3:N,Nb) were fabricated. The semiconducting Nb-doped SrTiO3 crystals changed to dielectric N,Nb-codoped SrTiO3 crystals with a resistivity of 6 × 1012 Ω·cm with annealing in gaseous ammonia. XPS measurement indicated that niobium doping was effective for increasing the amount of dopant nitrogen. The dielectric permittivity increased with the amount of dopant nitrogen, indicating the effectivity of nitrogen doping for increasing the dielectric permittivity of perovskite oxides.

  14. Single-Crystal Elasticity of Earth Materials: An Appraisal

    NASA Astrophysics Data System (ADS)

    Duffy, T. S.

    2015-12-01

    The elastic properties of minerals are of central importance for interpreting seismic data for the Earth's crust, mantle, and core. Mineral elasticity data also have more general applications towards understanding equations of state, phase equilibria, interatomic forces, material strength, and phase transitions. The singe-crystal elastic properties are the most generally useful as they provide complete information on the anisotropy of elastic moduli (e.g. Poisson's ratio, Young's modulus), sound velocities, and compressibility. Measurement of the full set of single-crystal elastic properties remains challenging especially for lower symmetry crystals. In this talk, I present an overview of our current understanding of single-crystal elasticity based on a newly constructed database of single-crystal elastic properties. At ambient conditions the full elastic tensor of about 150 minerals have now been measured, along with about another 60 related compounds that are not formally minerals. About two-thirds of the measured minerals are oxides or silicates. A limitation of the existing database is that only about 10% of the measurements are on crystals of monoclinic or triclinic symmetry, while these two systems account for about 40% of known minerals. Additionally, only a smaller subset of minerals have been examined at high pressure or temperature conditions. Several applications of the database will be presented emphasizing trends in elastic anisotropy. The pyroxenes will be used as an illustrative example.

  15. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, F. R.; Gillies, Donald C.; Watring, D. A.

    1999-01-01

    The solidification of a solid solution semiconductor, having a wide separation between liquidus and serious has been extensively studied in ground based, high magnetic field and Spacelab experiments. Two alloys of mercury cadmium telluride have been studied; mercury cadmium telluride with 80.0 mole percent of HgTe and 84.8 mole percent respectively. These alloys are extremely difficult to grow by directional solidification on earth due to high solutal and thermal density differences that give rise to fluid flow and consequent loss of interface shape and composition. Diffusion controlled growth is therefore impossible to achieve in conventional directional solidification. The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces, NASA's Advanced Automated Directional Solidification Furnace (AADSF), and a similar furnace incorporated in a superconducting magnet capable of operating at up to 5T. The first microgravity experiment took place during the flight of STS-62 in March 1994, with the AADSF installed on the second United States Microgravity Payload (USMP-2). The alloy was solidified at 3/4 inch per day over a 9 day period, and for the first time a detailed evaluation was performed of residual acceleration effects. The second flight experiment took place in the fourth United States Microgravity Payload Mission (USMP-4) in November 1997. Due to contamination of the furnace system by a previously processed sample, the sample was not received until May 1998, and the preliminary analysis shows that the conditions prevailing during the experiment were quite different from the requirements requested prior to the mission. Early results are indicating that the sample may not accomplish the desired objectives. As with the USMP-2 mission, the results of the ground based experiments were compared with the crystal grown in orbit under microgravity conditions. On the earth, it has been demonstrated that the

  16. Effect of Crystal Orientation on Analysis of Single-Crystal, Nickel-Based Turbine Blade Superalloys

    NASA Technical Reports Server (NTRS)

    Swanson, G. R.; Arakere, N. K.

    2000-01-01

    High-cycle fatigue-induced failures in turbine and turbopump blades is a pervasive problem. Single-crystal nickel turbine blades are used because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities. Single-crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant and complicating factor. A fatigue failure criterion based on the maximum shear stress amplitude on the 24 octahedral and 6 cube slip systems is presented for single-crystal nickel superalloys (FCC crystal). This criterion greatly reduces the scatter in uniaxial fatigue data for PWA 1493 at 1,200 F in air. Additionally, single-crystal turbine blades used in the Space Shuttle main engine high pressure fuel turbopump/alternate turbopump are modeled using a three-dimensional finite element (FE) model. This model accounts for material orthotrophy and crystal orientation. Fatigue life of the blade tip is computed using FE stress results and the failure criterion that was developed. Stress analysis results in the blade attachment region are also presented. Results demonstrate that control of crystallographic orientation has the potential to significantly increase a component's resistance to fatigue crack growth without adding additional weight or cost.

  17. Mechanical properties of hydroxyapatite single crystals from nanoindentation data

    PubMed Central

    Zamiri, A.; De, S.

    2011-01-01

    In this paper we compute elasto-plastic properties of hydroxyapatite single crystals from nanindentation data using a two-step algorithm. In the first step the yield stress is obtained using hardness and Young’s modulus data, followed by the computation of the flow parameters. The computational approach is first validated with data from existing literature. It is observed that hydroxyapatite single crystals exhibit anisotropic mechanical response with a lower yield stress along the [1010] crystallographic direction compared to the [0001] direction. Both work hardening rate and work hardening exponent are found to be higher for indentation along the [0001] crystallographic direction. The stress-strain curves extracted here could be used for developing constitutive models for hydroxyapatite single crystals. PMID:21262492

  18. Surface enhanced raman spectroscopy studies on triglycine sulphate single crystals

    NASA Astrophysics Data System (ADS)

    Parameswari, A.; Mohamed Asath, R.; Premkumar, R.; Milton Franklin Benial, A.

    2017-01-01

    Adsorption characteristics of triglycine sulphate (TGS) on silver (Ag) surface were investigated based on density functional theory calculations and surface enhanced Raman spectroscopy (SERS) technique. The single crystals of TGS were grown by slow evaporation method. Ag nanoparticles (Ag NPs) were prepared by solution combustion method and characterized. The calculated and observed structural parameters of TGS molecule were compared. Raman and SERS spectra for TGS single crystal were studied experimentally and validated theoretically. Frontier molecular orbitals (FMOs) analysis was carried out for TGS and TGS adsorbed on Ag surface. The second harmonic generation measurements confirm the nonlinear optical (NLO) activity of the TGS molecule. SERS spectral analysis reveals that the TGS adsorbed as tilted orientation on the silver surface. The theoretical and experimental results evidence the suitability of the grown TGS single crystal for optoelectronic applications.

  19. The Load Capability of Piezoelectric Single Crystal Actuators

    NASA Technical Reports Server (NTRS)

    Xu, Tian-Bing; Su, Ji; Jiang, Xiaoning; Rehrig, Paul W.; Hackenberger, Wesley S.

    2006-01-01

    Piezoelectric lead magnesium niobate-lead titanate (PMN-PT) single crystal is one of the most promising materials for electromechanical device applications due to its high electrical field induced strain and high electromechanical coupling factor. PMN-PT single crystal-based multilayer stack actuators and multilayer stack-based flextensional actuators have exhibited high stroke and high displacement-voltage ratios. The actuation capabilities of these two actuators were evaluated using a newly developed method based upon a laser vibrometer system under various loading conditions. The measured displacements as a function of mechanical loads at different driving voltages indicate that the displacement response of the actuators is approximately constant under broad ranges of mechanical load. The load capabilities of these PMN-PT single crystal-based actuators and the advantages of the capability for applications will be discussed.

  20. The Load Capability of Piezoelectric Single Crystal Actuators

    NASA Technical Reports Server (NTRS)

    Xu, Tian-Bing; Su, Ji; Jiang, Xiaoning; Rehrig, Paul W.; Hackenberger, Wesley S.

    2007-01-01

    Piezoelectric lead magnesium niobate-lead titanate (PMN-PT) single crystal is one of the most promising materials for electromechanical device applications due to its high electrical field induced strain and high electromechanical coupling factor. PMN-PT single crystal-based multilayer stack actuators and multilayer stack-based flextensional actuators have exhibited high stroke and high displacement-voltage ratios. The actuation capabilities of these two actuators were evaluated using a newly developed method based upon a laser vibrometer system under various loading conditions. The measured displacements as a function of mechanical loads at different driving voltages indicate that the displacement response of the actuators is approximately constant under broad ranges of mechanical load. The load capabilities of these PMN-PT single crystal-based actuators and the advantages of the capability for applications will be discussed.

  1. Single crystal optic elements for helium atom microscopy

    NASA Astrophysics Data System (ADS)

    MacLaren, D. A.; Allison, W.; Holst, B.

    2000-07-01

    Focusing characteristics of asymmetrically bent single crystal mirrors are discussed in the context of fabricating an optic element for an helium atom microscope. We demonstrate the principle that deforming a clamped, elliptical, single crystal under electrostatic pressure can produce submicron focusing of an helium beam. We present a systematic procedure that may be used to fabricate high precision mirrors close to the Cartesian ideal of any chosen optical configuration. In particular, imaging systems with asymmetric mirror profiles are discussed. Results are independent of crystal characteristics and can be adapted to fit a range of experimental geometries. The calculations indicate that mirror-induced aberrations can be eliminated to fourth order by use of a single actuation electrode in an ideal system.

  2. Mechanical properties of hydroxyapatite single crystals from nanoindentation data.

    PubMed

    Zamiri, A; De, S

    2011-02-01

    In this paper we compute elastoplastic properties of hydroxyapatite single crystals from nanoindentation data using a two-step algorithm. In the first step the yield stress is obtained using hardness and Young's modulus data, followed by the computation of the flow parameters. The computational approach is first validated with data from the existing literature. It is observed that hydroxyapatite single crystals exhibit anisotropic mechanical response with a lower yield stress along the [1010] crystallographic direction compared to the [0001] direction. Both work hardening rate and work hardening exponent are found to be higher for indentation along the [0001] crystallographic direction. The stress-strain curves extracted here could be used for developing constitutive models for hydroxyapatite single crystals.

  3. Single Crystal Synthesis and STM Studies of High Temperature Superconductors

    NASA Technical Reports Server (NTRS)

    Barrientos, Alfonso

    1997-01-01

    This is a final report for the work initiated in September of 1994 under the grant NAG8-1085 - NASA/OMU, on the fabrication of bulk and single crystal synthesis, specific heat measuring and STM studies of high temperature superconductors. Efforts were made to fabricate bulk and single crystals of mercury based superconducting material. A systematic thermal analysis on the precursors for the corresponding oxides and carbonates were carried out to synthesized bulk samples. Bulk material was used as seed in an attempt to grow single crystals by a two-step self flux process. On the other hand bulk samples were characterized by x-ray diffraction, electrical resistivity and magnetic susceptibility, We studied the specific heat behavior in the range from 80 to 300 K. Some preliminary attempts were made to study the atomic morphology of our samples. As part of our efforts we built an ac susceptibility apparatus for measuring the transition temperature of our sintered samples.

  4. Heterogeneous Monolithic Integration of Single-Crystal Organic Materials.

    PubMed

    Park, Kyung Sun; Baek, Jangmi; Park, Yoonkyung; Lee, Lynn; Hyon, Jinho; Koo Lee, Yong-Eun; Shrestha, Nabeen K; Kang, Youngjong; Sung, Myung Mo

    2017-02-01

    Manufacturing high-performance organic electronic circuits requires the effective heterogeneous integration of different nanoscale organic materials with uniform morphology and high crystallinity in a desired arrangement. In particular, the development of high-performance organic electronic and optoelectronic devices relies on high-quality single crystals that show optimal intrinsic charge-transport properties and electrical performance. Moreover, the heterogeneous integration of organic materials on a single substrate in a monolithic way is highly demanded for the production of fundamental organic electronic components as well as complex integrated circuits. Many of the various methods that have been designed to pattern multiple heterogeneous organic materials on a substrate and the heterogeneous integration of organic single crystals with their crystal growth are described here. Critical issues that have been encountered in the development of high-performance organic integrated electronics are also addressed.

  5. Local control of magnetic anisotropy in transcritical permalloy thin films using ferroelectric BaTiO3 domains

    NASA Astrophysics Data System (ADS)

    Fackler, Sean W.; Donahue, Michael J.; Gao, Tieren; Nero, Paris N. A.; Cheong, Sang-Wook; Cumings, John; Takeuchi, Ichiro

    2014-11-01

    We investigated the local coupling between dense magnetic stripe domains in transcritical permalloy (tPy) thin films and ferroelectric domains of BaTiO3 single crystals in a tPy/BaTiO3 heterostructure. Two distinct changes in the magnetic stripe domains of tPy were observed from the magnetic force microscopy images after cooling the heterostructure from above the ferroelectric Curie temperature of BaTiO3 (120 °C) to room temperature. First, an abrupt break in the magnetic stripe domain direction was found at the ferroelectric a-c-domain boundaries due to an induced change in in-plane magnetic anisotropy. Second, the magnetic stripe domain period increased when coupled to a ferroelectric a-domain due to a change in out-of-plane magnetic anisotropy. Micromagnetic simulations reveal that local magnetic anisotropy energy from inverse magnetostriction is conserved between in-plane and out-of-plane components.

  6. Anisotropy of nickel-base superalloy single crystals

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Dreshfield, R. L.; Maier, R. D.

    1980-01-01

    The influence of orientation on the tensile and stress rupture behavior of 52 Mar-M247 single crystals was studied. Tensile tests were performed at temperatures between 23 and 1093 C; stress rupture behavior was examined between 760 and 1038 C. The mechanical behavior of the single crystals was rationalized on the basis of the Schmid factor contours for the operative slip systems and the lattice rotations which the crystals underwent during deformation. The tensile properties correlated well with the appropriate Schmid factor contours. The stress rupture lives at lower testing temperatures were greatly influenced by the lattice rotations required to produce cross slip. A unified analysis was attained for the stress rupture life data generated for the Mar-M247 single crystals at 760 and 774 C under a stress of 724 MPa and the data reported for Mar-M200 single crystals tested at 760 C under a stress of 689 MPa. Based on this analysis, the stereographic triangle was divided into several regions which were rank ordered according to stress rupture life for this temperature regime.

  7. Ferroelectric domain engineering and micro-structuring of lithium niobate

    NASA Astrophysics Data System (ADS)

    Mailis, Sakellaris

    2010-11-01

    This paper discusses a number of recently developed all optical and optically assisted methods for ferroelectric domain engineering in lithium niobate and their impact on the micro-structuring of this optical ferroelectric crystal. Optical radiation is used to change the response of lithium niobate crystals to externally applied electric field encouraging or inhibiting ferroelectric domain inversion in a simultaneous or latent manner. Optically assisted poling processes have the advantage of producing ferroelectric domains with arbitrary shapes free from crystal symmetry restrictions which is very important for fabricating surface micro/nano-structures in this material.

  8. Structure and properties of Pb(Lu{sub 1/2}Nb{sub 1/2})O{sub 3}–0.2PbTiO{sub 3} relaxor ferroelectric crystal

    SciTech Connect

    Liu, Ying; Yang, Xiaoming; Lai, Fachun; Huang, Zhigao; Li, Xiuzhi; Wang, Zujian; He, Chao; Lin, Ju; Long, Xifa

    2015-07-15

    Graphical abstract: The relaxor state of the crystal was demonstrated by the dielectric behavior. - Highlights: • PLN–0.2PT ferroelectric crystal was obtained by the TSSG technique. • The super-lattice reflections were identified by XRD and TEM results. • The PLN–0.2PT crystal is a typical relaxor ferroelectric. - Abstract: Ferroelectric crystal Pb(Lu{sub 1/2}Nb{sub 1/2})O{sub 3}–0.2PbTiO{sub 3} (PLN–0.2PT) was successfully obtained by a top-seed solution growth technique. At room temperature the symmetry was orthorhomic according to X-ray diffraction (XRD). The super-lattice reflections were identified by XRD and transmission electron microscope (TEM). The micro-domain structure was detected by TEM. The temperature dependence of the dielectric constant (ϵ′) shows a typical relaxor behavior. The temperature dependence of coercive electric field and remnant polarizations were investigated, which also shows the relaxor feature.

  9. Modeling of elastic and plastic waves for HCP single crystals in a 3D formulation based on zinc single crystal

    NASA Astrophysics Data System (ADS)

    Krivosheina, Marina; Kobenko, Sergey; Tuch, Elena; Kozlova, Maria

    2016-11-01

    This paper investigates elastic and plastic waves in HCP single crystals through the numerical simulation of strain processes in anisotropic materials based on a zinc single crystal. Velocity profiles for compression waves in the back surfaces of single-crystal zinc plates with impact loading oriented in 0001 and 10 1 ¯0 are presented in this work as a part of results obtained in numerical simulations. The mathematical model implemented in this study reflects the following characteristics of the mechanical properties inherent in anisotropic (transtropic) materials: varying degree of anisotropy of elastic and plastic properties, which includes reverse anisotropy, dependence of distribution of all types of waves on the velocity orientation, and the anisotropy of compressibility. Another feature of elastic and plastic waves in HCP single crystals is that the shock wave does not split into an elastic precursor and "plastic" compression shock wave, which is inherent in zinc single crystals with loading oriented in 0001. The study compares numerical results obtained in a three-dimensional formulation with the results of velocity profiles from the back surfaces of target plates obtained in real experiments. These results demonstrate that the mathematical model is capable of describing the properties of the above-mentioned anisotropic (transtropic) materials.

  10. Crystal growth and characterization of new semiorganic nonlinear optical single crystals

    NASA Astrophysics Data System (ADS)

    Kulshrestha, Shobha; Shrivastava, A. K.

    2016-05-01

    An organic material of a L-histidine monohydrochloride single crystal was grown in a distilled water solution using the slow evaporation method at 40-45°C. The grown crystal was transparent and colourless, with a size of about 20 × 9 × 5 mm3, obtained within a period of 21 days. The solubility of grown crystals have found out at various temperatures. The UV-visible transmittance studies show that the grown crystals have wide optical transparency in the entire visible region It is observed that the crystal has transparency window from 255nm to 700nm and its energy gap (Eg) found to be is 3.1eV. The grown crystal was subjected to powder X-ray diffraction analysis, confirming that the orthorhombic crystalline nature of the crystal. To identify the surface morphology, the as grown crystal was subjected to FE-SEM technique. The chemical composition of the grown crystal was estimated by Energy dispersive X-ray analysis. The optical behaviour of the grown crystal was analyzed by PL study.

  11. Apparatus And Method For Producing Single Crystal Metallic Objects

    DOEpatents

    Huang, Shyh-Chin; Gigliotti, Jr., Michael Francis X.; Rutkowski, Stephen Francis; Petterson, Roger John; Svec, Paul Steven

    2006-03-14

    A mold is provided for enabling casting of single crystal metallic articles including a part-defining cavity, a sorter passage positioned vertically beneath and in fluid communication with the part-defining cavity, and a seed cavity positioned vertically beneath and in fluid communication with the sorter passage. The sorter passage includes a shape suitable for encouraging a single crystal structure in solidifying molten metal. Additionally, a portion of the mold between the sorter passage and the part-defining cavity includes a notch for facilitating breakage of a cast article proximate the notch during thermal stress build-up, so as to prevent mold breakage or the inclusion of part defects.

  12. Lead pyrovanadate single crystal as a new SRS material

    SciTech Connect

    Basiev, Tasoltan T; Voronko, Yu K; Maslov, Vladislav A; Sobol, A A; Shukshin, V E

    2011-02-28

    Lead pyrovanadate Pb{sub 2}V{sub 2}O{sub 7} single crystals of optical quality suitable for laser experiments are obtained. Vibrational modes are identified based on the analysis of the polarised Raman spectra of the single crystals. The main parameters (width at half maximum, peak and integral intensities) of the spectral lines most promising for SRS conversion in this material are estimated. These parameters are compared with the corresponding parameters of the most frequently used lines of known Raman materials: yttrium and gadolinium vanadates, potassium and lead tungstates, and lead molybdate. (active media)

  13. Current Noise in Sodium Beta Alumina Ceramics and Single Crystals.

    DTIC Science & Technology

    1986-08-01

    AD-Ai7O 412 CURRENT NOISE IN SODIUM BETA ALUMINA CERAMICS AIND t/l SINGLE CRYSTALS(U) UTAH UNIV SALT LAKE CITY DEPT OF PHYSICS J J BROPHY’ 81 AUG 86...ZIP C-0- UNIVERSITY OF UTAH UNIVERSITY OF NEW MEXICO SALT LAKE CITY, UTAH 84112 Bandelier Hall West Albuquerque, NM 87131 go NAME OF FUNDING...bloeS nIumbe Conductivity fluctuations and contact noise observed in ceramic and single crystal silver 811 alumina are very pilar to those in sodium 8

  14. Growth of Solid Solution Single Crystals

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, F. R.; Gillies, Donald C.

    2001-01-01

    The solidification of a solid solution semiconductor, having a wide separation between liquidus and solidus has been extensively studied in ground based, high magnetic field and Spacelab experiments. Two alloys of mercury cadmium telluride have been studied; with 80.0 mole percent of HgTe and 84.8 mole percent of HgTe respectively, the remainder being cadmium telluride. Such alloys are extremely difficult to grow by directional solidification on earth due to high solutal and thermal density differences that give rise to fluid flow and consequent loss of interface shape and composition. Diffusion controlled growth is therefore impossible to achieve in conventional directional solidification. The ground based experiments consisted of growing crystals in several different configurations of heat pipe furnaces, NASA's Advanced Automated Directional Solidification Furnace (AADSF), and a similar furnace incorporated in a superconducting magnet capable of operating at up to 5T. The first microgravity experiment took place during the flight of STS-62 in March 1994, with the AADSF installed on the second United States Microgravity Payload (USMP-2). The alloy was solidified at 3/4 inch per day over a 9 day period, and for the first time a detailed evaluation was performed correlating composition variations to measured residual acceleration. The second flight experiment took place in the fourth United States Microgravity Payload Mission (USMP-4) in November 1997. Due to contamination of the furnace system, analysis shows that the conditions prevailing during the experiment were quite different from the requirements requested prior to the mission. The results indicate that the sample did accomplish the desired objectives.

  15. Insertion of Guest Molecules into a Mixed Ligand Metal-Organic Framework via Single-Crystal-to-Single Crystal Guest Exchange

    DTIC Science & Technology

    2014-07-01

    Insertion of Guest Molecules into a Mixed Ligand Metal−Organic Framework via Single-Crystal-to-Single- Crystal Guest Exchange by Lily Giri...Research Laboratory Aberdeen Proving Ground, MD 21005-5069 ARL-TR-7004 July 2014 Insertion of Guest Molecules into a Mixed Ligand Metal−Organic...Framework via Single-Crystal-to-Single- Crystal Guest Exchange Lily Giri, Rose Pesce-Rodriguez, Shashi P Karna, and Nirupam J Trivedi Weapons

  16. Deformation of ⊥m single quartz crystals

    NASA Astrophysics Data System (ADS)

    Krasner, P.; Holyoke, C. W., III; Kronenberg, A. K.

    2015-12-01

    The rheology of quartz deformed by dislocation creep is essential to understanding the strength of the mid to lower continental crust. Our current understanding of quartz rheology is derived primarily from studies of polycrystalline quartz and little is known about the temperature, strain rate, or water dependence of the individual quartz slip systems. In order to better understand the rheology of quartz slip systems, we have deformed synthetic quartz single crystals with the prism oriented at 45° to the compression direction (⊥m orientation). We converted the gel-type water found in synthetic quartz crystals to free water fluid inclusions, similar to water observed in milky quartz crystals, by annealing the crystals at 900°C/0.1 MPa for 24 hours. The single crystals were deformed at a confining pressure of 1.5 GPa with temperatures of 850 to 1000°C and strain rates of 10-6 to 10-4/s. FTIR measurements of water concentrations in the starting material, annealed synthetic crystals and deformed synthetic quartz crystals indicate that the water concentrations (125-300 H/106Si) are not affected by the annealing process or deformation. However, the spectra in the annealed and deformed samples are similar to those of natural milky quartz rather than those of synthetic quartz. Results of temperature and strain rate stepping experiments indicate that the strength of the crystals decreases with increasing temperature and/or decreasing strain rate. Undulatory extinction is the predominant microstructure observed in deformed samples, which is consistent with deformation by dislocation creep. The strength of the ⊥m oriented quartz crystals deformed in this study with free water is greater than those of the studies of synthetic quartz with gel type water (Linker and Kirby, 1981 and Muto et al., 2011).

  17. A high performance triboelectric nanogenerator for self-powered non-volatile ferroelectric transistor memory

    NASA Astrophysics Data System (ADS)

    Fang, Huajing; Li, Qiang; He, Wenhui; Li, Jing; Xue, Qingtang; Xu, Chao; Zhang, Lijing; Ren, Tianling; Dong, Guifang; Chan, H. L. W.; Dai, Jiyan; Yan, Qingfeng

    2015-10-01

    We demonstrate an integrated module of self-powered ferroelectric transistor memory based on the combination of a ferroelectric FET and a triboelectric nanogenerator (TENG). The novel TENG was made of a self-assembled polystyrene nanosphere array and a poly(vinylidene fluoride) porous film. Owing to this unique structure, it exhibits an outstanding performance with an output voltage as high as 220 V per cycle. Meanwhile, the arch-shaped TENG is shown to be able to pole a bulk ferroelectric 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) single crystal directly. Based on this effect, a bottom gate ferroelectric FET was fabricated using pentacene as the channel material and a PMN-PT single crystal as the gate insulator. Systematic tests illustrate that the ON/OFF current ratio of this transistor memory element is approximately 103. More importantly, we demonstrate the feasibility to switch the polarization state of this FET gate insulator, namely the stored information, by finger tapping the TENG with a designed circuit. These results may open up a novel application of TENGs in the field of self-powered memory systems.We demonstrate an integrated module of self-powered ferroelectric transistor memory based on the combination of a ferroelectric FET and a triboelectric nanogenerator (TENG). The novel TENG was made of a self-assembled polystyrene nanosphere array and a poly(vinylidene fluoride) porous film. Owing to this unique structure, it exhibits an outstanding performance with an output voltage as high as 220 V per cycle. Meanwhile, the arch-shaped TENG is shown to be able to pole a bulk ferroelectric 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) single crystal directly. Based on this effect, a bottom gate ferroelectric FET was fabricated using pentacene as the channel material and a PMN-PT single crystal as the gate insulator. Systematic tests illustrate that the ON/OFF current ratio of this transistor memory element is approximately 103. More importantly, we demonstrate the

  18. Persistent photoconductivity in oxygen-ion implanted KNbO3 bulk single crystal

    NASA Astrophysics Data System (ADS)

    Tsuruoka, R.; Shinkawa, A.; Nishimura, T.; Tanuma, C.; Kuriyama, K.; Kushida, K.

    2016-12-01

    Persistent Photoconductivity (PPC) in oxygen-ion implanted KNbO3 ([001] oriented bulk single crystals; perovskite structure; ferroelectric with a band gap of 3.16 eV) is studied in air at room temperature to prevent the degradation of its crystallinity caused by the phase transition. The residual hydrogens in un-implanted samples are estimated to be 5×1014 cm-2 from elastic recoil detection analysis (ERDA). A multiple-energy implantation of oxygen ions into KNbO3 is performed using energies of 200, 400, and 600 keV (each ion fluence:1.0×1014 cm-2). The sheet resistance varies from >108 Ω/□ for an un-implanted sample to 1.9×107 Ω/□ for as-implanted one, suggesting the formation of donors due to hydrogen interstitials and oxygen vacancies introduced by the ion implantation. The PPC is clearly observed with ultraviolet and blue LEDs illumination rather than green, red, and infrared, suggesting the release of electrons from the metastable conductive state below the conduction band relating to the charge states of the oxygen vacancy.

  19. Role of crystal orientation on chemical mechanical polishing of single crystal copper

    NASA Astrophysics Data System (ADS)

    Zhu, Aibin; He, Dayong; Luo, Wencheng; Liu, Yangyang

    2016-11-01

    The material removal mechanism of single crystal copper in chemical mechanical polishing (CMP) has not been intensively investigated. And the role of crystal orientation in CMP of single crystal cooper is not quite clear yet. Quasi-continuum method was adopted in this paper to simulate the process of nano-particles grinding on single crystal copper in CMP process. Three different crystal orientations, i.e. x[100]y[001], x[001]y[110] and x[-211]y[111], were chosen for analysis. The atom displacement diagrams, stress distribution diagrams and load-displacement curves were obtained. After analyzing the deformation mechanism, residual stress of the work piece material and cutting force, results showed that, the crystal orientation of work piece has great influence on the deformation characteristics and surface quality of work piece during polishing. In the A(001)[100] orientation, the residual stress distribution after polishing is deeper, and the stress is larger than that in the B(110)[001] and C(111)[-211] orientations. And the average tangential cutting force in the A(001)[100] orientation is much larger than those in the other two crystal orientation. This research is helpful to revealing the material removal mechanism of CMP process.

  20. Roflumilast - A reversible single-crystal to single-crystal phase transition at 50 °C

    NASA Astrophysics Data System (ADS)

    Viertelhaus, Martin; Holst, Hans Christof; Volz, Jürgen; Hummel, Rolf-Peter

    2013-01-01

    Roflumilast is a selective phosphodiesterase type 4 inhibitor and is marketed under the brand names Daxas®, Daliresp® and Libertec®. A phase transition of the drug substance roflumilast was observed at 50 °C. The low temperature form, the high temperature form and the phase transition were characterised by differential scanning calorimetry, variable temperature powder X-ray diffraction and single crystal X-ray diffraction, Raman spectroscopy and solid state NMR spectroscopy. The phase transition of roflumilast at 50 °C is completely reversible, the high temperature form cannot be stabilised by quench cooling and the phase transition does not influence the quality of the active pharmaceutical ingredient (API) and the drug product. It was observed to be a single crystal to single crystal phase transition.

  1. High-quality bulk hybrid perovskite single crystals within minutes by inverse temperature crystallization

    PubMed Central

    Saidaminov, Makhsud I.; Abdelhady, Ahmed L.; Murali, Banavoth; Alarousu, Erkki; Burlakov, Victor M.; Peng, Wei; Dursun, Ibrahim; Wang, Lingfei; He, Yao; Maculan, Giacomo; Goriely, Alain; Wu, Tom; Mohammed, Omar F.; Bakr, Osman M.

    2015-01-01

    Single crystals of methylammonium lead trihalide perovskites (MAPbX3; MA=CH3NH3+, X=Br− or I−) have shown remarkably low trap density and charge transport properties; however, growth of such high-quality semiconductors is a time-consuming process. Here we present a rapid crystal growth process to obtain MAPbX3 single crystals, an order of magnitude faster than previous reports. The process is based on our observation of the substantial decrease of MAPbX3 solubility, in certain solvents, at elevated temperatures. The crystals can be both size- and shape-controlled by manipulating the different crystallization parameters. Despite the rapidity of the method, the grown crystals exhibit transport properties and trap densities comparable to the highest quality MAPbX3 reported to date. The phenomenon of inverse or retrograde solubility and its correlated inverse temperature crystallization strategy present a major step forward for advancing the field on perovskite crystallization. PMID:26145157

  2. Growth and characterization of morpholinium dihydrogenphosphate single crystal

    NASA Astrophysics Data System (ADS)

    Babu, D. Rajan; Arul, H.; Vizhi, R. Ezhil

    2016-10-01

    Morpholinium dihydrogenphosphate (MDP) single crystals were synthesized, and were subsequently grown by controlled evaporation technique at room temperature for nonlinear optical applications. The grown crystal, which belongs to the monoclinic system with the space group P21, was subjected to single crystal X-ray diffraction to confirm the structure. UV-vis-NIR spectroscopy was done on the grown crystal and it showed good optical transparency in the entire visible region with a minimum cut-off wavelength of 289 nm. The optical band gap was computed as a function of photon energy using Tauc's plot. The refractive index of the grown crystal was determined using a Metricon Prism Coupler. The thermogravimetric (TG) and differential thermal analysis (DTA) traces disclosed the thermal stability of the compound. The mechanical strength of the crystal was investigated by a Vickers microhardness tester. Dielectric constant and dielectric loss were calculated and plotted as a function of frequency at different temperatures. The second harmonic conversion efficiency was determined using the Kurtz-Perry powder technique, and the efficiency was found to be 1.2 times greater than that of standard KDP.

  3. Influence of N-H-O hydrogen bonds on the structure and properties of (K(1-x)(NH4)(x)H2PO4) proton glasses: a single crystal neutron diffraction study.

    PubMed

    Choudhury, Rajul Ranjan; Chitra, R

    2013-02-20

    It has been known for quite some time now that proton dynamics plays a key role in the structural ferroelectric (FE)/antiferroelectric (AFE) phase transition in the crystals belonging to the potassium dihydrogen phosphate crystal family. Mixed crystals belonging to this family having the composition M(1-x)(NW(4))(x)W(2)AO(4), where M = K, Rb, Cs, W = H, D, and A = P, As, exhibit proton glass behavior due to frustration between FE and AFE ordering; these proton glasses do not undergo any structural phase change but retain their room temperature structure down to very low temperatures. Single crystal neutron diffraction investigations of four mixed crystals with composition (K(1-x)(NH(4))(x)H(2)PO(4)), where x = 0.0, 0.29, 0.67 1.0, were undertaken with the intention to investigate the effect of the local structural deviations on the overall average structure of the crystals and correlate these structural changes to the presence or absence of a structural phase transition in these crystals. Hydrogen bonding is shown to play a key role in the changing nature of the mixed crystals as the composition varies from the potassium rich ferroelectric region to the proton glass region to the ammonium rich antiferroelectric region.

  4. Permanent ferroelectric retention of BiFeO3 mesocrystal

    PubMed Central

    Hsieh, Ying-Hui; Xue, Fei; Yang, Tiannan; Liu, Heng-Jui; Zhu, Yuanmin; Chen, Yi-Chun; Zhan, Qian; Duan, Chun-Gang; Chen, Long-Qing; He, Qing; Chu, Ying-Hao

    2016-01-01

    Non-volatile electronic devices based on magnetoelectric multiferroics have triggered new possibilities of outperforming conventional devices for applications. However, ferroelectric reliability issues, such as imprint, retention and fatigue, must be solved before the realization of practical devices. In this study, everlasting ferroelectric retention in the heteroepitaxially constrained multiferroic mesocrystal is reported, suggesting a new approach to overcome the failure of ferroelectric retention. Studied by scanning probe microscopy and transmission electron microscopy, and supported via the phase-field simulations, the key to the success of ferroelectric retention is to prevent the crystal from ferroelastic deformation during the relaxation of the spontaneous polarization in a ferroelectric nanocrystal. PMID:27782123

  5. Fretting Stresses in Single Crystal Superalloy Turbine Blade Attachments

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.; Swanson, Gregory

    2000-01-01

    Single crystal nickel base superalloy turbine blades are being utilized in rocket engine turbopumps and turbine engines because of their superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal nickel base turbine blade superalloys are PWA 1480/1493 and PWA 1484. These alloys play an important role in commercial, military and space propulsion systems. High Cycle Fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Blade attachment regions are prone to fretting fatigue failures. Single crystal nickel base superalloy turbine blades are especially prone to fretting damage because the subsurface shear stresses induced by fretting action at the attachment regions can result in crystallographic initiation and crack growth along octahedral planes. Furthermore, crystallographic crack growth on octahedral planes under fretting induced mixed mode loading can be an order of magnitude faster than under pure mode I loading. This paper presents contact stress evaluation in the attachment region for single crystal turbine blades used in the NASA alternate Advanced High Pressure Fuel Turbo Pump (HPFTP/AT) for the Space Shuttle Main Engine (SSME). Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. Blades and the attachment region are modeled using a large-scale 3D finite element (FE) model capable of accounting for contact friction, material orthotrophy, and variation in primary and secondary crystal orientation. Contact stress analysis in the blade attachment regions is presented as a function of coefficient of friction and primary and secondary crystal orientation, Stress results are used to discuss fretting fatigue failure analysis of SSME blades. Attachment stresses are seen to reach

  6. Photocatalytic and photoelectrochemical hydrogen production on strontium titanate single crystals

    SciTech Connect

    Wagner, F.T.; Somorjai, G.A.

    1980-01-01

    Sustained photogeneration of hydrogen was observed on metal-free as well as on platinized SrTiO/sub 3/ single crystals illuminated in aqueous alkaline electrolytes or in the presence of electrolyte films. Hydrogen evolution rates increased with electrolyte hydroxide concentration, most strongly at hydroxide concentrations above 5 N. Both stoichiometric and prereduced metal-free crystals were active for hydrogen photoproduction. No activity was observed from crystals in neutral or acidic solutions or in water vapor in the absence of a crust of a basic deliquescent compounds. Metal-free crystals appear to evolve hydrogen via a photocatalytic mechanism in which all chemistry occurs at the illuminated surface. The results allow direct comparison of the photocatalytic and photoelectrochemical processes and have implications for the development of heterogeneous photocatalysis at the gas-solid interface.

  7. Monte Carlo simulations of single crystals from polymer solutions

    NASA Astrophysics Data System (ADS)

    Zhang, Jianing; Muthukumar, M.

    2007-06-01

    A novel "anisotropic aggregation" model is proposed to simulate nucleation and growth of polymer single crystals as functions of temperature and polymer concentration in dilute solutions. Prefolded chains in a dilute solution are assumed to aggregate at a seed nucleus with an anisotropic interaction by a reversible adsorption/desorption mechanism, with temperature, concentration, and seed size being the control variables. The Monte Carlo results of this model resolve the long-standing dilemma regarding the kinetic and thermal roughenings, by producing a rough-flat-rough transition in the crystal morphology with increasing temperature. It is found that the crystal growth rate varies nonlinearly with temperature and concentration without any marked transitions among any regimes of polymer crystallization kinetics. The induction time increases with decreasing the seed nucleus size, increasing temperature, or decreasing concentration. The apparent critical nucleus size is found to increase exponentially with increasing temperature or decreasing concentration, leading to a critical nucleus diagram composed in the temperature-concentration plane with three regions of different nucleation barriers: no growth, nucleation and growth, and spontaneous growth. Melting temperatures as functions of the crystal size, heating rate, and concentration are also reported. The present model, falling in the same category of small molecular crystallization with anisotropic interactions, captures most of the phenomenology of polymer crystallization in dilute solutions.

  8. Formation of charged ferroelectric domain walls with controlled periodicity

    PubMed Central

    Bednyakov, Petr S.; Sluka, Tomas; Tagantsev, Alexander K.; Damjanovic, Dragan; Setter, Nava

    2015-01-01

    Charged domain walls in proper ferroelectrics were shown recently to possess metallic-like conductivity. Unlike conventional heterointerfaces, these walls can be displaced inside a dielectric by an electric field, which is of interest for future electronic circuitry. In addition, theory predicts that charged domain walls may influence the electromechanical response of ferroelectrics, with strong enhancement upon increased charged domain wall density. The existence of charged domain walls in proper ferroelectrics is disfavoured by their high formation energy and methods of their preparation in predefined patterns are unknown. Here we develop the theoretical background for the formation of charged domain walls in proper ferroelectrics using energy considerations and outline favourable conditions for their engineering. We experimentally demonstrate, in BaTiO3 single crystals the controlled build-up of high density charged domain wall patterns, down to a spacing of 7 μm with a predominant mixed electronic and ionic screening scenario, hinting to a possible exploitation of charged domain walls in agile electronics and sensing devices. PMID:26516026

  9. Single particle detection in CMOS compatible photonic crystal nanobeam cavities.

    PubMed

    Quan, Qimin; Floyd, Daniel L; Burgess, Ian B; Deotare, Parag B; Frank, Ian W; Tang, Sindy K Y; Ilic, Rob; Loncar, Marko

    2013-12-30

    We report the label-free detection of single particles using photonic crystal nanobeam cavities fabricated in silicon-on-insulator platform, and embedded inside microfluidic channels fabricated in poly-dimethylsiloxane (PDMS). Our system operates in the telecommunication wavelength band, thus leveraging the widely available, robust and tunable telecom laser sources. Using this approach, we demonstrated the detection of polystyrene nanoparticles with dimensions down to 12.5nm in radius. Furthermore, binding events of a single streptavidin molecule have been observed.

  10. Single crystal plasticity with bend-twist modes

    NASA Astrophysics Data System (ADS)

    Elkhodary, Khalil I.; Bakr, Mohamed A.

    2015-06-01

    In this work a formulation is proposed and computationally implemented for rate dependent single crystal plasticity, which incorporates plastic bend-twist modes that arise from dislocation density based poly-slip mechanisms. The formulation makes use of higher order continuum theory and may be viewed as a generalized micromechanics model. The formulation is then linked to the burgers and Nye tensors, showing how their material rates are derivable from a newly proposed third-rank tensor Λp, which incorporates a crystallographic description of bend-twist plasticity through selectable slip-system level constitutive laws. A simple three-dimensional explicit finite element implementation is outlined and employed in three simulations: (a) bi-crystal bending; (b) tension on a notched single crystal; and (c) the large compression of a microstructure to induce the plastic buckling of secondary phases. All simulation are transient, for computational expediency. The results shed light on the physics resulting from dynamic inhomogeneous plastic deformation.

  11. Anisotropy in the magnetic and multiferroic properties of LuFe2O4-δ single crystals with varying oxygen stoichiometry

    NASA Astrophysics Data System (ADS)

    Balakrishnan, G.; McKinnon, R. A.; Lees, M. R.

    2012-02-01

    LuFe2O4 is a multiferroic, where the origin of the ferroelectricity is attributed to electron correlations and directly linked to the charge ordering of Fe^2+ and Fe^3+ in the lattice. The multiferroic properties of this system are known to be sensitive to the oxygen stoichiometry. Large single crystals of LuFe2O4-δ with varying oxygen stoichiometry have been produced by the floating zone technique. Detailed magnetic susceptibility, dielectric constant and polarization measurements have been carried out along specific crystallographic axes of the single crystals over a wide temperature range to study the anisotropic properties. The effect of altering the Fe^2+/ Fe^3+ stochiometry on the physical properties of LuFe2O4-d is discussed.

  12. Giant room-temperature barocaloric effect and pressure-mediated electrocaloric effect in BaTiO{sub 3} single crystal

    SciTech Connect

    Liu, Yang; Wei, Jie; Janolin, Pierre-Eymeric; Infante, Ingrid C.; Dkhil, Brahim E-mail: xlou03@mail.xjtu.edu.cn; Lou, Xiaojie E-mail: xlou03@mail.xjtu.edu.cn

    2014-04-21

    Barocaloric effect in BaTiO{sub 3} single crystal is studied by a thermodynamic phenomenological model. It is demonstrated that a giant barocaloric effect can be achieved near room temperature with an adiabatic temperature change of more than 3 K and a temperature span about 50 K. As expected, the electrocaloric peak can be shifted towards room temperature by pressure. However, a slight reduction of the electrocaloric peak is found in contrast to relaxor ferroelectrics and LiNbO{sub 3}. We believe that our findings could open a potential route by combining the barocaloric effect and pressure-mediated electrocaloric effect in BaTiO{sub 3} single crystal for cooling devices.

  13. Growth, mechanical, thermal and dielectric properties of pure and doped KHP single crystal

    NASA Astrophysics Data System (ADS)

    M, Lakshmipriya.; Babu, D. Rajan; Vizhi, R. Ezhil

    2015-06-01

    L-Arginine doped potassium hydrogen phthalate and L-Histidine doped potassium hydrogen phthalate single crystals were grown by slow evaporation method at room temperature. The grown crystal crystallizes in orthorhombic system which is confirmed by single crystal XRD analysis. The grown crystals are subjected to thermal, mechanical and dielectric analysis.

  14. Conducting Ferroelectric Walls, Domain Topology, and Domain Switching Kinetics in a Hybrid Improper Ferroelectric

    NASA Astrophysics Data System (ADS)

    Cheong, Sang-Wook; Rutgers CenterEmergent Materials Team

    Charged polar interfaces such as charged ferroelectric domain walls or heterostructured interfaces of ZnO/(Zn,Mg)O and LaAlO 3 /SrTiO 3 , across which the normal component of electric polarization changes suddenly, can host large two-dimensional conduction. Charged ferroelectric domain walls can be highly conducting but energetically unfavored; however, they were found to be mysteriously abundant in hybrid improper ferroelectric (Ca,Sr) 3 Ti 2 O 7 single crystals. From the exploration of antiphase domain boundaries, which are hidden in piezoresponse force microscopy, using dark-field electron microscopy, we have explored the macroscopic topology of polarization domains and antiphase domains. We found that the macroscopic domain topology is directly responsible for the presence of charged domain walls, and is closely related with the polarization domain switching mechanism in (Ca,Sr) 3 Ti 2 O 7 . Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.

  15. Area detectors in single-crystal neutron diffraction

    NASA Astrophysics Data System (ADS)

    McIntyre, Garry J.

    2015-12-01

    The introduction of area detectors has brought about a gentle revolution in the routine application of single-crystal neutron diffractometry. Implemented first for macromolecular crystallography, electronic detectors subsequently gradually spread to chemical and physics-oriented crystallography at steady-state sources. The volumetric surveying of reciprocal space implicit in the Laue technique has required area detectors right from the start, whether using film and more recently image plates and CCD-based detectors at reactors, or scintillation detectors at spallation sources. Wide-angle volumetric data collection has extended application of neutron single-crystal diffractometry to chemical structures, sample volumes, and physical phenomena previously deemed impossible. More than 30 of the dedicated single-crystal neutron diffractometers at steady-state reactor and neutron spallation sources worldwide and accessible via peer-review proposal mechanisms are currently equipped with area detectors. Here we review the historical development of the various types of area detectors used for single crystals, discuss experimental aspects peculiar to experiments with such detectors, highlight the scientific fields where the use of area detectors has had a special impact, and forecast future developments in hardware, implementation, and software.

  16. A Study of Single Crystal Fatigue Failure Criteria

    NASA Technical Reports Server (NTRS)

    Sayyah, Tarek; Swanson, Gregory R.; Schonberg, William P.

    2000-01-01

    This paper presents the results of a study whose objective was to study the applicability of different failure equations in modeling low cycle fatigue (LCF) test data for single crystal test specimens. A total of four failure criteria were considered in this study. One of the failure equations was developed by Pratt & Whitney and is based on normal and shear strains on the primary crystallographic slip planes of the single crystal material. Other failure equations considered are based on isotropic criteria. Because these failure equations were originally developed for isotropic materials such as structural steel, they were modified to be applicable to the single crystal slip systems of the LCF specimen material. By observing how closely the various equations were able to reduce the scatter in the LCF test data, the applicability of those equations in modeling the LCF test data was assessed. It is desired to subsequently use the failure equation with the highest correlation in the development of a new single crystal failure criterion for the Alternative Turbopump Development (ATD) for the space shuttle main engine (SSME) High Pressure Fuel Turbopump (HPFTP).

  17. Transverse Mode Multi-Resonant Single Crystal Transducer

    NASA Technical Reports Server (NTRS)

    Snook, Kevin A. (Inventor); Liang, Yu (Inventor); Luo, Jun (Inventor); Hackenberger, Wesley S. (Inventor); Sahul, Raffi (Inventor)

    2015-01-01

    A transducer is disclosed that includes a multiply resonant composite, the composite having a resonator bar of a piezoelectric single crystal configured in a d(sub 32) transverse length-extensional resonance mode having a crystallographic orientation set such that the thickness axis is in the (110) family and resonance direction is the (001) family.

  18. TOPICAL REVIEW: Organic field-effect transistors using single crystals

    NASA Astrophysics Data System (ADS)

    Hasegawa, Tatsuo; Takeya, Jun

    2009-04-01

    Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20-40 cm2 Vs-1, achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps.

  19. Organic field-effect transistors using single crystals.

    PubMed

    Hasegawa, Tatsuo; Takeya, Jun

    2009-04-01

    Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20-40 cm(2) Vs(-1), achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps.

  20. Organic field-effect transistors using single crystals

    PubMed Central

    Hasegawa, Tatsuo; Takeya, Jun

    2009-01-01

    Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for ‘plastic electronics’. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20–40 cm2 Vs−1, achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps. PMID:27877287

  1. Reliability analysis of single crystal NiAl turbine blades

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan; Noebe, Ronald; Wheeler, Donald R.; Holland, Fred; Palko, Joseph; Duffy, Stephen; Wright, P. Kennard

    1995-01-01

    As part of a co-operative agreement with General Electric Aircraft Engines (GEAE), NASA LeRC is modifying and validating the Ceramic Analysis and Reliability Evaluation of Structures algorithm for use in design of components made of high strength NiAl based intermetallic materials. NiAl single crystal alloys are being actively investigated by GEAE as a replacement for Ni-based single crystal superalloys for use in high pressure turbine blades and vanes. The driving force for this research lies in the numerous property advantages offered by NiAl alloys over their superalloy counterparts. These include a reduction of density by as much as a third without significantly sacrificing strength, higher melting point, greater thermal conductivity, better oxidation resistance, and a better response to thermal barrier coatings. The current drawback to high strength NiAl single crystals is their limited ductility. Consequently, significant efforts including the work agreement with GEAE are underway to develop testing and design methodologies for these materials. The approach to validation and component analysis involves the following steps: determination of the statistical nature and source of fracture in a high strength, NiAl single crystal turbine blade material; measurement of the failure strength envelope of the material; coding of statistically based reliability models; verification of the code and model; and modeling of turbine blades and vanes for rig testing.

  2. Unified constitutive model for single crystal deformation behavior with applications

    NASA Technical Reports Server (NTRS)

    Walker, K. P.; Meyer, T. G.; Jordan, E. H.

    1988-01-01

    Single crystal materials are being used in gas turbine airfoils and are candidates for other hot section components because of their increased temperature capabilities and resistance to thermal fatigue. Development of a constitutive model which assesses the inelastic behavior of these materials has been studied in 2 NASA programs: Life Prediction and Constitutive Models for Engine Hot Section Anisotropic Materials and Biaxial Constitutive Equation Development for Single Crystals. The model has been fit to a large body of constitutive data for single crystal PWA 1480 material. The model uses a unified approach for computing total inelastic strains (creep plus plasticity) on crystallographic slip systems reproducing observed directional and strain rate effects as a natural consequence of the summed slip system quantities. The model includes several of the effects that have been reported to influence deformation in single crystal materials, such as shear stress, latent hardening, and cross slip. The model is operational in a commercial Finite Element code and is being installed in a Boundary Element Method code.

  3. Dynamic actuation of single-crystal diamond nanobeams

    SciTech Connect

    Sohn, Young-Ik; Burek, Michael J.; Lončar, Marko; Kara, Vural; Kearns, Ryan

    2015-12-14

    We show the dielectrophoretic actuation of single-crystal diamond nanomechanical devices. Gradient radio-frequency electromagnetic forces are used to achieve actuation of both cantilever and doubly clamped beam structures, with operation frequencies ranging from a few MHz to ∼50 MHz. Frequency tuning and parametric actuation are also studied.

  4. Some Debye temperatures from single-crystal elastic constant data

    USGS Publications Warehouse

    Robie, R.A.; Edwards, J.L.

    1966-01-01

    The mean velocity of sound has been calculated for 14 crystalline solids by using the best recent values of their single-crystal elastic stiffness constants. These mean sound velocities have been used to obtain the elastic Debye temperatures ??De for these materials. Models of the three wave velocity surfaces for calcite are illustrated. ?? 1966 The American Institute of Physics.

  5. Low-cost single-crystal turbine blades, volume 1

    NASA Technical Reports Server (NTRS)

    Strangman, T. E.; Heath, B.; Fujii, M.

    1983-01-01

    The exothermic casting process was successfully developed into a low cost nonproprietary method for producing single crystal (SC) castings. Casting yields were lower than expected, on the order of 20 percent, but it is felt that the casting yield could be significantly improved with minor modifications to the process. Single crystal Mar-M 247 and two derivative SC alloys were developed. NASAIR 100 and SC Alloy 3 were fully characterized through mechanical property testing. SC Mar-M 247 shows no significant improvement in strength over directionally solidified (DS) Mar-M 247, but the derivative alloys, NASAIR 100 and Alloy 3, show significant tensile and fatigue improvements. The 1000 hr/238 MPa (20 ksi) stress rupture capability compared to DS Mar-M 247 was improved over 28 C. Firtree testing, holography, and strain gauge rig testing were used to evaluate the effects of the anisotropic characteristics of single crystal materials. In general, the single crystal material behaved similarly to DS Mar-M 247. Two complete engine sets of SC HP turbine blades were cast using the exothermic casting process and fully machined.

  6. Low temperature magnetic transitions of single crystal HoBi

    SciTech Connect

    Fente, A.; Suderow, H.; Vieira, S.; Nemes, N. M.; García-Hernández, M.; Bud'ko, S. L.; Canfield, P. C.

    2013-10-01

    We present resistivity, specific heat and magnetization measurements in high quality single crystals of HoBi, with a residual resistivity ratio of 126. We find, from the temperature and field dependence of the magnetization, an antiferromagnetic transition at 5.7 K, which evolves, under magnetic fields, into a series of up to five metamagnetic phases.

  7. Microstructure tuning and magnetism switching of ferroelectric barium titanate

    SciTech Connect

    Zhou, Wenliang; Deng, Hongmei; Ding, Nuofan; Yu, Lu; Yue, Fangyu; Yang, Pingxiong; Chu, Junhao

    2015-09-15

    Single-crystal and polycrystal BaTiO{sub 3} (BTO) materials synthesized by the physical and chemical methods, respectively, have been studied based on microstructural characterizations and magnetic measurements. The results of X-ray diffraction and Raman scatting spectra show that a single crystal tetragonal to polycrystalline pseudo-cubic structure transformation occurs in BTO ferroelectrics, dependent of growth conditions and interface effects. High-resolution transmission electron microscope data indicate that the as-prepared BTO/SrTiO{sub 3} (001) and BTO/SrRuO{sub 3}/SrTiO{sub 3} (001) heterostructures are highly c-axis oriented with atomic sharp interfaces. Lattice defects (i.e., edge-type misfit dislocations and stacking faults) in the heterostructures could be identified clearly and showed tunable with the variations of interface strain. Furthermore, the effects of vacancy defects on magnetic properties of BTO are discussed, which shows a diamagnetism–ferromagnetism switching as intrinsic vacancies increase. This work opens up a possible avenue to prepare magnetic BTO ferroelectrics. - Highlights: • Structure of BTO is tunable, depending on growth conditions and interface strain. • STEM–EDX data indicate the presence of lattice defects in BTO ferroelectrics. • BTO magnetism could be controlled by defects showing dia-ferromagnetism switching. • BTO with more vacancies shows RTFM, as evidence of vacancy magnetism effects.

  8. Direct observation of the ferroelectric polarization in the layered perovskite Bi4Ti3O12

    NASA Astrophysics Data System (ADS)

    Urushihara, Daisuke; Komabuchi, Mai; Ishizawa, Nobuo; Iwata, Makoto; Fukuda, Koichiro; Asaka, Toru

    2016-10-01

    We investigated the crystal structure and ferroelectric domains of Bi4Ti3O12 (BTO) by means of transmission electron microscopy (TEM) and single-crystal X-ray diffractometry. From the extinction rule, we determined that the space group in the ferroelectric phase of BTO is P1a1 rather than B2cb and B1a1 which have been proposed previously. We successfully refined the crystal structure based on the space group P1a1. The 180° and 90° ferroelectric domain structures were observed by the [001]-zone dark-field TEM imaging. In the 180° domain structure, we determined that one component of the polarization vector is parallel to the a-axis. An annular bright-field scanning transmission electron microscopy (ABF-STEM) was performed for the direct observation of the crystal structures. The ABF-STEM images displayed the contrasts with respect to every atomic position in spite of the highly distorted structure of BTO. We could evaluate the tilting and distortion of the [TiO6] octahedra relatively. Therefore, we directly observed the ferroelectric displacements of Bi and Ti ions.

  9. Electronic states of pyrene single crystal and of its single molecule inserted in a molecular vessel of cyclodextrin

    NASA Astrophysics Data System (ADS)

    Takahashi, Nobuaki; Gombojav, Bold; Yoshinari, Takehisa; Nagasaka, Shin-ichiro; Takahashi, Yoshio; Yamamoto, Aishi; Goto, Takenari; Kasuya, Atsuo

    2004-10-01

    Highly purified single crystals of pyrene were made by a gas phase crystal growth method from 180 times of zone-refined pyrene. The absorption spectra of the single crystal have been transformed from the reflection spectra between 2.5 and 6.5 eV at 2, 77 K and room temperature. The dry powder of β-cyclodextrin including pyrene single molecule were prepared in vacuum to investigate the electronic states of the isolated molecule. The absorption spectra of the single molecule show similar spectra to those of the single crystal. The pyrene molecule keeps its electronic character even in the single crystal.

  10. Stress effects in ferroelectric perovskite thin-films

    NASA Astrophysics Data System (ADS)

    Zednik, Ricardo Johann

    The exciting class of ferroelectric materials presents the engineer with an array of unique properties that offer promise in a variety of applications; these applications include infra-red detectors ("night-vision imaging", pyroelectricity), micro-electro-mechanical-systems (MEMS, piezoelectricity), and non-volatile memory (NVM, ferroelectricity). Realizing these modern devices often requires perovskite-based ferroelectric films thinner than 100 nm. Two such technologically important material systems are (Ba,Sr)TiO3 (BST), for tunable dielectric devices employed in wireless communications, and Pb(Zr,Ti)O3 (PZT), for ferroelectric non-volatile memory (FeRAM). In general, the material behavior is strongly influenced by the mechanical boundary conditions imposed by the substrate and surrounding layers and may vary considerably from the known bulk behavior. A better mechanistic understanding of these effects is essential for harnessing the full potential of ferroelectric thin-films and further optimizing existing devices. Both materials share a common crystal structure and similar properties, but face unique challenges due to the design parameters of these different applications. Tunable devices often require very low dielectric loss as well as large dielectric tunability. Present results show that the dielectric response of BST thin-films can either resemble a dipole-relaxor or follow the accepted empirical Universal Relaxation Law (Curie-von Schweidler), depending on temperature. These behaviors in a single ferroelectric thin-film system are often thought to be mutually exclusive. In state-of-the-art high density FeRAM, the ferroelectric polarization is at least as important as the dielectric response. It was found that these properties are significantly affected by moderate biaxial tensile and compressive stresses which reversibly alter the ferroelastic domain populations of PZT at room temperature. The 90-degree domain wall motion observed by high resolution

  11. Growth and characterization of terbium fumarate heptahydrate single crystals

    NASA Astrophysics Data System (ADS)

    Want, B.; Shah, M. D.

    2014-03-01

    The growth of terbium fumarate heptahydrate single crystals was achieved by single gel diffusion technique using silica gel as a medium of growth. The effect of various growth parameters on the nucleation rate of these crystals was studied. The crystals were characterized by different physico-chemical techniques of characterization. Powder X-ray diffraction pattern showed that terbium fumarate is a crystalline compound. Fourier transform infrared spectroscopy was performed for the identification of water and other functional groups present in the compound. UV-vis and photoluminescence spectrophotometric experiments were carried out to study the optical properties of the grown crystals. Elemental analysis suggested the chemical formula of the crystals to be Tb2(C4H2O4)3·7H2O. The presence of seven molecules of water was also supported by the thermogravimetric analysis. The hydrated compound was found to be thermally stable upto a temperature of about 110 °C and its anhydrous form up to the temperature of 410 °C. The thermal decomposition of the compound in the nitrogen atmosphere leads to the formation of terbium oxide as the final product. An attempt was made to relate the experimental results with the classical nucleation theory.

  12. New Techniques in Characterization of Ferroelectric Materials

    NASA Technical Reports Server (NTRS)

    Sehirlioglu, Alp

    2008-01-01

    Two new techniques have been developed to characterize Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) based ferroelectric single crystals: (i) electro-thermal imaging, and (ii) single crystal x-ray diffraction in the transmission mode. (i) Electro-thermal imaging is a remote sensing technique that can detect the polarization direction and poling state of a whole crystal slice. This imaging technique utilizes an IR camera to determine the field induced temperature change and does not require any special or destructive sample preparation. In the resulting images it is possible to distinguish regions of 180 deg domains. This powerful technique can be used remotely during poling to determine the poling state of the crystal to avoid over-poling that can result in inferior properties and/or cracking of the crystals. Electro-thermal imaging produced the first direct observations of polarization rotation. Under bipolar field, the domains near the corners were the first to switch direction. As the field increased above the coercive field, domains at the center part of the crystals switched direction. (ii) X-ray diffraction in the transmission mode has long been used in structure determination of organic crystals and proteins; however, it is not used much to characterize inorganic systems. 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals were examined by this XRD technique for the first time, and a never-before-seen super-lattice was revealed with a doubling of the unit cell in all three directions, giving a cell volume eight times that of a traditional perovskite unit cell. The significance of the super-lattice peaks increased with poling, indicating a structural contribution to ordering. Lack of such observations by electron diffraction in the transmission electron microscope examinations suggests the presence of a bulk effect.

  13. Understanding the Cubic Phase Stabilization and Crystallization Kinetics in Mixed Cations and Halides Perovskite Single Crystals.

    PubMed

    Xie, Li-Qiang; Chen, Liang; Nan, Zi-Ang; Lin, Hai-Xin; Wang, Tan; Zhan, Dong-Ping; Yan, Jia-Wei; Mao, Bing-Wei; Tian, Zhong-Qun

    2017-03-08

    The spontaneous α-to-δ phase transition of the formamidinium-based (FA) lead halide perovskite hinders its large scale application in solar cells. Though this phase transition can be inhibited by alloying with methylammonium-based (MA) perovskite, the underlying mechanism is largely unexplored. In this Communication, we grow high-quality mixed cations and halides perovskite single crystals (FAPbI3)1-x(MAPbBr3)x to understand the principles for maintaining pure perovskite phase, which is essential to device optimization. We demonstrate that the best composition for a perfect α-phase perovskite without segregation is x = 0.1-0.15, and such a mixed perovskite exhibits carrier lifetime as long as 11.0 μs, which is over 20 times of that of FAPbI3 single crystal. Powder XRD, single crystal XRD and FT-IR results reveal that the incorporation of MA(+) is critical for tuning the effective Goldschmidt tolerance factor toward the ideal value of 1 and lowering the Gibbs free energy via unit cell contraction and cation disorder. Moreover, we find that Br incorporation can effectively control the perovskite crystallization kinetics and reduce defect density to acquire high-quality single crystals with significant inhibition of δ-phase. These findings benefit the understanding of α-phase stabilization behavior, and have led to fabrication of perovskite solar cells with highest efficiency of 19.9% via solvent management.

  14. Microwave Induced Direct Bonding of Single Crystal Silicon Wafers

    NASA Technical Reports Server (NTRS)

    Budraa, N. K.; Jackson, H. W.; Barmatz, M.

    1999-01-01

    We have heated polished doped single-crystal silicon wafers in a single mode microwave cavity to temperatures where surface to surface bonding occurred. The absorption of microwaves and heating of the wafers is attributed to the inclusion of n-type or p-type impurities into these substrates. A cylindrical cavity TM (sub 010) standing wave mode was used to irradiate samples of various geometry's at positions of high magnetic field. This process was conducted in vacuum to exclude plasma effects. This initial study suggests that the inclusion of impurities in single crystal silicon significantly improved its microwave absorption (loss factor) to a point where heating silicon wafers directly can be accomplished in minimal time. Bonding of these substrates, however, occurs only at points of intimate surface to surface contact. The inclusion of a thin metallic layer on the surfaces enhances the bonding process.

  15. Spatially resolved micro-photoluminescence imaging of porphyrin single crystals

    NASA Astrophysics Data System (ADS)

    Marin, Dawn M.; Castaneda, Jose; Kaushal, Meesha; Kaouk, Ghallia; Jones, Daniel S.; Walter, Michael G.

    2016-08-01

    We describe the collection of both time-resolved and steady-state micro-photoluminescence data from solution-grown single crystals of 5,15-bis(4-carbomethoxyphenyl)porphyrin (BCM2PP). Linking molecular orientation and structure with excited-state dynamics is crucial for engineering efficient organic solar cells, light-emitting diodes, and related molecular electronics. Photoluminescence features of single porphyrin crystals were imaged using a laser scanning confocal microscope equipped with time-correlated single photon counting (TCSPC). We show enhanced exciton lifetimes (τs1 = 2.6 ns) and stronger steady-state emission in crystalline BCM2PP samples relative to semicrystalline thin films (τs1 = 1.8 ns).

  16. Differences between individual ZSM-5 crystals in forming hollow single crystals and mesopores during base leaching.

    PubMed

    Fodor, Daniel; Krumeich, Frank; Hauert, Roland; van Bokhoven, Jeroen A

    2015-04-13

    After base treatment of ZSM-5 crystals below 100 nm in size, TEM shows hollow single crystals with a 10 nm shell. SEM images confirm that the shell is well- preserved even after prolonged treatment. Determination of the Si/Al ratios with AAS and XPS in combination with argon sputtering reveals aluminum zoning of the parent zeolite, and the total pore volume increases in the first two hours of base treatment. In corresponding TEM images, the amount of hollow crystals are observed to increase during the first two hours of base treatment, and intact crystals are visible even after 10 h of leaching; these observations indicate different dissolution rates between individual crystals. TEM of large, commercially available ZSM-5 crystals shows inhomogeneous distribution of mesopores among different crystals, which points to the existence of structural differences between individual crystals. Only tetrahedrally coordinated aluminum is detected with (27) Al MAS NMR after the base leaching of nano-sized ZSM-5.

  17. Single crystal growth and anisotropic crystal-fluid interfacial free energy in soft colloidal systems.

    PubMed

    Nguyen, Van Duc; Hu, Zhibing; Schall, Peter

    2011-07-01

    We measure the anisotropy of the crystal-fluid interfacial free energy in soft colloidal systems. A temperature gradient is used to direct crystal nucleation and control the growth of large single crystals in order to achieve well-equilibrated crystal-fluid interfaces. Confocal microscopy is used to follow both the growth process and the equilibrium crystal-fluid interface at the particle scale: heterogeneous crystal nucleation, the advancing interface, and the stationary equilibrium interface. We use the measured growth velocity to determine the chemical potential difference between crystal and fluid phases. Well-equilibrated, large crystal-fluid interfaces are then used to determine the interfacial free energy and its anisotropy directly from thermally excited interface fluctuations. We find that while the measured average interfacial free energy is in good agreement with values found in simulations, the anisotropy is significantly larger than simulation values. Finally, we investigate the effect of impurities on the advancing interface. We determine the critical force needed to overcome impurity particles from the local interface curvature.

  18. Plastic Deformation of O+ Oriented Quartz Single Crystals

    NASA Astrophysics Data System (ADS)

    Poston, E. J.; Holyoke, C. W., III; Kronenberg, A. K.

    2015-12-01

    The strength of wet quartz deforming by dislocation creep significantly influences the strength of mid to lower crust. Dislocation creep of quartz in Earth's crust is dominated by slip on the basal slip system. However, very little is known about the temperature, strain rate, or water fugacity dependence of this slip system. In order to better understand the rheology of the basal slip system, we deformed single crystals of synthetic quartz, with the basal slip system oriented at 45° to the compression direction (O+ orientation). Each core was annealed at 900°C and 1 atm for 24 hours to convert the gel-type water defects found in synthetic quartz into fluid inclusions, like those observed in milky quartz. FTIR analysis indicate that water contents (200-450 H/106Si) were not affected by the annealing process. The annealed single crystals were then deformed in a Griggs piston-cylinder rock deformation apparatus using a solid salt assembly, at temperatures from 800 to 900°C, strain rates from 10-6 to 10-4/s, and a confining pressure of 1.5 GPa. The strength of the quartz crystals increases with faster strain rates and decreases with increasing temperature. During some of the faster strain rate steps at 800°C, the crystals did not deform plastically before the differential stress reached the confining pressure, whereas they deformed at low stresses at 800°C and 10-6/s. The microstructures visible in the deformed samples are consistent with dislocation creep. The samples exhibit undulatory extinction, and show no deformation lamellae or subgrain formation. The strength of synthetic quartz crystals with low water contents deformed in this study is greater than milky quartz single crystals with high water contents deformed at the same conditions in other studies. These results indicate that the strength of basal slip system in quartz is affected by both water content and water fugacity.

  19. Subsurface Stress Fields In Single Crystal (Anisotropic) Contacts

    NASA Technical Reports Server (NTRS)

    Arakere, Nagaraj K.; Knudsen, Erik C.; Duke, Greg; Battista, Gilda; Swanson, Greg

    2004-01-01

    Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent HCF failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and noncrystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is , presented, for evaluating the subsurface stresses in the elastic half-space, using a complex potential method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis. Effects of crystal orientation on stress response and fatigue life are examined.

  20. Mechanism of the emergence of the photo-EMF upon silicon liquid crystal-single crystal contact

    NASA Astrophysics Data System (ADS)

    Budagov, K. M.; Guseinov, A. G.; Pashaev, B. G.

    2017-03-01

    The effect light has on a silicon liquid crystal-single crystal contact at different temperatures of the surface doping of silicon, and when BaTiO3 nanoparticles are added to the composition of a liquid crystal, is studied. The mechanism of the emergence of the photo-EMF in the liquid crystal-silicon structure is explained.