Switching characteristics of (Bi 1/2Na 1/2)TiO 3-BaTiO 3-(Bi 1/2K 1/2)TiO 3 lead-free ferroelectric ceramics

NASA Astrophysics Data System (ADS)

Shieh, J.; Wu, K. C.; Chen, C. S.

2007-04-01

The polarization switching characteristics of lead-free a(Bi 1/2Na 1/2)TiO 3-bBaTiO 3-c(Bi 1/2K 1/2)TiO 3 (abbreviated as BNBK 100a/100b/100c) ferroelectric ceramics are investigated. This is achieved through examining their polarization and strain hystereses inside and outside the morphotropic phase boundary (MPB). The total induced electrostrain (ɛ 33,total) and apparent piezoelectric charge coefficient (d 33) first increase dramatically and then decrease gradually as the BNBK composition moves from the tetragonal phase to the MPB and then to the rhombohedral phase. The measured polarization hystereses indicate that the BNBK compositions situated near the rhombohedral side of the MPB typically possess higher coercive field (E c) and remanent polarization (P r), while the compositions situated near the tetragonal side of the MPB possess higher apparent permittivity. Adverse effects on the ferroelectric properties are observed when BNBK is doped with donor dopants such as La and Nb. On the contrary, intricate hysteresis behaviors are observed when acceptor dopant Mn is introduced into BNBK. Under an alternating electric field of +/-5.0 MVm -1, BNBK 85.4/2.6/12, a composition well within the MPB, exhibits an ɛ 33,total of ~0.14%, an apparent d 33 of 295 pCN -1, an E c of 2.5 MVm -1 and a Pr of 22.5 μCcm -2. These notable ferroelectric property values suggest a candidate material for lead-free actuator applications. The present study provides a systematic set of hysteresis measurements which can be used to characterize the switching behaviors of BNBK-based lead-free ferroelectrics.

Quench hardening of Sb0.2 Bi1.8Te3, Bi2Te2.8Se0.2 and Sn0.2 Bi1.8Te3 single crystals

NASA Astrophysics Data System (ADS)

Soni, P. H.

2018-02-01

The V2-VI3 intermetallics are narrow band gap semiconductors and well known for their thermoelectric properties. They therefore offer a convenient route to tune band gap for manipulating thermoelectric parameters. The V group element Sb can be fruitfully used to substitute Bi in various proportions thus forming a psuedobinary solid solution. The electronic in general and the thermoelectric properties in particular of this psuedobinary have been amply reported. However there are no reports found on mechanical properties. I have used Sb0.2 Bi1.8Te3, Bi2Te2.8Se0.2 and Sn0.2 Bi1.8Te3single crystals grown using Bridgman technique for the quenching treatment followed by hardness testing. Vickers hardness tests were conducted on the cleavage planes of the crystals quenched from various high temperatures and the quench hardenening coefficient values have been determined. The hardness tests were carried out at various applied loads also to explore load dependence of the measured hardness. The results are reported in the paper.

Hierarchical domain structure of lead-free piezoelectric (Na{sub 1/2} Bi{sub 1/2})TiO{sub 3}-(K{sub 1/2} Bi{sub 1/2})TiO{sub 3} single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Chengtao, E-mail: lchentao@vt.edu; Wang, Yaojin; Ge, Wenwei

2016-05-07

We report a unique hierarchical domain structure in single crystals of (Na{sub 1/2}Bi{sub 1/2})TiO{sub 3}-xat. %(K{sub 1/2}Bi{sub 1/2})TiO{sub 3} for x = 5 and 8 by transmission electron microscopy (TEM). A high density of polar nano-domains with a lamellar morphology was found, which were self-assembled into a quadrant-like configuration, which then assembled into conventional ferroelectric macro-domains. Studies by high resolution TEM revealed that the polar lamellar regions contained a coexistence of in-phase and anti-phase oxygen octahedral tilt regions of a few nanometers in size. Domain frustration over multiple length scales may play an important role in the stabilization of the hierarchy, andmore » in reducing the piezoelectric response of this Pb-free piezoelectric solid solution.« less

Thermoelectric properties of Te doped bulk Bi2Se3 system

NASA Astrophysics Data System (ADS)

Adam, A. M.; Elshafaie, A.; Mohamed, Abd El-Moez A.; Petkov, P.; Ibrahim, E. M. M.

2018-03-01

Polycrystalline bulk samples of Bi2(Se1‑xTex)3 system with x = 0.0–0.9 were prepared by the conventional melting method. Successfully and cheaply, Se atoms were replaced by Te atoms to get Bi2Se3-Bi2Te3 or even Bi2Te3 alone. Difference of mass and size between Te and Se atoms is expected to result in interesting properties in the Bi2(Se1‑xTex)3 system. All compounds showed a metal-semiconductor conductivity transition. The electrical conduction in the pristine Bi2Se3 compound increases with the low Te doping ratio (x = 0.3) then decreases monotonically for further amounts of Te. The Seebeck coefficient of Bi2Se3 compound is positive showing up a p-type conduction. However, introducing Te content increases the n-type conduction with a decrease in the Seebeck coefficient absolute value. In addition, Bi2Se3 compound is found to exhibit relatively high room temperature power factor and figure of merit values of 2.13 μW/m.k2. In an attempt to determine the figure of merit ZT, Bi2Se3 seems to be the best for room temperature, whereas, Te addition at high values makes the system just suitable for high temperature application.

Electric field induced lattice strain in pseudocubic Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3}-modified BaTiO{sub 3}-BiFeO{sub 3} piezoelectric ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fujii, Ichiro, E-mail: ifujii@rins.ryukoku.ac.jp; Iizuka, Ryo; Ueno, Shintaro

2016-04-25

Contributions to the piezoelectric response in pseudocubic 0.3BaTiO{sub 3}-0.1Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3}-0.6BiFeO{sub 3} ceramics were investigated by synchrotron X-ray diffraction under electric fields. All of the lattice strain determined from the 110, 111, and 200 pseudocubic diffraction peaks showed similar lattice strain hysteresis that was comparable to the bulk butterfly-like strain curve. It was suggested that the hysteresis of the lattice strain and the lack of anisotropy were related to the complex domain structure and the phase boundary composition.

Spin polarized surface resonance bands in single layer Bi on Ge(1 1 1)

NASA Astrophysics Data System (ADS)

Bottegoni, F.; Calloni, A.; Bussetti, G.; Camera, A.; Zucchetti, C.; Finazzi, M.; Duò, L.; Ciccacci, F.

2016-05-01

The spin features of surface resonance bands in single layer Bi on Ge(1 1 1) are studied by means of spin- and angle-resolved photoemission spectroscopy and inverse photoemission spectroscopy. We characterize the occupied and empty surface states of Ge(1 1 1) and show that the deposition of one monolayer of Bi on Ge(1 1 1) leads to the appearance of spin-polarized surface resonance bands. In particular, the C 3v symmetry, which Bi adatoms adopt on Ge(1 1 1), allows for the presence of Rashba-like occupied and unoccupied electronic states around the \\overline{\\text{M}} point of the Bi surface Brillouin zone with a giant spin-orbit constant |{α\\text{R}}| =≤ft(1.4+/- 0.1\\right) eV · Å.

Growth and magnetic properties of multiferroic LaxBi1-xMnO3 thin films

NASA Astrophysics Data System (ADS)

Gajek, M.; Bibes, M.; Wyczisk, F.; Varela, M.; Fontcuberta, J.; Barthélémy, A.

2007-05-01

A comparative study of LaxBi1-xMnO3 thin films grown on SrTiO3 substrates is reported. It is shown that these films grow epitaxially in a narrow pressure-temperature range. A detailed structural and compositional characterization of the films is performed within the growth window. The structure and the magnetization of this system are investigated. We find a clear correlation between the magnetization and the unit-cell volume that we ascribe to Bi deficiency and the resultant introduction of a mixed valence on the Mn ions. On these grounds, we show that the reduced magnetization of LaxBi1-xMnO3 thin films compared to the bulk can be explained quantitatively by a simple model, taking into account the deviation from nominal composition and the Goodenough-Kanamori-Anderson rules of magnetic interactions.

Ferroelectric and magnetic properties of Aurivillius Bi{sub m+1}Ti{sub 3}Fe{sub m−3}O{sub 3m+3} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jia, Tingting, E-mail: jia.tingting@nims.go.jp; Kimura, Hideo, E-mail: KIMURA.Hideo@nims.go.jp; Cheng, Zhenxiang

2015-11-15

Aurivillius Bi{sub m+1}Ti{sub 3}Fe{sub m−3}O{sub 3m+3} (m = 4, 5, 6) thin films have been deposited by a pulsed laser deposition system. The x-ray diffraction patterns indicate the formation of orthorhombic phase. The remanent polarization (2P{sub r}) of Bi{sub m+1}Ti{sub 3}Fe{sub m−3}O{sub 3m+3} thin films is decreased with the m-number. Positive-up-negative-down measurements indicate the presence of ferroelectric (FE) polarization in as-obtained thin films. Piezoresponse force microscopy investigations confirm the existence of FE domains and the switchable polarization. Weak magnetic moment is detected in the Aurivillius films at room temperature. The present work suggests the possibility of Aurivillius Bi{sub m+1}Ti{sub 3}Fe{sub m−3}O{sub 3m+3}more » (m = 4, 5, 6) materials as potential room-temperature multiferroics.« less

Thermal conductivity of Bi2(SexTe1-x)3 alloy films grown by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Yoo, Taehee; Lee, Eungkyu; Dong, Sining; Li, Xiang; Liu, Xinyu; Furdyna, Jacek K.; Dobrowolska, Margaret; Luo, Tengfei

2017-06-01

We studied the thermal conductivity of Bi2Se3, Bi2Te3, and their alloy Bi2(SexTe1-x)3 at room temperature using time-domain thermoreflectance measurements. The Bi2(SexTe1-x)3 films with various concentrations of Se and Te prepared by molecular beam epitaxy on GaAs substrates were investigated to study the dependence of thermal conductivity on film composition. We observed that the Bi2(SexTe1-x)3 ternary alloys can have much lower thermal conductivity values compared to those of Bi2Se3 and Bi2Te3. These results may provide useful information for developing and engineering low thermal conductivity materials for thermoelectric applications.

Perovskite-based heterostructures integrating ferromagnetic-insulating La0.1Bi0.9MnO3

NASA Astrophysics Data System (ADS)

Gajek, M.; Bibes, M.; Barthélémy, A.; Varela, M.; Fontcuberta, J.

2005-05-01

We report on the growth of thin films and heterostructures of the ferromagnetic-insulating perovskite La0.1Bi0.9MnO3. We show that the La0.1Bi0.9MnO3 perovskite grows single phased, epitaxially, and with a single out-of-plane orientation either on SrTiO3 substrates or onto strained La2/3Sr1/3MnO3 and SrRuO3 ferromagnetic-metallic buffer layers. We discuss the magnetic properties of the La0.1Bi0.9MnO3 films and heterostructures in view of their possible potential as magnetoelectric or spin-dependent tunneling devices.

Tunable band gap in Bi(Fe1-xMnx)O3 films

NASA Astrophysics Data System (ADS)

Xu, X. S.; Ihlefeld, J. F.; Lee, J. H.; Ezekoye, O. K.; Vlahos, E.; Ramesh, R.; Gopalan, V.; Pan, X. Q.; Schlom, D. G.; Musfeldt, J. L.

2010-05-01

In order to investigate band gap tunability in polar oxides, we measured the optical properties of a series of Bi(Fe1-xMnx)O3 thin films. The absorption response of the mixed metal solid solutions is approximately a linear combination of the characteristics of the two end members, a result that demonstrates straightforward band gap tunability in this system.

Effect of Bi(Mg1/2Ti1/2)O3 addition on the electrical properties of Si-Mn modified on SrTiO3

NASA Astrophysics Data System (ADS)

Roh, Yoon-ah; Masaki, Takaki; Yoon, Dae-Ho

2015-05-01

Single-Crystalline Strontium titanate (SrTiO3) has been widely used in many fields such as catalyst, semiconductors and dielectrics. SrTiO3 is a typical perovskite-type oxide, the physical properties of which strongly depend on its chemical composition, structure, shape, size, and crystallinity. In this work, the effects of Bi(Mg1/2Ti1/2)O3 addition on the nanostructure and the dielectric properties of Si-Mn modified SrTiO3 were investigated to develop nano-sized particles and low-temperature-fired SrTiO3-based ceramics with stable temperature characteristics. The dielectric constant of SrTiO3-Bi(Mg1/2Ti1/2)O3 was found to range from 900 to 1200 at 1 kHz for samples sintered at 1200°C. This new composition, SrTiO3-Bi(Mg1/2Ti1/2)O3, can be applied as a nano-sized dielectric materials in various fields.

High Curie temperature Bi(1.85)Mn(0.15)Te3 nanoplates.

PubMed

Cheng, Lina; Chen, Zhi-Gang; Ma, Song; Zhang, Zhi-dong; Wang, Yong; Xu, Hong-Yi; Yang, Lei; Han, Guang; Jack, Kevin; Lu, Gaoqing Max; Zou, Jin

2012-11-21

Bi(1.85)Mn(0.15)Te(3) hexagonal nanoplates with a width of ~200 nm and a thickness of ~20 nm were synthesized using a solvothermal method. According to the structural characterization and compositional analysis, the Mn(2+) and Mn(3+) ions were found to substitute Bi(3+) ions in the lattice. High-level Mn doping induces significant lattice distortion and decreases the crystal lattice by 1.07% in the a axis and 3.18% in the c axis. A high ferromagnetic state with a Curie temperature of ~45 K is observed in these nanoplates due to Mn(2+) and Mn(3+) ion doping, which is a significant progress in the field of electronics and spintronics.

Structure Evolution and Multiferroic Properties in Cobalt Doped Bi4NdTi3Fe1-xCoxO15-Bi3NdTi2Fe1-xCoxO12-δ Intergrowth Aurivillius Compounds

PubMed Central

Zhang, D. L.; Huang, W. C.; Chen, Z. W.; Zhao, W. B.; Feng, L.; Li, M.; Yin, Y. W.; Dong, S. N.; Li, X. G.

2017-01-01

Here, we report the structure evolution, magnetic and ferroelectric properties in Co-doped 4- and 3-layered intergrowth Aurivillius compounds Bi4NdTi3Fe1-xCoxO15-Bi3NdTi2Fe1-xCoxO12-δ. The compounds suffer a structure evolution from the parent 4-layered phase (Bi4NdTi3FeO15) to 3-layered phase (Bi3NdTi2CoO12-δ) with increasing cobalt doping level from 0 to 1. Meanwhile the remanent magnetization and polarization show opposite variation tendencies against the doping level, and the sample with x = 0.3 has the largest remanent magnetization and the smallest polarization. It is believed that the Co concentration dependent magnetic properties are related to the population of the Fe3+ -O-Co3+ bonds, while the suppressed ferroelectric polarization is due to the enhanced leakage current caused by the increasing Co concentration. Furthermore, the samples (x = 0.1–0.7) with ferromagnetism show magnetoelectric coupling effects at room temperature. The results indicate that it is an effective method to create new multiferroic materials through modifying natural superlattices. PMID:28272495

Intrinsic Topological Insulator Bi1.5Sb0.5Te3-xSex Thin Crystals

NASA Astrophysics Data System (ADS)

Wang, Wei; Li, Li; Zou, Wenqin; He, Liang; Song, Fengqi; Zhang, Rong; Wu, Xiaoshan; Zhang, Fengming

2015-01-01

The quaternary topological insulator (Bi,Sb)2(Te,Se)3 has demonstrated topological surface states with an insulating bulk. Scientists have identified an optimized composition of Bi1.5Sb0.5Te1.7Se1.3 with the highest resistivity reported. But the physics that drive to this composition remains unclear. Here we report the crystal structure and the magneto-transport properties of Bi1.5Sb0.5Te3-xSex (BSTS) series. A correlation between the structure and the physical properties has been revealed. We found out that within the rhombohedral structure, the composition with most Te substituting Se has the highest resistivity. On the other hand, segregation of other composition phases will introduce much higher bulk concentration.

Interband absorption edge in the topological insulators Bi2(Te1-xSex) 3

NASA Astrophysics Data System (ADS)

Dubroka, A.; Caha, O.; Hronček, M.; Friš, P.; Orlita, M.; Holý, V.; Steiner, H.; Bauer, G.; Springholz, G.; Humlíček, J.

2017-12-01

We have investigated the optical properties of thin films of topological insulators Bi2Te3 , Bi2Se3 , and their alloys Bi2(Te1-xSex) 3 on BaF2 substrates by a combination of infrared ellipsometry and reflectivity in the energy range from 0.06 to 6.5 eV. For the onset of interband absorption in Bi2Se3 , after the correction for the Burstein-Moss effect, we find the value of the direct band gap of 215 ±10 meV at 10 K. Our data support the picture that Bi2Se3 has a direct band gap located at the Γ point in the Brillouin zone and that the valence band reaches up to the Dirac point and has the shape of a downward-oriented paraboloid, i.e., without a camel-back structure. In Bi2Te3 , the onset of strong direct interband absorption at 10 K is at a similar energy of about 200 meV, with a weaker additional feature at about 170 meV. Our data support the recent G W band-structure calculations suggesting that the direct interband transition does not occur at the Γ point but near the Z -F line of the Brillouin zone. In the Bi2(Te1-xSex) 3 alloy, the energy of the onset of direct interband transitions exhibits a maximum near x =0.3 (i.e., the composition of Bi2Te2Se ), suggesting that the crossover of the direct interband transitions between the two points in the Brillouin zone occurs close to this composition.

Composition-driven magnetic and structural phase transitions in Bi1-xPrxFe1-xMnxO3 multiferroics

NASA Astrophysics Data System (ADS)

Khomchenko, V. A.; Ivanov, M. S.; Karpinsky, D. V.; Paixão, J. A.

2017-09-01

Magnetic ferroelectrics continue to attract much attention as promising multifunctional materials. Among them, BiFeO3 is distinguished by exceptionally high transition temperatures and, thus, is considered as a prototype room-temperature multiferroic. Since its properties are known to be strongly affected by chemical substitution, recognition of the doping-related factors determining the multiferroic behavior of the material would pave the way towards designing the structures with enhanced magnetoelectric functionality. In this paper, we report on the crystal structure and magnetic and local ferroelectric properties of the Bi1-xPrxFe1-xMnxO3 (x ≤ 0.3) compounds prepared by a solid state reaction method. The polar R3c structure specific to the parent BiFeO3 has been found to be unstable with respect to doping for x ≳ 0.1. Depending on the Pr/Mn concentration, either the antipolar PbZrO3-like or nonpolar PrMnO3-type structure can be observed. It has been shown that the non-ferroelectric compounds are weak ferromagnetic with the remanent/spontaneous magnetization linearly decreasing with an increase in x. The samples containing the polar R3c phase exhibit a mixed antiferromagnetic/weak ferromagnetic behavior. The origin of the magnetic phase separation taking place in the ferroelectric phase is discussed as related to the local, doping-introduced structural heterogeneity contributing to the suppression of the cycloidal antiferromagnetic ordering characteristic of the pure BiFeO3.

Ba0.06(Na,Bi)0.94Ti1-x(Ni1/3Nb2/3)xO3 ceramics: X-ray diffraction and infrared spectroscopy studies

NASA Astrophysics Data System (ADS)

Mishra, R. K.; Prasad, Ashutosh; Chandra, K. P.; Prasad, K.

2018-05-01

Non-lead ceramic samples of Ba0.06(Na0.5Bi0.5)0.94Ti1-x(Ni1/3Nb2/3)xO3; 0 ≤ x ≤ 1.0 were prepared by standard high temperature ceramic synthesis method. Rietveld refinements of X-ray diffraction data of these ceramics were carried out using FullProf software and determined their crystal symmetry, space group and unit cell dimensions. Rietveld refinement revealed that Ba0.06(Na0.5Bi0.5)0.94TiO3 has a monoclinic structure with space group P4/m while B0.06(Na0.5Bi0.5)0.94(Ni1/3Nb2/3)O3 has tetragonal (pseudo-cubic) structure with space group P4/mmm. Partial replacement of Ti4+ ion by pseudo-cation (Ni1/33 +Nb2/3 5 +) 4 + resulted in the change of unit cell structure from monoclinic to tetragonal. SEM studies were carried out in order to access the quality of the prepared ceramics which showed a change in grain sizes with the increase of (Ni1/33 +Nb2/3 5 +) 4 + content. FTIR spectra confirmed the formation of perovskite type solid solutions.

Fe-Doping Effect on Thermoelectric Properties of p-Type Bi0.48Sb1.52Te3

PubMed Central

Mun, Hyeona; Lee, Kyu Hyoung; Kim, Suk Jun; Kim, Jong-Young; Lee, Jeong Hoon; Lim, Jae-Hong; Park, Hee Jung; Roh, Jong Wook; Kim, Sung Wng

2015-01-01

The substitutional doping approach has been shown to be an effective strategy to improve ZT of Bi2Te3-based thermoelectric raw materials. We herein report the Fe-doping effects on electronic and thermal transport properties of polycrystalline bulks of p-type Bi0.48Sb1.52Te3. After a small amount of Fe-doping on Bi/Sb-sites, the power factor could be enhanced due to the optimization of carrier concentration. Additionally, lattice thermal conductivity was reduced by the intensified point-defect phonon scattering originating from the mass difference between the host atoms (Bi/Sb) and dopants (Fe). An enhanced ZT of 1.09 at 300 K was obtained in 1.0 at% Fe-doped Bi0.48Sb1.52Te3 by these synergetic effects. PMID:28787981

A new ferroelectric solid solution system of LaCrO 3-BiCrO 3

NASA Astrophysics Data System (ADS)

Chen, J. I. L.; Kumar, M. Mahesh; Ye, Z.-G.

2004-04-01

A new perovskite solid solution system of (1- x)LaCrO 3- xBiCrO 3 has been prepared by conventional solid-state reaction and sintering processes at 1200°C in a sealed Pt tube or a Bi 2O 3-rich environment. A clean orthorhombic phase of LaCrO 3-type structure is established at room temperature for compositions with 0⩽ x⩽0.35. The relative density, lattice parameters, sintering mechanism, microstructure and ferroelectricity of the compounds are investigated. The substitution of Bi 2O 3 for La 2O 3 is found to decrease the unit cell volume and increase the grain size of the ceramics. The relative density of the ceramics sintered at 1200°C is significantly improved from 40% for LaCrO 3 up to about 90% for La 0.65Bi 0.35CrO 3 through a liquid phase sintering mechanism. The ferroelectricity is revealed in La 1- xBi xCrO 3 with 0.1⩽ x⩽0.35 by dielectric hysteresis loops displayed at 77 K. The remnant polarization is found to increase with increasing Bi 3+ content. The origin of the ferroelectricity is attributed to the structural distortion induced by the stereochemically active Bi 3+ ion on the A site.

Electrical conduction and thermoelectric properties of perovskite-type BaBi1-xSbxO3

NASA Astrophysics Data System (ADS)

Yasukawa, Masahiro; Shiga, Yuta; Kono, Toshio

2012-06-01

To elucidate the thermoelectric properties at high temperatures, the electrical conductivity and Seebeck coefficient were measured at temperatures between 423 K and 973 K for perovskite-type ceramics of BaBi1-xSbxO3 solid solutions with x=0.0-0.5. All the ceramics exhibit p-type semiconducting behaviors and electrical conduction is attributed to hopping of small polaronic holes localized on the pentavalent cations. Substitution of Bi with Sb causes the electrical conductivity σ and cell volume to decrease, but the Seebeck coefficient S to increase, suggesting that the Sb atoms are doped as Sb5+ and replace Bi5+, reducing 6s holes conduction from Bi5+(6s0) to Bi3+ (6s2). The thermoelectric power factor S2σ has values of 6×10-8-3×10-5 W m-1 K-2 in the measured temperature range, and is maximized for an Sb-undoped BaBiO3-δ, but decreases upon Sb doping due to the decreased σ values.

Interfacial coupling in multiferroic BiFeO3 and ferromagnetic La2/3Sr1/3MnO3 thin films

NASA Astrophysics Data System (ADS)

Dominguez, C.; E Ordoñez, J.; E Gomez, M.

2017-12-01

Antiferromagnetic/Ferromagnetic coupling mechanics have been studying by growing successfully BiFeO3/La2/3Sr1/3MnO3 bilayers on SrTiO3 single crystals by using rf and dc sputtering technique at pure oxygen pressures. We have investigated the magnetic behaviour of this samples, field cooling loops evidence interfacial coupling effect when antiferromagnetic ferroelectric BiFeO3 is placed in contact with ferromagnetic La2/3Sr1/3MnO3 indicate by the shift of the magnetization loop to negative values of the applied magnetic field. Our samples exhibited an exchange bias of 76Oe at 5K after field cooling the sample under 5000Oe. Temperature dependence of the exchange bias field showed exponential decay. The BFO/LSMO bilayer exhibits excellent ferroelectric behaviour (Ps=65μC/cm2 at 4V and 100Hz). Coexistence of ferroelectric and ferromagnetic properties in the BFO/LSMO bilayer make it a promising candidate system for applications where the magnetoelectric behaviour is required.

Superconducting and normal-state anisotropy of the doped topological insulator Sr 0.1Bi 2Se 3

DOE PAGES

Smylie, M. P.; Willa, K.; Claus, H.; ...

2018-05-16

Sr xBi 2Se 3 and the related compounds Cu xBi 2Se 3 and Nb xBi 2Se 3 have attracted considerable interest, as these materials may be realizations of unconventional topological superconductors. Superconductivity with T c ~3 K in Sr xBi 2Se 3 arises upon intercalation of Sr into the layered topological insulator Bi 2Se 3. Here we elucidate the anisotropy of the normal and superconducting state of Sr 0.1Bi 2Se 3 with angular dependent magnetotransport and thermodynamic measurements. High resolution x-ray diffraction studies underline the high crystalline quality of the samples. We demonstrate that the normal state electronic and magneticmore » properties of Sr 0.1Bi 2Se 3 are isotropic in the basal plane while we observe a large two-fold in-plane anisotropy of the upper critical field in the superconducting state. In conclusion, our results support the recently proposed odd-parity nematic state characterized by a nodal gap of Eu symmetry in Sr xBi 2Se 3.« less

Superconducting and normal-state anisotropy of the doped topological insulator Sr 0.1Bi 2Se 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smylie, M. P.; Willa, K.; Claus, H.

Sr xBi 2Se 3 and the related compounds Cu xBi 2Se 3 and Nb xBi 2Se 3 have attracted considerable interest, as these materials may be realizations of unconventional topological superconductors. Superconductivity with T c ~3 K in Sr xBi 2Se 3 arises upon intercalation of Sr into the layered topological insulator Bi 2Se 3. Here we elucidate the anisotropy of the normal and superconducting state of Sr 0.1Bi 2Se 3 with angular dependent magnetotransport and thermodynamic measurements. High resolution x-ray diffraction studies underline the high crystalline quality of the samples. We demonstrate that the normal state electronic and magneticmore » properties of Sr 0.1Bi 2Se 3 are isotropic in the basal plane while we observe a large two-fold in-plane anisotropy of the upper critical field in the superconducting state. In conclusion, our results support the recently proposed odd-parity nematic state characterized by a nodal gap of Eu symmetry in Sr xBi 2Se 3.« less

Superconducting and normal-state anisotropy of the doped topological insulator Sr0.1Bi2Se3.

PubMed

Smylie, M P; Willa, K; Claus, H; Koshelev, A E; Song, K W; Kwok, W-K; Islam, Z; Gu, G D; Schneeloch, J A; Zhong, R D; Welp, U

2018-05-16

Sr x Bi 2 Se 3 and the related compounds Cu x Bi 2 Se 3 and Nb x Bi 2 Se 3 have attracted considerable interest, as these materials may be realizations of unconventional topological superconductors. Superconductivity with T c  ~3 K in Sr x Bi 2 Se 3 arises upon intercalation of Sr into the layered topological insulator Bi 2 Se 3 . Here we elucidate the anisotropy of the normal and superconducting state of Sr 0.1 Bi 2 Se 3 with angular dependent magnetotransport and thermodynamic measurements. High resolution x-ray diffraction studies underline the high crystalline quality of the samples. We demonstrate that the normal state electronic and magnetic properties of Sr 0.1 Bi 2 Se 3 are isotropic in the basal plane while we observe a large two-fold in-plane anisotropy of the upper critical field in the superconducting state. Our results support the recently proposed odd-parity nematic state characterized by a nodal gap of Eu symmetry in Sr x Bi 2 Se 3 .

Optical and thermoelectric properties of nano-particles based Bi2(Te1-xSex)3 thin films

NASA Astrophysics Data System (ADS)

Adam, A. M.; Lilov, E.; Petkov, P.

2017-01-01

Nano-particles of Bi2Te3 and Bi2(Te1-xSex)3 films were deposited using vacuum thermal evaporation technique from previously prepared bulk alloys synthesized by melting method. Optical and thermoelectric properties were studied in the temperature range of 300-473K. The formation of none- and Se-doped Bi2Te3 nano-particles was verified by EDX and XRD analysis. TEM, SEM and AFM analysis showed the prepared films are polycrystalline in nature. The measurements of electrical conductivity and Seebeck coefficient, alongside with thermal conductivity calculations, resulted in the highest values of thermoelectric power at high temperature to be reported. The maximum value of power factor was calculated at 62.82917 μWK-2cm-1 for (Bi2Se0.3Te1.7) sample at 463 K. On the addition of Se to Bi2Te3 film, a significant decrease of the electronic thermal conductivity (Kel) from 2.181 × 10-2 to 0.598 × 10-2 (μW/cm.K) could be achieved. Figure of merit (ZT) calculations showed a maximum value of 0.85 at room temperature, for Bi2Te3. Besides the increase of ZT value for all samples at higher temperature, surprisingly, a value of 2.75 for (Bi2Se1.2Te1.8) was obtained. We believe our results could open avenues for new applications.

Substituent effect on photophysical properties of bi-1,3,4-oxadiazole derivatives in solution

NASA Astrophysics Data System (ADS)

Chen, Fangyi; Tian, Taiji; Zhao, Chengxiao; Bai, Binglian; Li, Min; Wang, Haitao

2016-04-01

A series of phenyl substituted bi-1,3,4-oxadiazole derivatives were designed and synthesized; the effect of substituent on the photophysical properties and molecular electronic structures was fully studied by the combination of experimental techniques and theoretical calculations. Compared to parent compound without any substituent (BOXD), fluoro-substituent shows little effect on the absorption and emission spectra, whilst a little larger spectral red-shift could be observed for methoxy-, nitro-substituted derivatives and thienyl-substituted bi-1,3,4-oxadiazole (TBOXD). These spectral changes can be well explained by theoretically calculated HOMO and LUMO energy level changes. All these molecules show high fluorescence quantum yield except for nitro-substituted derivative in dilute solutions. The quantum yield of BOXD changes with the concentration and exhibits a high value at the concentrated solution. This work revealed the influence of substituent on the photophysical properties of bi-1,3,4-oxadizaole derivatives in dilute solutions and provided guidance for designing molecules with potential application.

Structural, electronic, magnetic and thermodynamic properties of Ni1-xTixO alloys an ab initio calculation and Monte Carlo study

NASA Astrophysics Data System (ADS)

Klaa, K.; Labidi, S.; Masrour, R.; Jabar, A.; Labidi, M.; Amara, A.; Drici, A.; Hlil, E. K.; Ellouze, M.

2018-06-01

Structural, electronic, magnetic and thermodynamic main features for Ni1-xTixO ternary alloys in rock-salt structure with Ti content in the range ? were studied using the full potential Linearized augmented plane wave (FP-LAPW) method within density functional theory. The exchange-correlation potential was calculated by the generalized gradient approximation. The analysis of the electronic density of states curves allowed the computation of the magnetic moments which are considered to lie along (010) axes. The thermodynamic stability of this alloy was investigated by calculating the excess enthalpy of mixing ? as well as the phase diagram. In addition, the Monte Carlo simulations have been exploited to calculate the transition temperature and magnetic coercive field in the alloy.

Phase transition studies of Na3Bi system under uniaxial strain

NASA Astrophysics Data System (ADS)

Nie, Tiaoping; Meng, Lijun; Li, Yanru; Luan, Yanhua; Yu, Jun

2018-03-01

We investigated the electronic properties and phase transitions of Na3Bi in four structural phases (space groups P63/mmc, P \\overline{3} c1, Fm \\overline{3} m and Cmcm) under constant-volume uniaxial strain using the first-principles method. For P63/mmc and P \\overline{3} c1-Na3Bi, an important phase transition from a topological Dirac semimetal (TDS) to a topological insulator appears under compression strain around 4.5%. The insulating gap increases with the increasing compressive strain and up to around 0.1 eV at a strain of 10%. However, both P63/mmc and P \\overline{3} c1-Na3Bi still keep the properties of a TDS within a tensile strain of 0-10%, although the Dirac points move away from the Γ point along Γ-A in reciprocal space as the tensile strain increases. The Na3Bi with space group Fm \\overline{3} m is identified as a topological semimetal with the inverted bands between Na-3s and Bi-6p and a parabolic dispersion in the vicinity of Γ point. Interestingly, for Fm \\overline{3} m-Na3Bi, both compression and tensile strain lead to a TDS which is identified by calculating surface Fermi arcs and topological invariants at time-reversal planes (k z   =  0 and k z   =  π/c) in reciprocal space. Additionally, we confirmed the high pressure phase Cmcm-Na3Bi is an ordinary insulator with a gap of about 0.62 eV. It is noteworthy that its gap almost keeps constant around 0.60 eV within a compression strain of 0-10%. In contrast, a remarkable phase transition from an insulator to a metal phase appears under tensile strain. Moreover, this phase transition is highly sensitive to tensile strain and takes place only at a strain 1.0%. These strain-induced electronic structures and phase transitions of the Na3Bi system in various phases are important due to their possible applications under high pressure in future electronic devices.

Synthesis and characterization of (1-x)Bi(Mg{sub 2/3}Sb{sub 1/3})O{sub 3}-xPbTiO{sub 3} piezoceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Upadhyay, Ashutosh; Dwivedi, Saurabh; Pandey, Rishikesh

2016-05-23

We present here the comprehensive x-ray diffraction and polarization-electric field hysteresis studies on (1-x)Bi(Mg{sub 2/3}Sb{sub 1/3})O{sub 3}-xPbTiO{sub 3} piezoceramics with x = 0.52, 0.56 and 0.60. The powder x-ray diffraction data reveals the presence of tetragonal phase for all the compositions. The saturation of hysteresis loop is observed for x ≤ 0.56.

Phase equilibria investigations and thermodynamic modeling of the system Bi2O3-Al2O3

NASA Astrophysics Data System (ADS)

Oudich, F.; David, N.; Mathieu, S.; Vilasi, M.

2015-02-01

The system Bi2O3-Al2O3 has been experimentally investigated above 600 °C by DTA, XRD and EPMA under air and low oxygen pressure. Only two compounds were found to exist in equilibrium, which are Bi2Al4O9(1Bi2O3:2Al2O3) and Bi25AlO39(25:1). The latter exhibits a sillenite structure and does not contain pentavalent bismuth. A peritectoid decomposition of (25:1) and a peritectic melting of (1:2) occur at 775 °C and 1075 °C respectively, while an eutectic transformation was observed at 815 °C for 97 mol% Bi2O3. On the basis of the results obtained within the present work as well as experimental data provided from literature, a thermodynamic modeling where the liquid phase is described by the two-sublattice ionic liquid model was performed according to the Calphad approach. The resulting thermodynamic optimization yielded good agreement with experimental results in the investigated region.

High-temperature solution growth and characterization of (1-x)PbTiO3-xBi(Zn2/3Nb1/3)O3 piezo-/ferroelectric single crystals

NASA Astrophysics Data System (ADS)

Paterson, Alisa R.; Zhao, Jinyan; Liu, Zenghui; Wu, Xiaoqing; Ren, Wei; Ye, Zuo-Guang

2018-03-01

Complex perovskite PbTiO3-Bi(Me‧Me″)O3 solid solutions represent new materials systems that possess a higher Curie temperature (TC) than the relaxor-PbTiO3 solid solutions, and are useful for potential applications. To this end, novel ferroelectric single crystals of the (1-x)PbTiO3-xBi(Zn2/3Nb1/3)O3 (PT-BZN) solid solution were successfully grown by the high-temperature solution growth (HTSG) method. Powder X-ray diffraction shows that the symmetry of the grown crystals is tetragonal. The dielectric permittivity and optical domain structures were characterized by dielectric measurements and polarized light microscopy, respectively, as a function of temperature, revealing a first-order ferroelectric-paraelectric phase transition at a TC of 436 ± 2 °C. Based on the TC, the average composition of the crystal platelet was estimated to be 0.58PT-0.42BZN. Piezoresponse force microscopy measurements of the phase and amplitude as a function of voltage reveal the complex polar domain structure and demonstrate the ferroelectric switching behaviour of these materials. These results suggest that the PT-BZN single crystals indeed form a new family of high TC piezo-/ferroelectric materials which are potentially useful for the fabrication of electromechanical transducers for high-temperature applications.

Phase Equilibria and Crystal Chemistry in Portions of the System SrO-CaO-Bi2O3-CuO, Part II—The System SrO-Bi2O3-CuO

PubMed Central

Roth, R. S.; Rawn, C. J.; Burton, B. P.; Beech, F.

1990-01-01

New data are presented on the phase equilibria and crystal chemistry of the binary systems Sr0-Bi203 and SrO-CuO and the ternary system SrO-Bi2O3-CuO. Symmetry data and unit cell dimensions based on single crystal and powder x-ray diffraction measurements are reported for all the binary SrO-Bi2O3 phases, including a new phase identified as Sr6Bi2O9. The ternary system contains at least four ternary phases which can be formed in air at ~900 °C. These are identified as Sr2Bi2CuO6, Sr8Bi4Cu5O19+x, Sr3Bi2Cu2O8 and a solid solution (the Raveau phase) which, for equilibrium conditions at ~900 °C, corresponds approximately to the formula Sr1.8−xBi2.2+xCu1±x/2Oz.(0.0⩽x⩽~0.15). Superconductivity in this phase apparently occurs only in compositions that correspond to negative values of x. Compositions that lie outside the equilibrium Raveau-phase field often form nearly homogeneous Raveau-phase products. Typically this occurs after relatively brief heat treatments, or in crystallization of a quenched melt. PMID:28179779

Roles of Cu in the Enhanced Thermoelectric Properties in Bi0.5Sb1.5Te3

PubMed Central

Hao, Feng; Qiu, Pengfei; Song, Qingfeng; Chen, Hongyi; Lu, Ping; Ren, Dudi; Shi, Xun; Chen, Lidong

2017-01-01

Recently, Cu-containing p-type Bi0.5Sb1.5Te3 materials have shown high thermoelectric performances and promising prospects for practical application in low-grade waste heat recovery. However, the position of Cu in Bi0.5Sb1.5Te3 is controversial, and the roles of Cu in the enhancement of thermoelectric performance are still not clear. In this study, via defects analysis and stability test, the possibility of Cu intercalation in p-type Bi0.5Sb1.5Te3 materials has been excluded, and the position of Cu is identified as doping at the Sb sites. Additionally, the effects of Cu dopants on the electrical and thermal transport properties have been systematically investigated. Besides introducing additional holes, Cu dopants can also significantly enhance the carrier mobility by decreasing the Debye screen length and weakening the interaction between carriers and phonons. Meanwhile, the Cu dopants interrupt the periodicity of lattice vibration and bring stronger anharmonicity, leading to extremely low lattice thermal conductivity. Combining the suppression on the intrinsic excitation, a high thermoelectric performance—with a maximum thermoelectric figure of merit of around 1.4 at 430 K—has been achieved in Cu0.005Bi0.5Sb1.495Te3, which is 70% higher than the Bi0.5Sb1.5Te3 matrix. PMID:28772610

La2/3Sr1/3MnO3-La0.1Bi0.9MnO3 heterostructures for spin filtering

NASA Astrophysics Data System (ADS)

Gajek, M.; Bibes, M.; Varela, M.; Fontcuberta, J.; Herranz, G.; Fusil, S.; Bouzehouane, K.; Barthélémy, A.; Fert, A.

2006-04-01

We have grown heterostructures associating half-metallic La2/3Sr1/3MnO3 (LSMO) bottom electrodes and ferromagnetic La0.1Bi0.9MnO3 (LBMO) tunnel barriers. The layers in the heterostructures have good structural properties and top LBMO films (4 nm thick) have a very low roughness when deposited onto LSMO/SrTiO3(1.6 nm) templates. The LBMO films show an insulating behavior and a ferromagnetic character that are both preserved down to very low thicknesses. They are thus suitable for being used as tunnel barriers. Spin-dependent transport measurements performed on tunnel junctions defined from LSMO/SrTiO3/LBMO/Au samples show a magnetoresistance of up to ~90% at low temperature and bias. This evidences a spin-filtering effect by the LBMO layer, with a spin-filtering efficiency of ~35%.

A Raman scattering study of the structural ordering in Bi1- x La x FeO3 ceramic ferroelectromagnetics

NASA Astrophysics Data System (ADS)

Teplyakova, N. A.; Titov, S. V.; Verbenko, I. A.; Sidorov, N. V.; Reznichenko, L. A.

2015-09-01

Based on Raman spectra, we have studied structural ordering processes in ceramics of ferroelectromagnetics Bi1- x La x FeO3 ( x = 0.075-0.20). It has been found that the structure of Bi1- x La x FeO3 is close to the structure of the crystal BiFeO3. However, lines in Raman spectra of Bi1- x La x FeO3 are considerably broadened compared to lines in the Raman spectrum of the BiFeO3 single crystal, which indicates that the structure of solid solutions is much more disordered. In Raman spectra of Bi1- x La x FeO3, in the range of librational vibrations of octahedra as a whole (50-90 cm-1), several groups of lines are observed in frequency ranges 59-69, 72-77, and 86-92 cm-1 (depending on the composition of solid solution). This confirms X-ray data that examined solid solutions are not single-phase. At a La content x = 0.120, Raman lines in the low-frequency spectral range narrow, which indicates that the ordering of structural units in cationic sublattices somewhat increases. Upon an increase in the content of La in the Bi1- x La x FeO3 structure, no unambiguous dependence of parameters of spectral lines is observed. It is likely that this is explained by the fact that, as the value of x increases, the character of the incorporation of La into the structure of the solid solution changes.

The influence of excess K2O on the electrical properties of (K,Na)1/2Bi1/2TiO3 ceramics

NASA Astrophysics Data System (ADS)

Li, Linhao; Li, Ming; Sinclair, Derek C.

2018-04-01

The solid solution (KxNa0.50-x)Bi0.50TiO3 (KNBT) between Na1/2Bi1/2TiO3 and K1/2Bi1/2TiO3 (KBT) has been extensively researched as a candidate lead-free piezoelectric material because of its relatively high Curie temperature and good piezoelectric properties, especially near the morphotropic phase boundary (MPB) at x ˜ 0.10 (20 mol. % KBT). Here, we show that low levels of excess K2O in the starting compositions, i.e., (Ky+0.03Na0.50-y)Bi0.50TiO3.015 (y-series), can significantly change the conduction mechanism and electrical properties compared to a nominally stoichiometric KNBT series (KxNa0.50-x)Bi0.50TiO3 (x-series). Impedance spectroscopy measurements reveal significantly higher bulk conductivity (σb) values for y ≥ 0.10 samples [activation energy (Ea) ≤ 0.95 eV] compared to the corresponding x-series samples which possess bandgap type electronic conduction (Ea ˜ 1.26-1.85 eV). The largest difference in electrical properties occurs close to the MPB composition (20 mol. % KBT) where y = 0.10 ceramics possess σb (at 300 °C) that is 4 orders of magnitude higher than that of x = 0.10 and the oxide-ion transport number in the former is ˜0.70-0.75 compared to <0.05 in the latter (between 600 and 800 °C). The effect of excess K2O can be rationalised on the basis of the (K + Na):Bi ratio in the starting composition prior to ceramic processing. This demonstrates the electrical properties of KNBT to be sensitive to low levels of A-site nonstoichiometry and indicates that excess K2O in KNBT starting compositions to compensate for volatilisation can lead to undesirable high dielectric loss and leakage currents at elevated temperatures.

[Sensitive determination of Bi3+ by spectrofluorimetry based on graphene oxide-methylene blue system].

PubMed

Zhai, Qiu-ge; Guo, Peng; Zhou, Lin; Liu, Yan-ming

2014-08-01

Graphene oxide was prepared by the modified Hummers method and characterized by field emission scanning electron microscopy. The interaction of graphene with methylene blue was studied by UV absorption, the intensity of two main absorption peaks of methylene blue decreased significantly after the fluorescence was quenched, and the energy transfer didn't occur because the overlap of the absorption spectrum of GO and the emission spectrum of MB is too small. Therefore, the fluorescence quenching of MB and GO was static. When adding a certain amount of Bi3+ in the graphene-methylene blue system, Bi3+ replaces the methylene blue from the graphene-methylene blue complexes because Bi3+ has the smaller volume and is more positively charged. The methylene blue therefore dissociates from the GO-MB complexes, resulting in the recovery of fluorescence of the system. Furthermore, the fluorescence of the system increases with the increase in the amount of Bi3+ due to the enhanced amount of MB in the system. A novel spectrofluorimetric method was therefore developed for the sensitive determination of Bi3+. Some parameters including the concentration of methylene blue, the amount of graphene oxide, the amount of nitric acid and the sequence of reagent adding were optimized to obtain higher sensitivity. The fluorescence of the system was detected at an emission wavelength of 667 nm with excitation at 690 nm. Under the optimized conditions, the concentration of Bi3+ showed good linear relationships with the fluorescence intensity in the range of 0.5-100 micromol x L(-1), with correlation coefficients of r = 0.9955. The limits of detection for Bi3+ was 1.0 x 10(-8) mol x L(-1) (S/N=3). The selectivity of the proposed method was evaluated and the results showed that 1000-fold K+, Ca+, Na+, Mg2+, Cu2+; 100-fold Fe3+, Be2+, SiO2- Al3+, Ni2+, Sb3+, NO3-, Cl-, F-, and 20-fold Pb2+, Hg2+, Cd2+ had negligible interference with the determination of Bi3+. The method has advantages of

Pseudogap and proximity effect in the Bi2Te3/Fe1+yTe interfacial superconductor.

PubMed

He, M Q; Shen, J Y; Petrović, A P; He, Q L; Liu, H C; Zheng, Y; Wong, C H; Chen, Q H; Wang, J N; Law, K T; Sou, I K; Lortz, R

2016-09-02

In the interfacial superconductor Bi2Te3/Fe1+yTe, two dimensional superconductivity occurs in direct vicinity to the surface state of a topological insulator. If this state were to become involved in superconductivity, under certain conditions a topological superconducting state could be formed, which is of high interest due to the possibility of creating Majorana fermionic states. We report directional point-contact spectroscopy data on the novel Bi2Te3/Fe1+yTe interfacial superconductor for a Bi2Te3 thickness of 9 quintuple layers, bonded by van der Waals epitaxy to a Fe1+yTe film at an atomically sharp interface. Our data show highly unconventional superconductivity, which appears as complex as in the cuprate high temperature superconductors. A very large superconducting twin-gap structure is replaced by a pseudogap above ~12 K which persists up to 40 K. While the larger gap shows unconventional order parameter symmetry and is attributed to a thin FeTe layer in proximity to the interface, the smaller gap is associated with superconductivity induced via the proximity effect in the topological insulator Bi2Te3.

Pseudogap and proximity effect in the Bi2Te3/Fe1+yTe interfacial superconductor

PubMed Central

He, M. Q.; Shen, J. Y.; Petrović, A. P.; He, Q. L.; Liu, H. C.; Zheng, Y.; Wong, C. H.; Chen, Q. H.; Wang, J. N.; Law, K. T.; Sou, I. K.; Lortz, R.

2016-01-01

In the interfacial superconductor Bi2Te3/Fe1+yTe, two dimensional superconductivity occurs in direct vicinity to the surface state of a topological insulator. If this state were to become involved in superconductivity, under certain conditions a topological superconducting state could be formed, which is of high interest due to the possibility of creating Majorana fermionic states. We report directional point-contact spectroscopy data on the novel Bi2Te3/Fe1+yTe interfacial superconductor for a Bi2Te3 thickness of 9 quintuple layers, bonded by van der Waals epitaxy to a Fe1+yTe film at an atomically sharp interface. Our data show highly unconventional superconductivity, which appears as complex as in the cuprate high temperature superconductors. A very large superconducting twin-gap structure is replaced by a pseudogap above ~12 K which persists up to 40 K. While the larger gap shows unconventional order parameter symmetry and is attributed to a thin FeTe layer in proximity to the interface, the smaller gap is associated with superconductivity induced via the proximity effect in the topological insulator Bi2Te3. PMID:27587000

The crystal structure of the mixed-layer Aurivillius phase Bi 5Ti 1.5W 1.5O 15

NASA Astrophysics Data System (ADS)

Tellier, J.; Boullay, Ph.; Créon, N.; Mercurio, D.

2005-09-01

The crystal structure of the 1+2 mixed-layer Aurivillius phase Bi 5Ti 1.5W 1.5O 15 (SG I2cm n o 46: -cba, Z=4, a=5.4092(3) Å, b=5.3843(3) Å and c=41.529(3) Å) consisting of the ordered intergrowth of one and two octahedra thick perovskite-type blocks separated by [Bi 2O 2] 2+ slabs is reported. Supported by an electron diffraction investigation and, using the Rietveld analysis, it is shown that this compound should be described using a I-centering lattice in agreement with the generalised structural model of the Aurivillius type compounds recently presented by the authors. The structure of this Bi 5Ti 1.5W 1.5O 15 phase is analyzed in comparison with the related simple members (Bi 2WO 6 and Bi 3Ti 1.5W 0.5O 9). The crystal structure of Bi 3Ti 1.5W 0.5O 9 is also reported.

Integrable Equations in Multi-Dimensions (2+1) are Bi-Hamiltonian Systems,

DTIC Science & Technology

1987-02-01

equation [18]. It should be noted that the 80 equation has more similarities [19] with the Kadomtsev - Petviashvili (KP...Cimento, 39B, 1 (1977). [31] P. Caudrey, Discrete and Periodic Spectral Transforms Related to the Kadomtsev - Petviashvili Equation , preprint U.M.I.S.T. (1985). II ’AI D p-I 4, - -- - -- - - -w 4 ...TOM NONLINEAR STUDIES IDTIC I IELEC )// MAR 2 51988 I / \\ / Integrable Equations in Multi- dimensions (2+1) are Bi-Hamiltonian Systems by A.S.

High-Quality (CH3NH3)3Bi2I9 Film-Based Solar Cells: Pushing Efficiency up to 1.64.

PubMed

Zhang, Zheng; Li, Xiaowei; Xia, Xiaohong; Wang, Zhuo; Huang, Zhongbing; Lei, Binglong; Gao, Yun

2017-09-07

Bismuth-based solar cells have exhibited some advantages over lead perovskite solar cells for nontoxicity and superior stability, which are currently two main concerns in the photovoltaic community. As for the perovskite-related compound (CH 3 NH 3 ) 3 Bi 2 I 9 applied for solar cells, the conversion efficiency is severely restricted by the unsatisfactory photoactive film quality. Herein we report a novel two-step approach- high-vacuum BiI 3 deposition and low-vacuum homogeneous transformation of BiI 3 to (CH 3 NH 3 ) 3 Bi 2 I 9 -for highly compact, pinhole-free, large-grained films, which are characterized with absorption coefficient, trap density of states, and charge diffusion length comparable to those of some lead perovskite analogues. Accordingly, the solar cells have realized a record power conversion of efficiency of 1.64% and also a high external quantum efficiency approaching 60%. Our work demonstrates the potential of (CH 3 NH 3 ) 3 Bi 2 I 9 for highly efficient and long-term stable solar cells.

Study of half-metallicity in BiMnxFe1-xO3

NASA Astrophysics Data System (ADS)

Ameer, Shaan; Jindal, Kajal; Tomar, Monika; Jha, Pradip K.; Gupta, Vinay

2018-05-01

Spin polarized calculations are performed to study the structural and electronic properties of Mn doped BiFeO3 (BMFO) using simplified local spin density approximation (LSDA) functional under density functional theory (DFT). The B-site doping concentration of Mn in BMFO considered to be 16.7 % (BiMn0.167Fe0.833O3). Density of states calculations are carried out for both ferromagnetic (FM) and anti-ferromagnetic (AFM) order in BMFO. The results predict that BMFO is a half metal for both FM and AFM BMFO with magnetization of 29.0000 µB/cell and 1.0000 µB/cell respectively. The ground state of BMFO is found to be antiferromagnetic and demonstrates BMFO to be a potential candidate for spintronic applications.

Room temperature ferromagnetism in BiFe1-xMnxO3 thin film induced by spin-structure manipulation

NASA Astrophysics Data System (ADS)

Shigematsu, Kei; Asakura, Takeshi; Yamamoto, Hajime; Shimizu, Keisuke; Katsumata, Marin; Shimizu, Haruki; Sakai, Yuki; Hojo, Hajime; Mibu, Ko; Azuma, Masaki

2018-05-01

The evolution of crystal structure, spin structure, and macroscopic magnetization of manganese-substituted BiFeO3 (BiFe1-xMnxO3), a candidate for multiferroic materials, were investigated on bulk and epitaxial thin-film. Mn substitution for Fe induced collinear antiferromagnetic spin structure around room temperature by destabilizing the cycloidal spin modulation which prohibited the appearance of net magnetization generated by Dzyaloshinskii-Moriya interaction. For the bulk samples, however, no significant signal of ferromagnetism was observed because the direction of the ordered spins was close to parallel to the electric polarization so that spin-canting did not occur. On the contrary, BiFe1-xMnxO3 thin film on SrTiO3 (001) had a collinear spin structure with the spin direction perpendicular to the electric polarization at room temperature, where the appearance of spontaneous magnetization was expected. Indeed, ferromagnetic hysteresis behavior was observed for BiFe0.9Mn0.1O3 thin film.

Enhanced ferroelectric polarization and magnetization in BiFe{sub 1−x}Sc{sub x}O{sub 3} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, C.A.; Pang, H.Z.; Zhang, A.H.

2015-10-15

Highlights: • Single phase Sc doped BFO ceramics were successfully fabricated. • Dielectric constant and magnetization are enhanced in doped BFO system. • Polarization first increases and then decreases in doped BFO system. • M{sub r} of 0.0105 emu/g and P{sub r} of 16.1 μC/cm{sup 2} were revealed simultaneously at x = 0.01. - Abstract: Multiferroic BiFe{sub 1−x}Sc{sub x}O{sub 3} ceramics with x = 0.00–0.10 were synthesized by rapid liquid phase sintering. The influences of Sc doping on the crystalline structures, dielectric, ferroelectric, and magnetic behaviors of BiFeO{sub 3} ceramics were explored. The X-ray diffraction and the Raman spectrometric analysismore » revealed that all the samples are nearly single phase of rhombohedral structure with the incorporation of Sc ions into BiFeO{sub 3}. With increase doping concentration of x, the dielectric constant, dielectric loss, and remnant polarization for the doped BiFeO{sub 3} increase first and then drop down with further rise of x. A saturated ferroelectric polarization can be achieved at a small amount of Sc doping concentration (x < 0.03), with a optimized remnant polarization of 17.6 μC/cm{sup 2} at x = 0.03. Meanwhile, the magnetization is also slightly increased by introducing Sc dopant, with a maximum remnant magnetization of 0.0105 emu/g at x = 0.01. These results indicate that BiFeO{sub 3} ceramics with small amounts of Sc-doping may be promising for applications in magnetoelectric devices.« less

Temperature-independent ferroelectric property and characterization of high-TC 0.2Bi(Mg1/2Ti1/2)O3-0.8PbTiO3 thin films

NASA Astrophysics Data System (ADS)

Zhang, Linxing; Chen, Jun; Zhao, Hanqing; Fan, Longlong; Rong, Yangchun; Deng, Jinxia; Yu, Ranbo; Xing, Xianran

2013-08-01

Ferroelectric property stability against elevated temperature is significant for ferroelectric film applications, such as non-volatile ferroelectric random access memories. The high-TC 0.2Bi(Mg1/2Ti1/2)O3-0.8PbTiO3 thin films show the temperature-independent ferroelectric properties, which were fabricated on Pt(111)/Ti/SiO2/Si substrates via sol-gel method. The present thin films were well crystallized in a phase-pure perovskite structure with a high (100) orientation and uniform texture. A remanent polarization (2Pr) of 77 μC cm-2 and a local effective piezoelectric coefficient d33* of 60 pm/V were observed in the 0.2Bi(Mg1/2Ti1/2)O3-0.8PbTiO3 thin films. It is interesting to observe a behavior of temperature-independent ferroelectric property in the temperature range of room temperature to 125 °C. The remanent polarization, coercive field, and polarization at the maximum field are almost constant in the investigated temperature range. Furthermore, the dielectric loss and fatigue properties of 0.2Bi(Mg1/2Ti1/2)O3-0.8PbTiO3 thin films have been effectively improved by the Mn-doping.

Thin single-crystalline Bi2(Te1-xSex)3 ternary nanosheets synthesized by a solvothermal technique

NASA Astrophysics Data System (ADS)

Guo, Jing; Jian, Jikang; Zhang, Zhihua; Wu, Rong; Li, Jin; Sun, Yanfei

2016-01-01

Bi2(Te1-xSex)3 ternary nanosheets have been successfully synthesized through a facile solvothermal technique using diethylenetriamine as solvent, where x can vary from 0 to 1. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) indicate that the as-synthesized Bi2(Te1-xSex)3 samples are nanosheets with rhombohedral structure, and the thickness of the nanosheets can be as thin as several nanometers. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) reveal that the nanosheets are single crystalline with a rhombohedral structure. Energy disperse spectroscopy (EDS) and XRD analysis by Vegard's law confirm that the ternary Bi2(Te1-xSex)3 nanosheets have been obtained here. The growth of the nanosheets is discussed based on an amine-based molecular template mechanism that has been employed to synthesize some other metal chalcogenides.

Thermoelectric Properties in Fermi Level Tuned Topological Materials (Bi1-xSnx)2Te3

NASA Astrophysics Data System (ADS)

Lin, Chan-Chieh; Shon, Won Hyuk; Rathnam, Lydia; Rhyee, Jong-Soo

2018-03-01

We investigated the thermoelectric properties of Sn-doped (Bi1-xSnx)2Te3 (x = 0, 0.1, 0.3, 0.5, and 0.7%) compounds, which is known as topological insulators. Fermi level tuning by Sn-doping can be justified by the n- to p-type transition with increasing Sn-doping concentration, as confirmed by Seebeck coefficient and Hall coefficient. Near x = 0.3 and 0.5%, the Fermi level resides inside the bulk band gap, resulting in a low Seebeck coefficient and increase of electrical resistivity. The magnetoconductivity with applying magnetic field showed weak antilocalization (WAL) effect for pristine Bi2Te3 while Sn-doped compounds do not follow the WAL behavior of magneto-conductivity, implying that the topological surface Dirac band contribution in magneto-conductivity is suppressed with decreasing the Fermi level by Sn-doping. This research can be applied to the topological composite of p-type/n-type topological materials by Fermi level tuning via Sn-doping in Bi2Te3 compounds.

Role of defects in the carrier-tunable topological-insulator (Bi1 -xSbx )2Te3 thin films

NASA Astrophysics Data System (ADS)

Scipioni, Kane L.; Wang, Zhenyu; Maximenko, Yulia; Katmis, Ferhat; Steiner, Charlie; Madhavan, Vidya

2018-03-01

Alloys of Bi2Te3 and Sb2Te3[(Bi1-xSbx) 2Te3] have played an essential role in the exploration of topological surface states, allowing us to study phenomena that would otherwise be obscured by bulk contributions to conductivity. Despite intensive transport and angle resolved photoemission (ARPES) studies, important questions about this system remain unanswered. For example, previous studies reported the chemical tuning of the Fermi level to the Dirac point by controlling the Sb:Bi composition ratio, but the optimum ratio varies widely across various studies. Moreover, it is unclear how the quasiparticle lifetime is affected by the disorder resulting from Sb/Bi alloying. In this work, we use scanning tunneling microscopy and spectroscopy to study the electronic structure of epitaxially grown (Bi,Sb) 2Te3 thin films at the nanoscale. We study Landau levels (LLs) to determine the effect of disorder on the quasiparticle lifetime as well as the position of the Dirac point with respect to the Fermi energy. A plot of the LL peak widths shows that despite the intrinsic disorder, the quasiparticle lifetime is not significantly degraded. We further determine that the ideal Sb concentration to place the Fermi energy to within a few meV of the Dirac point is x ˜0.7 , but that postannealing temperatures can have a significant effect on the crystallinity and Fermi level position. Specifically, high postgrowth annealing temperature can result in better crystallinity and surface roughness, but also produces a larger Te defect density which adds n -type carriers. Finally, in combination with quasiparticle interference imaging, the dispersion is revealed over a large energy range above the Fermi energy, in a regime inaccessible to ARPES. Interestingly, the surface state dispersion for the x ˜0.7 sample shows great similarity to pristine Bi2Te3 . This work provides microscopic information on the role of disorder and composition in determining carrier concentration, surface state

Magnetic properties of solid solutions between BiCrO3 and BiGaO3 with perovskite structures

NASA Astrophysics Data System (ADS)

Belik, Alexei A.

2015-04-01

Magnetic properties of BiCr1-xGaxO3 perovskite-type solid solutions are reported, and a magnetic phase diagram is established. As-synthesized BiCrO3 and BiCr0.9Ga0.1O3 crystallize in a monoclinic (m) C2/c structure. The Néel temperature (TN) decreases from 111 K in BiCrO3 to 98 K in BiCr0.9Ga0.1O3, and spin-reorientation transition temperature increases from 72 K in BiCrO3 to 83 K in BiCr0.9Ga0.1O3. o-BiCr0.9Ga0.1O3 with a PbZrO3-type orthorhombic structure is obtained by heating m-BiCr0.9Ga0.1O3 up to 573 K in air; it shows similar magnetic properties with those of m-BiCr0.9Ga0.1O3. TN of BiCr0.8Ga0.2O3 is 81 K, and TN of BiCr0.7Ga0.3O3 is 63 K. Samples with x = 0.4, 0.5, 0.6 and 0.7 crystallize in a polar R3c structure. Long-range antiferromagnetic order with weak ferromagnetism is observed below TN = 56 K in BiCr0.6Ga0.4O3, TN = 36 K in BiCr0.5Ga0.5O3 and TN = 18 K in BiCr0.4Ga0.6O3. BiCr0.3Ga0.7O3 shows a paramagnetic behaviour because the Cr concentration is below the percolation threshold of 31%.

Enhanced Photocatalytic Activity in Bi1-x Ba x FeO3 Prepared by a PEG400 Assisted Sol-Gel Method

NASA Astrophysics Data System (ADS)

Zhang, Chenlan; Chen, Jianguo; Jin, Dengren; Cheng, Jinrong

2018-03-01

Ferroelectric Bi1-x Ba x FeO3 nanoparticles for x = 0, 0.01, 0.03, 0.05 and 0.10 were synthesized by a polyethylene glycol 400 (PEG400) assisted sol-gel method. X-ray diffraction reveals that Bi1-x Ba x FeO3 nanoparticles exhibit a distorted rhombohedral structure with the R3c space group, and the diffraction peaks shift upon incorporation of Ba. Transmission electron microscope analysis shows that the particle size of Bi1-x Ba x FeO3 nanoparticles is in the range of 30-60 nm, decreasing with an increase in Ba content. Bi1-x Ba x FeO3 nanoparticles have band gaps in the range of 1.68-2.0 eV, which are capable of responding to visible light irradiation. The rate of the photocatalytic degradation of Bi1-x Ba x FeO3 nanoparticles for x = 0.03 to methyl orange (MO) dye achieves about 81% under visible light irradiation for 3 h, which is higher than that of 66% for pure phase BiFeO3 (BFO). Moreover, the effects of Ba2+ modification on the band gap of BFO crystallites have been investigated and discussed.

Positron lifetime studies of defect structures in Ba(1-x)K(x)BiO3

NASA Astrophysics Data System (ADS)

Obrien, J. C.; Howell, R. H.; Radousky, H. B.; Sterne, P. A.; Hinks, D. G.; Folkerts, T. J.; Shelton, R. N.

1990-12-01

Temperature-dependent positron lifetime experiments have been performed from room temperature to cryogenic temperatures on Ba(1-x)K(x)BiO3, for x = 0.4 and 0.5. From the temperature dependence of the positron lifetime in the normal state, we observe a clear signature of competition between separate defect populations to trap the positron. Theoretical calculations of lifetimes of free or trapped positrons have been performed on Ba(1-x)K(x)BiO3, to help identify these defects. Lifetime measurements separated by long times have been performed and evidence of aging effects in the sample defect populations is seen in these materials.

Superconductivity and strong intrinsic defects in LaPd1-xBi2

NASA Astrophysics Data System (ADS)

Han, Fei; Malliakas, Christos D.; Stoumpos, Constantinos C.; Sturza, Mihai; Claus, Helmut; Chung, Duck Young; Kanatzidis, Mercouri G.

2013-10-01

Two new phases LaPd1-xBi2 and CePd1-xBi2 were obtained by growing single crystals in Bi flux. They adopt the tetragonal ZrCuSi2-type structure and feature Bi-square nets and PbO-type PdBi layers with significant partial Pd occupancy. Bulk superconductivity at 2.1 K and metallic behavior above Tc are observed in LaPd1-xBi2. A small residual resistance ratio (RRR) indicates a strong scattering effect induced by the Pd vacancies, which implies an s-wave pairing symmetry in LaPd1-xBi2. The broadening of the resistivity transition was measured under different magnetic fields demonstrating a high upper critical field of 3 T. Hall effect measurements reveal dominantly electron-like charge carriers and single-band transport behavior in LaPd1-xBi2. The paramagnetic CePd1-xBi2 is nonsuperconducting but shows antiferromagnetic ordering below 6 K.

Layer structured bismuth selenides Bi2Se3 and Bi3Se4 for high energy and flexible all-solid-state micro-supercapacitors.

PubMed

Hao, Chunxue; Wang, Lidan; Wen, Fusheng; Xiang, Jianyong; Li, Lei; Hu, Wentao; Liu, Zhongyuan

2018-01-19

In this work, bismuth selenides (Bi 2 Se 3 and Bi 3 Se 4 ), both of which have a layered rhombohedral crystal structure, have been found to be useful as electrode materials for supercapacitor applications. In a liquid electrolyte system (6M KOH), Bi 2 Se 3 nanoplates exhibit much better performance as an electrode material than Bi 3 Se 4 nanoparticles do, delivering a higher specific capacitance (272.9 F g -1 ) than that of Bi 3 Se 4 (193.6 F g -1 ) at 5 mV s -1 . This result may be attributed to the fact that Bi 2 Se 3 nanoplates possess more active electrochemical surfaces for the reversible surface redox reactions owing to their planar quintuple stacked layers (septuple layers for Bi 3 Se 4 ). To meet the demands of electronic skin, we used a novel flexible annular interdigital structure electrode to support the all-solid-state micro-supercapacitors (AMSCs). The Bi 2 Se 3 AMSC device delivers a much better supercapacitor performance, exhibits a large stack capacitance of 89.5 F cm -3 at 20 mV s -1 (Bi 3 Se 4 : 79.1 F cm -3 ), a high energy density of 17.9 mWh cm -3 and a high power density of 18.9 W cm -3 . The bismuth selenides also exhibit good cycle stability, with 95.5% retention after 1000 c for Bi 2 Se 3 (Bi 3 Se 4 :90.3%). Clearly, Bi 2 Se 3 nanoplates can be promising electrode materials for flexible annular interdigital AMSCs.

Layer structured bismuth selenides Bi2Se3 and Bi3Se4 for high energy and flexible all-solid-state micro-supercapacitors

NASA Astrophysics Data System (ADS)

Hao, Chunxue; Wang, Lidan; Wen, Fusheng; Xiang, Jianyong; Li, Lei; Hu, Wentao; Liu, Zhongyuan

2018-02-01

In this work, bismuth selenides (Bi2Se3 and Bi3Se4), both of which have a layered rhombohedral crystal structure, have been found to be useful as electrode materials for supercapacitor applications. In a liquid electrolyte system (6M KOH), Bi2Se3 nanoplates exhibit much better performance as an electrode material than Bi3Se4 nanoparticles do, delivering a higher specific capacitance (272.9 F g-1) than that of Bi3Se4 (193.6 F g-1) at 5 mV s-1. This result may be attributed to the fact that Bi2Se3 nanoplates possess more active electrochemical surfaces for the reversible surface redox reactions owing to their planar quintuple stacked layers (septuple layers for Bi3Se4). To meet the demands of electronic skin, we used a novel flexible annular interdigital structure electrode to support the all-solid-state micro-supercapacitors (AMSCs). The Bi2Se3 AMSC device delivers a much better supercapacitor performance, exhibits a large stack capacitance of 89.5 F cm-3 at 20 mV s-1 (Bi3Se4: 79.1 F cm-3), a high energy density of 17.9 mWh cm-3 and a high power density of 18.9 W cm-3. The bismuth selenides also exhibit good cycle stability, with 95.5% retention after 1000 c for Bi2Se3 (Bi3Se4:90.3%). Clearly, Bi2Se3 nanoplates can be promising electrode materials for flexible annular interdigital AMSCs.

Prominent metallic surface conduction and the singular magnetic response of topological Dirac fermion in three-dimensional topological insulator Bi1.5Sb0.5Te1.7Se1.3.

PubMed

Dutta, Prithwish; Pariari, Arnab; Mandal, Prabhat

2017-07-07

We report semiconductor to metal-like crossover in the temperature dependence of resistivity (ρ) due to the switching of charge transport from bulk to surface channel in three-dimensional topological insulator Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 . Unlike earlier studies, a much sharper drop in ρ(T) is observed below the crossover temperature due to the dominant surface conduction. Remarkably, the resistivity of the conducting surface channel follows a rarely observable T 2 dependence at low temperature, as predicted theoretically for a two-dimensional Fermi liquid system. The field dependence of magnetization shows a cusp-like paramagnetic peak in the susceptibility (χ) at zero field over the diamagnetic background. The peak is found to be robust against temperature and χ decays linearly with the field from its zero-field value. This unique behavior of the χ is associated with the spin-momentum locked topological surface state in Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 . The reconstruction of the surface state with time is clearly reflected through the reduction of the peak height with the age of the sample.

Structural, Dielectric, and Electrical Properties of Bi1- x Pb x Fe1- x (Zr0.5Ti0.5) x O3

NASA Astrophysics Data System (ADS)

Panda, Niranjan; Pattanayak, Samita; Choudhary, R. N. P.

2015-12-01

Polycrystalline samples of Bi1- x Pb x Fe1- x (Zr0.5Ti0.5) x O3 (BPFZTO) with x = 0.0, 0.2, 0.3, and 0.4 were prepared by high-temperature solid-state reaction. Preliminary structural analysis of calcined powders of the materials by use of x-ray powder diffraction confirmed formation of single-phase systems with the tetragonal structure. Room-temperature scanning electron micrographs of the samples revealed uniform distribution of grains of low porosity and different dimensions on the surface of the samples. The frequency-temperature dependence of dielectric and electric properties was studied by use of dielectric and complex impedance spectroscopy over a wide range of frequency (1 kHz to 1 MHz) at different temperatures (25-500°C). The dielectric constant of BiFeO3 (BFO) was enhanced by substitution with Pb(Zr0.5Ti0.5)O3 (PZT) whereas the dielectric loss of the BPFZTO compounds decreased with increasing PZT content. A significant contribution of both grains and grain boundaries to the electrical response of the materials was observed. The frequency-dependence of the ac conductivity of BPFZTO followed Jonscher's power law. Negative temperature coefficient of resistance behavior was observed for all the BPFZTO samples. Conductivity by thermally excited charge carriers and oxygen vacancies in the materials was believed to be of the Arrhenius-type.

Nature of ferroelectric to paraelectric phase transition in multiferroic 0.8BiFeO3-0.2Pb(Fe1/2Nb1/2)O3 ceramics

NASA Astrophysics Data System (ADS)

Patel, Jay Prakash; Singh, Anar; Pandey, Dhananjai

2010-05-01

We present here the results of high temperature powder x-ray diffraction study on 0.8BiFeO3-0.2Pb(Fe1/2Nb1/2)O3, which is isostructural with the well known multiferroic BiFeO3 (BF). It is shown that the room temperature ferroelectric phase of 0.8BF-0.2PFN in the R3c space group transforms to the paraelectric/paraelastic cubic (Pm3¯m) phase directly without any intermediate "β" phase reported in the literature for pure BF. This transition is of first order type as confirmed by the coexistence of R3c and Pm3¯m phases over a 100 K range and discontinuous change in the unit cell volume.

Study of magnetism in Cr doped (Bi1-xSbx)2Te3

NASA Astrophysics Data System (ADS)

Richardella, Anthony; Kandala, Abhinav; Kempinger, Susan; Samarth, Nitin; Grutter, Alex; Borchers, Julie

2015-03-01

The quantum anomalous Hall (QAH) effect was first observed in Cr doped films of the topological insulator (TI) (Bi1-xSbx)2Te3. This ferromagnetic TI opens a gap at the Dirac point and, when the Fermi energy lies inside this gap, a quantized QAH conductance can be observed. The origin of ferromagnetism in this material is still not well understood with the mechanism typically attributed to either a high van-Vleck susceptibility or a carrier mediated RKKY like interaction. To elucidate this we have studied Cry(Bi1-xSbx)2-yTe3 thin films grown by MBE on SrTiO3 (STO) substrates using polarized neutron reflectivity (PNR) while in-situ backgating the film to change the position of the Fermi energy. The films are also characterized by XRD, AFM, TEM and low temperature transport measurements. PNR measurements provide a direct measure of the depth dependent magnetization of a sample. We use this to study how the magnetization changes as the Fermi energy is moved towards the Dirac point. Funded by DARPA and ARO-MURI.

Substrate-induced dielectric polarization in thin films of lead-free (Sr0.5Bi0.5)2Mn2-xTixO6-δ perovskites grown by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Álvarez-Serrano, I.; Ruiz de Larramendi, I.; López, M. L.; Veiga, M. L.

2017-03-01

Thin films of SrBiMn2-xTixO6-δ have been fabricated by Pulsed Laser Deposition on SrTiO3 [100] and [111] substrates. Their texture, width, homogeneity and morphology are evaluated by means of XRD, SEM, XPS, whereas complex impedance spectroscopy is employed to analyze their electrical response. The thickness values range between 80 and 900 nm depending on the experimental conditions. The epitaxial growing could be interpreted in terms of two contributions of microstructural origin: a matrix part and some polycrystalline surface formations (hemi-spheres). Texture studies suggest a fiber-type orientated morphology coherently with the Scanning Electron Microscopy images. XPS analyses indicate a segregation regarding A-sublattice cations, which features depend on the substrate orientation. This segregation could be connected to the development of nanopolar regions. Impedance data show the electrical polarization in the samples to be enhanced compared to bulk response of corresponding powdered samples. A relaxor behavior which fits a Vogel-Fulcher law is obtained for x = 0.50 whereas an almost frequency-independent relaxor ferroelectric behavior is registered for the thinnest film of x = 0.25 composition grown on SrTiO3 [111] substrate. The influence of compositional and structural aspects in the obtained dielectric response is analyzed.

Raman effect in multiferroic Bi5Fe1+xTi3-xO15 solid solutions: A temperature study

NASA Astrophysics Data System (ADS)

Rodríguez Aranda, Ma. Del Carmen; Rodríguez-Vázquez, Ángel G.; Salazar-Kuri, Ulises; Mendoza, María Eugenia; Navarro-Contreras, Hugo R.

2018-02-01

In this work, a Raman study of powder samples of multiferroic Bi5Fe1+xTi3-xO15 solid solutions and Bi6Fe2Ti3O18 as a function of temperature from 27 °C (room temperature) to 850 °C is presented. The values of x (i.e., the Fe composition) for the solid solutions were 1.0, 1.1, 1.3, and 1.4. The temperature coefficients of eight phonon frequencies were determined for all the samples. The large observed phonon broadenings with increasing temperature precluded the observation of several of the phonon bands above defined temperatures in the range of 200-700 °C depending on the sample. These phonon broadenings were explained on the basis of the Klemens model, which considers that the broadenings are due to the thermal expansion of the lattice with a major contribution in terms of magnitude from anharmonic phonon-phonon interactions. However, some evidence for the presence of several of the phonons persisted up to 800-850 °C. These solid solutions are expected to exhibit a ferroelectric-paraelectric phase transition at 742 to 750 °C and a ferromagnetic-antiferromagnetic transition at 426 °C. We also observed changes in the slopes of the temperature dependence of the phonon frequencies for the lines at 228 cm-1 for Bi5FeTi3O15 and 330 cm-1 for Bi6Fe2Ti3O18 at temperatures of 247 °C and 347 °C, respectively. No similar temperature-frequency slope changes indicative of possible phase transitions were observed for any of the phonon lines of the other three Bi5Fe1+xTi3-xO15 solid solutions examined.

A[Bi(3)Ti(4)O(13)] and A[Bi(3)PbTi(5)O(16)] (A = K, Cs): New n = 4 and n = 5 Members of the Layered Perovskite Series, A[A'(n)()(-)(1)B(n)()O(3)(n)()(+1)], and Their Hydrates.

PubMed

Gopalakrishnan, J.; Sivakumar, T.; Thangadurai, V.; Subbanna, G. N.

1999-06-14

We describe the synthesis and structural characterization of new layered bismuth titanates, A[Bi(3)Ti(4)O(13)] and A[Bi(3)PbTi(5)O(16)] for A = K, Cs, corresponding to n = 4 and 5 members of the Dion-Jacobson series of layered perovskites of the general formula, A[A'(n)()(-)(1)B(n)()O(3)(n)()(+1)]. These materials have been prepared by solid state reaction of the constituents containing excess alkali, which is required to suppress the formation of competitive Aurivillius phases. Unlike the isostructural niobates and niobium titanates of the same series, the new phases reported here are spontaneously hydrated-a feature which could make them potentially useful as photocatalysts for water splitting reaction. On hydration of the potassium compounds, the c axis expands by ca. 2 Å and loses its doubling [for example, the tetragonal lattice parameters of K[Bi(3)Ti(4)O(13)] and its dihydrate are respectively a = 3.900(1) Å, c = 37.57(2) Å; a = 3.885(1) Å, c = 20.82(4) Å]; surprisingly, the cesium analogues do not show a similar change on hydration.

Structural Changes in 2D BiSe Bilayers as n Increases in (BiSe)1+δ(NbSe2)n (n = 1-4) Heterostructures.

PubMed

Mitchson, Gavin; Hadland, Erik; Göhler, Fabian; Wanke, Martina; Esters, Marco; Ditto, Jeffrey; Bigwood, Erik; Ta, Kim; Hennig, Richard G; Seyller, Thomas; Johnson, David C

2016-09-28

(BiSe) 1+δ (NbSe 2 ) n heterostructures with n = 1-4 were synthesized using modulated elemental reactants. The BiSe bilayer structure changed from a rectangular basal plane with n = 1 to a square basal plane for n = 2-4. The BiSe in-plane structure was also influenced by small changes in the structure of the precursor, without significantly changing the out-of-plane diffraction pattern or value of the misfit parameter, δ. Density functional theory calculations on isolated BiSe bilayers showed that its lattice is very flexible, which may explain its readiness to adjust shape and size depending on the environment. Correlated with the changes in the BiSe basal plane structure, analysis of scanning transmission electron microscope images revealed that the occurrence of antiphase boundaries, found throughout the n = 1 compound, is dramatically reduced for the n = 2-4 compounds. X-ray photoelectron spectroscopy measurements showed that the Bi 5d 3/2 , 5d 5/2 doublet peaks narrowed toward higher binding energies as n increased from 1 to 2, also consistent with a reduction in the number of antiphase boundaries. Temperature-dependent electrical resistivity and Hall coefficient measurements of nominally stoichiometric samples in conjunction with structural refinements and XPS data suggest a constant amount of interlayer charge transfer independent of n. Constant interlayer charge transfer is surprising given the changes in the BiSe in-plane structure. The structural flexibility of the BiSe layer may be useful in designing multiple constituent heterostructures as an interlayer between structurally dissimilar constituents.

Fermi-level tuning of the Dirac surface state in (Bi1-x Sb x )2Se3 thin films

NASA Astrophysics Data System (ADS)

Satake, Yosuke; Shiogai, Junichi; Takane, Daichi; Yamada, Keiko; Fujiwara, Kohei; Souma, Seigo; Sato, Takafumi; Takahashi, Takashi; Tsukazaki, Atsushi

2018-02-01

We report on the electronic states and the transport properties of three-dimensional topological insulator (Bi1-x Sb x )2Se3 ternary alloy thin films grown on an isostructural Bi2Se3 buffer layer on InP substrates. By angle-resolved photoemission spectroscopy, we clearly detected Dirac surface states with a large bulk band gap of 0.2-0.3 eV in the (Bi1-x Sb x )2Se3 film with x  =  0.70. In addition, we observed by Hall effect measurements that the dominant charge carrier converts from electron (n-type) to hole (p-type) at around x  =  0.7, indicating that the Fermi level can be controlled across the Dirac point. Indeed, the carrier transport was shown to be governed by Dirac surface state in 0.63  ⩽  x  ⩽  0.75. These features suggest that Fermi-level tunable (Bi1-x Sb x )2Se3-based heterostructures provide a platform for extracting exotic topological phenomena.

[Over-expressed Bax inhibitor 1 (BI-1) inhibits apoptosis of hippocampal neurons via endoplasmic reticulum IRE1-JNK pathway in rats with subarachnoid hemorrhage].

PubMed

Liu, Jiaxin; Zhou, Shuai; Qian, Xiying; Zhang, Yueting; Zhao, Jianhua

2017-10-01

Objective To investigate the protective effect of lentivirus-mediated BI-1 overexpression on hippocampal neurons in rats with subarachnoid hemorrhage (SAH) and the relationship with endoplasmic reticulum IRE1-JNK signaling pathway. Methods The lentivirus solution of BI-1 over-expression was injected into the brain of rats 24 hours before SAH rat model was established by intravascular puncture method. At 24 hours after modeling, the brain water content and neurological score of the rats were measured. The apoptosis of hippocampal neurons was detected by TUNEL assay. Western blotting was used to detect the expressions of BI-1 protein and endoplasmic reticulum stress (ERS) marker proteins GRP78 and IRE1. ERS in hippocampal neurons of the rats with SAH was intervened by IRE1α-specific inhibitor KIRA6, and then the protein expressions of p-IRE1, p-JNK, Bax, Bcl2 and caspase-3 were detected by Western blotting. Results BI-1 over-expression improved neurobehavioral score, decreased brain water content and hippocampal neuron apoptosis rate, and also down-regulated GRP78 and IRE1 protein levels in the rats with SAH. Both the interference of KIRA6 and the over-expression of BI-1 inhibited the expressions of p-IRE1, p-JNK, Bax and caspase-3, and promoted the expression of anti-apoptotic protein Bcl2. Conclusion Over-expression of BI-1 can inhibit the apoptosis of hippocampal neurons in rats with SAH by inhibiting the activation of ERS-mediated IRE1-JNK signaling pathway, thus ultimately attenuating the early brain injury following SAH.

Evolution of structural, electronic and magneto-transport properties of Sr2Ir1-xTixO4 5d based oxide

NASA Astrophysics Data System (ADS)

Bhatti, Imtiaz Noor; Pramanik, A. K.

2018-05-01

To investigate the effect of chemical doping on structural and transport properties in Sr2IrO4, in this study we have doped Ti4+ (3d0) at Ir4+ (5d5) site. Thus Ti doping introduces hole in the electronic band moreover, it also weaken the spin orbital coupling (SOC) and enhance electronic correlation (U). We have prepared the polycrystalline samples of Sr2Ir1-xTixO4 with x = 0.0 0.05 and 0.10 with solid state reaction method. Single phase and chemically pure samples were obtained. All samples crystalizes in tetragonal structure and I41/acd symmetry. The structural analysis shows the evolution of lattice parameter with doping. The temperature dependent resistivity is measured using four probe technique down in the temperature range 5 K-300 K. The resistivity increases with Ti doping. Temperature dependency of resistivity is explained by thermal activated 2-dimensional Mott Variable Hopping range model. To further understand the transport behavior both temperature and field dependent magneto-resistance is also studied. Negative magneto-resistance (MR) has been observed for all samples at 50 K. The MR shows quadratic field dependence at high field, implies a relevance of a quantum interference effect in this spin orbital coupled insulator.

Evolving morphotropic phase boundary in lead-free (Bi1/2Na1/2)TiO3-BaTiO3 piezoceramics

NASA Astrophysics Data System (ADS)

Jo, Wook; Daniels, John E.; Jones, Jacob L.; Tan, Xiaoli; Thomas, Pamela A.; Damjanovic, Dragan; Rödel, Jürgen

2011-01-01

The correlation between structure and electrical properties of lead-free (1-x)(Bi1/2Na1/2)TiO3-xBaTiO3 (BNT-100xBT) polycrystalline piezoceramics was investigated systematically by in situ synchrotron diffraction technique, combined with electrical property characterization. It was found that the morphotropic phase boundary (MPB) between a rhombohedral and a tetragonal phase evolved into a morphotropic phase region with electric field. In the unpoled material, the MPB was positioned at the transition from space group R3m to P4mm (BNT-11BT) with optimized permittivity throughout a broad single-phase R3m composition regime. Upon poling, a range of compositions from BNT-6BT to BNT-11BT became two-phase mixture, and maximum piezoelectric coefficient was observed in BNT-7BT. It was shown that optimized electrical properties are related primarily to the capacity for domain texturing and not to phase coexistence.

Structural, vibrational, and electronic topological transitions of Bi1.5Sb0.5Te1.8Se1.2 under pressure

NASA Astrophysics Data System (ADS)

Kim, Joon-Seok; Juneja, Rinkle; Salke, Nilesh P.; Palosz, Witold; Swaminathan, Venkataraman; Trivedi, Sudhir; Singh, Abhishek K.; Akinwande, Deji; Lin, Jung-Fu

2018-03-01

Topological insulators have been the subject of intense research interest due to their unique surface states that are topologically protected against scattering or defects. However, the relationship between the crystal structure and topological insulator state remains to be clarified. Here, we show the effects of hydrostatic pressure on the structural, vibrational, and topological properties of the topological insulator Bi1.5Sb0.5Te1.8Se1.2 up to 45 GPa using X-ray diffraction and Raman spectroscopy in a diamond anvil cell, together with first-principles theoretical calculations. Two pressure-induced structural phase transitions were observed: from ambient rhombohedral R 3 ¯ m phase to a monoclinic C2/m phase at ˜13 GPa, and to a disordered I4/mmm phase at ˜22 GPa. In addition, the alloy undergoes several electronic transitions within the R 3 ¯ m phase: indirect to direct bulk band gap transition at ˜5.8 GPa, bulk gap closing with an appearance of Dirac semimetal (DSM) state at ˜8.2 GPa, and to a trivial semimetal state at ˜12.1 GPa. Anomalies in c/a ratio and Raman full width at half maximum that coincide with the DSM phase suggest the contribution of electron-phonon coupling to the transition. Compared to binary end members Bi2Te3, Bi2Se3, and Sb2Te3, the structural phase transition and anomaly were observed at higher pressures in Bi1.5Sb0.5Te1.8Se1.2. These results suggest that the topological transitions are precursors to the structural phase transitions.

Stabilized antiferroelectricity in xBiScO3-(1-x)NaNbO3 lead-free ceramics with established double hysteresis loops

NASA Astrophysics Data System (ADS)

Gao, Lisheng; Guo, Hanzheng; Zhang, Shujun; Randall, Clive A.

2018-02-01

We previously reported various solid solution systems that demonstrated the stabilized antiferroelectric (P) phases in NaNbO3 through lowering the tolerance factor. However, all those reported modifications were achieved by adding A2+B4+O3 type solid solutions. A lead-free antiferroelectric (AFE) solid solution xBiScO3-(1-x)NaNbO3 was rationalized by adopting the tolerance factor design rule. Specifically, adding BiScO3 was found to effectively stabilize the AFE phase without changing the crystal symmetry of NaNbO3. Microstructure and electron zone axis diffraction patterns from transmission electron microscopy revealed the stabilized AFE (P) phase in this solid solution. Besides, the electric-field-induced polarization with a double-hysteresis loop was observed. The present results pointed out that the strategy could also be applied while adding A3+B3+O3 type solid solutions. In addition, it expanded the compositional design that can be applied to antiferroelectric materials.

Temperature Dependence of the Tunneling Conductance in Ba_1-xK_xBiO_3

NASA Astrophysics Data System (ADS)

Miyakawa, N.; Ozyuzer, L.; Zasadzinski, J. F.

1997-03-01

Tunneling measurements have been made on high-density polycrystalline pellets of Ba_1-xK_xBiO3 using a point contact method. The temperature dependence (up to 30 K) and magnetic field dependence (up to 6T) of the tunneling conductance has been measured. It is found that at temperatures less than 4.2 K the gap region conductance can be fit with a BCS density of states (dos) and thermal smearing only. However, as the temperature is increased a quasiparticle recombination rate, Γ, which increases as T^n (n ~ 3) must be included in the dos to fit the data. The behavior of Γ (T) does not follow the strong-coupling theory of Kaplan et al. (S.B. Kaplan et al. Phys. Rev. B 14), 4854 (1976) We investigate whether this anomalous power law dependence can come out of Eliashberg theory using the electron-phonon spectral function, a^2F(ω) for Ba_1-xK_xBiO_3.

Bi-phasic regulation of glycogen content in astrocytes via Cav-1/PTEN/PI3K/AKT/GSK-3β pathway by fluoxetine.

PubMed

Bai, Qiufang; Song, Dan; Gu, Li; Verkhratsky, Alexei; Peng, Liang

2017-04-01

Here, we present the data indicating that chronic treatment with fluoxetine regulates Cav-1/PTEN/PI3K/AKT/GSK-3β signalling pathway and glycogen content in primary cultures of astrocytes with bi-phasic concentration dependence. At lower concentrations, fluoxetine downregulates gene expression of Cav-1, decreases membrane content of PTEN, increases activity of PI3K/AKT, and elevates GSK-3β phosphorylation thus suppressing its activity. At higher concentrations, fluoxetine acts in an inverse fashion. As expected, fluoxetine at lower concentrations increased while at higher concentrations decreased glycogen content in astrocytes. Our findings indicate that bi-phasic regulation of glycogen content via Cav-1/PTEN/PI3K/AKT/GSK-3β pathway by fluoxetine may be responsible for both therapeutic and side effects of the drug.

Structure, microstructure and infrared studies of Ba{sub 0.06}(Na{sub 1/2}Bi{sub 1/2}){sub 0.94}TiO{sub 3}-NaNbO{sub 3} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roy, Sumit K., E-mail: sumit.sxc13@gmail.com; Singh, S. N., E-mail: snsphyru@gmail.com; Prasad, K., E-mail: k.prasad65@gmail.com

2016-05-06

Lead-free solid solutions (1-x)Ba{sub 0.06}(Na{sub 1/2}Bi{sub 1/2}){sub 0.94}TiO{sub 3}-xNaNbO{sub 3} (0 ≤ x ≤ 1.0) were prepared by conventional ceramic fabrication technique. X-ray diffraction and Rietveld refinement analyses of these ceramics were carried out using X’Pert HighScore Plus software to determine the crystal symmetry, space group and unit cell dimensions. Rietveld refinement revealed that NaNbO{sub 3} with orthorhombic structure was completely diffused into Ba{sub 0.06}(Na{sub 1/2}Bi{sub 1/2}){sub 0.94}TiO{sub 3} lattice having the rhombohedral-tetragonal symmetry. EDS and SEM studies were carried out in order to evaluate the quality and purity of the compounds. SEM images showed a change in grain shapemore » with the increase of NaNbO{sub 3} content. FTIR spectra confirmed the formation of solid solution.« less

Microstrain engineered magnetic properties in Bi1-x Ca x Fe1-y Ti y O3-δ nanoparticles: deviation from Néel’s 1/d size-dependent magnetization behaviour

NASA Astrophysics Data System (ADS)

Mocherla, Pavana S. V.; Sahana, M. B.; Gopalan, R.; Ramachandra Rao, M. S.; Nanda, B. R. K.; Sudakar, C.

2017-10-01

Magnetization of antiferromagnetic nanoparticles is known to generally scale up inversely to their diameter (d) according to Néel’s model. Here we report a deviation from this conventional linear 1/d dependence, altered significantly by the microstrain, in Ca and Ti substituted BiFeO3 nanoparticles. Magnetic properties of microstrain-controlled Bi1-x Ca x Fe1-y Ti y O3-δ (y  =  0 and x  =  y) nanoparticles are analyzed as a function of their size ranging from 18 nm to 200 nm. A complex interdependence of doping concentration (x or y), annealing temperature (T), microstrain (ɛ) and particle size (d) is established. X-ray diffraction studies reveal a linear variation of microstrain with inverse particle size, 1/d nm-1 (i.e. ɛ · d  =  16.5 nm·%). A rapid increase in the saturation magnetization below a critical size d c ~ 35 nm, exhibiting a (1/d) α (α  ≈  2.6) dependence, is attributed to the influence of microstrain. We propose an empirical formula M \\propto (1/d)ɛ β (β  ≈  1.6) to highlight the contributions from both the size and microstrain towards the total magnetization in the doped systems. The magnetization observed in nanoparticles is thus, a result of the competing magnetic contribution from the terminated spin cycloid on the surface and counteracting microstrain present at a given size.

Influence of Sn on the thermoelectric properties of (Bi{sub x}Sb{sub 1-x}){sub 2}Te{sub 3} single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kulbachinskii, V.A., E-mail: kulb@mig.phys.msu.ru; Kytin, V.G.; Kudryashov, A.A.

2012-09-15

The influence of tin on the thermoelectric properties of p-(Bi{sub x}Sb{sub 1-x}){sub 2}Te{sub 3} single crystals (x=0; 0.25; 0.5) has been investigated. The temperature dependence of the Seebeck coefficient S, the electrical conductivity {sigma}, the heat conductivity k and the thermoelectric figure of merit of p-(Bi{sub x}Sb{sub 1-x}){sub 2}Te{sub 3} single crystals were measured in the temperature range 7-300 K. By an increase the Sn content, the hole concentration increases in p-(Bi{sub x}Sb{sub 1-x}){sub 2-y}Sn{sub y}Te{sub 3}. The heat conductivity k of the p-(Bi{sub x}Sb{sub 1-x}){sub 2-y}Sn{sub y}Te{sub 3} crystals decreases due to the Sn doping, while the electrical conductivitymore » {sigma} increases in the temperature interval about 200« less

Pressure-induced reinforcement of interfacial superconductivity in a Bi2Te3/Fe1+yTe heterostructure

NASA Astrophysics Data System (ADS)

Shen, Junying; Heuckeroth, Claire; Deng, Yuhang; He, Qinglin; Liu, Hong Chao; Liang, Jing; Wang, Jiannong; Sou, Iam Keong; Schilling, James S.; Lortz, Rolf

2017-12-01

We investigate the hydrostatic pressure dependence of interfacial superconductivity occurring at the atomically sharp interface between two non-superconducting materials: the topological insulator (TI) Bi2Te3 and the parent compound Fe1+yTe of the chalcogenide iron-based superconductors. Under pressure, a significant increase in the superconducting transition temperature Tc is observed. We interpret our data in the context of a pressure-induced enhanced coupling of the Fe1+yTe interfacial layer with the Bi2Te3 surface state, which modifies the electronic properties of the interface layer in a way that superconductivity emerges and becomes further enhanced under pressure. This demonstrates the important role of the TI in the interfacial superconducting mechanism.

Liquidus Projections of Bi-Se-Ga and Bi-Se-Te Ternary Systems

NASA Astrophysics Data System (ADS)

Lin, Po-han; Chen, Sinn-wen; Hwang, Jenn-dong; Chu, Hsu-shen

2016-12-01

This study determines the liquidus projections of both Bi-Se-Ga and Bi-Se-Te ternary systems which are constituent ternary systems of promising Bi-Se-Te-Ga thermoelectric materials. Ternary Bi-Se-Ga and Bi-Se-Te alloys are prepared. Their primary solidification phases are experimentally determined, and thermal analysis experiments are carried out. The liquidus projections are determined based on the ternary experimental results and phase diagrams of constituent binary systems. The Bi-Se-Ga system includes seven primary solidification phases, Bi, Ga, GaSe, Ga2Se3, Se, Bi2Se3, and (Bi2)n(Bi2Se3)m. In the Bi-Se-Te system, there are five primary solidification phases, Bi, (Bi2)n(Bi2Te3)m, Bi2(Se,Te)3, (Se,Te), and (Bi2)n(Bi2Se3)m. Both the (Bi2)n(Bi2Te3)m and (Bi2)n(Bi2Se3)m phases are not a single phase, but a collection of series undetermined phases. Large miscibility gaps are observed in the Bi-Se-Ga system. The temperatures of the invariant reactions, Liquid + Bi + GaSe = Ga and Liquid + Ga2Se3 = Bi + GaSe, are at 495 K (222 °C) and 533 K (260 °C), respectively.

Piezoelectric properties of nonstoichiometric Sr1-xBi2+2x/3Ta2O9 ceramics

NASA Astrophysics Data System (ADS)

Jain, Rajni; Chauhan, Arun Kumar Singh; Gupta, Vinay; Sreenivas, K.

2005-06-01

The effect of poling on the structural, dielectric, and piezoelectric properties has been investigated for sol-gel-derived strontium bismuth tantalate (SBT) [Sr1-xBi2+2x/3Ta2O9] ceramics with x =0.0,0.15,0.30,0.45. The dielectric and ferroelectric properties are found to improve with increase in x up to 0.3. Beyond x >0.3 the properties are found to degrade due to the limited solid solubility and the presence of a mixed phase of bismuth tantalate (BiTaO4) is detected with x =0.45. Poling treatment reduces the dielectric dispersion and dielectric loss in the frequency range (0.1-100kHz). The resonance and antiresonance frequencies increase with increase in x (x=0-0.30), and the corresponding minimum impedance decreases. The measured coupling coefficients (kp) are small (0.0967-0.1) for x =0-0.30, and the electromechanical quality factor (Qm=915) is a maximum for the Sr0.7Bi2.2Ta2O9 composition (x=0.30). The estimated piezoelectric charge coefficient (d31) and piezoelectric voltage coefficient (g31) are 5.2pC/N and 5.8×10-3Vm/N, respectively. The positive values of d31 and g31 and the low dielectric permittivity of SBT yield a high value for the hydrostatic coefficients, despite the low charge coefficient of d33=24pC/N. The maximum values of charge coefficient (dh=34pC/N) and voltage coefficient (gh=39×10-3Vm/N) are obtained for Sr0.7Bi2.2Ta2O9 composition, and the estimated hydrostatic figure of merit (dhgh×10-15=1215m2/N) is high.

Surface Collective Modes in the Topological Insulators Bi 2 Se 3 and Bi 0.5 Sb 1.5 Te 3 - x Se x

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kogar, A.; Vig, S.; Thaler, A.

We used low-energy, momentum-resolved inelastic electron scattering to study surface collective modes of the three-dimensional topological insulators Bi 2 Se 3 and Bi 0.5 Sb 1.5 Te 3 - x Se x . Our goal was to identify the “spin plasmon” predicted by Raghu and co-workers [Phys. Rev. Lett. 104, 116401 (2010)]. Instead, we found that the primary collective mode is a surface plasmon arising from the bulk, free carriers in these materials. This excitation dominates the spectral weight in the bosonic function of the surface χ '' ( q , ω ) at THz energy scales, and is themore » most likely origin of a quasiparticle dispersion kink observed in previous photoemission experiments. Our study suggests that the spin plasmon may mix with this other surface mode, calling for a more nuanced understanding of optical experiments in which the spin plasmon is reported to play a role« less

Surface collective modes in the topological insulators Bi 2Se 3 and Bi 0.5Sb 1.5Te 3-xSe x

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kogar, A.; Gu, G.; Vig, S.

In this study, we used low-energy, momentum-resolved inelastic electron scattering to study surface collective modes of the three-dimensional topological insulators Bi 2Se 3 and Bi 0.5Sb 1.5Te 3-xSe x. Our goal was to identify the “spin plasmon” predicted by Raghu and co-workers [Phys. Rev. Lett. 104, 116401 (2010)]. Instead, we found that the primary collective mode is a surface plasmon arising from the bulk, free carriers in these materials. This excitation dominates the spectral weight in the bosonic function of the surface χ''(q,ω) at THz energy scales, and is the most likely origin of a quasiparticle dispersion kink observed inmore » previous photoemission experiments. Our study suggests that the spin plasmon may mix with this other surface mode, calling for a more nuanced understanding of optical experiments in which the spin plasmon is reported to play a role.« less

Surface Collective Modes in the Topological Insulators Bi 2 Se 3 and Bi 0.5 Sb 1.5 Te 3 - x Se x

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kogar, A.; Vig, S.; Thaler, A.

We used low-energy, momentum-resolved inelastic electron scattering to study surface collective modes of the three-dimensional topological insulators Bi 2Se 3 and Bi 0.5Sb 1.5Te 3-xSe x . Our goal was to identify the “spin plasmon” predicted by Raghu and co-workers [Phys. Rev. Lett. 104, 116401 (2010)]. Instead, we found that the primary collective mode is a surface plasmon arising from the bulk, free carriers in these materials. This excitation dominates the spectral weight in the bosonic function of the surface χ '' ( q , ω ) at THz energy scales, and is the most likely origin of a quasiparticlemore » dispersion kink observed in previous photoemission experiments. Our study suggests that the spin plasmon may mix with this other surface mode, calling for a more nuanced understanding of optical experiments in which the spin plasmon is reported to play a role.« less

Surface collective modes in the topological insulators Bi 2Se 3 and Bi 0.5Sb 1.5Te 3-xSe x

DOE PAGES

Kogar, A.; Gu, G.; Vig, S.; ...

2015-12-15

In this study, we used low-energy, momentum-resolved inelastic electron scattering to study surface collective modes of the three-dimensional topological insulators Bi 2Se 3 and Bi 0.5Sb 1.5Te 3-xSe x. Our goal was to identify the “spin plasmon” predicted by Raghu and co-workers [Phys. Rev. Lett. 104, 116401 (2010)]. Instead, we found that the primary collective mode is a surface plasmon arising from the bulk, free carriers in these materials. This excitation dominates the spectral weight in the bosonic function of the surface χ''(q,ω) at THz energy scales, and is the most likely origin of a quasiparticle dispersion kink observed inmore » previous photoemission experiments. Our study suggests that the spin plasmon may mix with this other surface mode, calling for a more nuanced understanding of optical experiments in which the spin plasmon is reported to play a role.« less

Structural, dielectric and impedance characteristics of lanthanum-modified BiFeO3-PbTiO3 electronic system

NASA Astrophysics Data System (ADS)

Pradhan, S. K.; Das, S. N.; Bhuyan, S.; Behera, C.; Padhee, R.; Choudhary, R. N. P.

2016-06-01

A lanthanum-modified BiFeO3-PbTiO3 binary electronic system has been fabricated by a high-temperature solid-state reaction technique. The structural, dielectric and electrical properties of a single phase of multicomponent system are investigated to understand its ferroelectrics as well as relaxation behavior. The X-ray diffraction structural analysis substantiates the formation of a new stable phase of tetragonal system (with a large c/a ratio 1.23) without any trace of impurity phase. The electrical behavior of the processed material is characterized through impedance spectroscopy in a wide frequency range (1 kHz-1 MHz) over a temperature range of 25-500 °C. It is observed that the substitution of lanthanum-modified PbTiO3 (PT) into BiFeO3 (BFO) reveals enviable multiferroic property which is evident from the ME coefficient measurement and ferroelectric loop. It also reduces the electrical leakage current or tangent loss. The ac conductivity of the solid solution increases with increase in frequency in the low-temperature region. The impedance spectroscopy of the synthesized material reflects the dielectric relaxation of non-Debye type.

The Bi{sub 2}O{sub 3}–Fe{sub 2}O{sub 3}–Sb{sub 2}O{sub 5} system phase diagram refinement, Bi{sub 3}FeSb{sub 2}O{sub 11} structure peculiarities and magnetic properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Egorysheva, A.V., E-mail: anna_egorysheva@rambler.ru; Ellert, O.G.; Gajtko, O.M.

2015-05-15

The refinement of the Bi{sub 2}O{sub 3}–Fe{sub 2}O{sub 3}–Sb{sub 2}O{sub 5} system phase diagram has been performed and the existence of the two ternary compounds has been confirmed. The first one with a pyrochlore-type structure (sp. gr. Fd 3-barm) exists in the wide solid solution region, (Bi{sub 2−x}Fe{sub x})Fe{sub 1+y}Sb{sub 1−y}O{sub 7±δ}, where x=0.1–0.4 and y=−0.13–0.11. The second one, Bi{sub 3}FeSb{sub 2}O{sub 11}, corresponds to the cubic KSbO{sub 3}-type structure (sp. gr. Pn 3-bar) with unit cell parameter a=9.51521(2) Å. The Rietveld structure refinement showed that this compound is characterized by disordered structure. The Bi{sub 3}FeSb{sub 2}O{sub 11} factor groupmore » analysis has been carried out and a Raman spectrum has been investigated. According to magnetization measurements performed at the temperature range 2–300 K it may be concluded that the Bi{sub 3}FeSb{sub 2}O{sub 11} magnetic properties can be substantially described as a superposition of strong short-range antiferromagnetic exchange interactions realizing inside the [(FeSb{sub 2})O{sub 9}] 3D-framework via different pathways. - Graphical abstract: The refinement of the Bi{sub 2}O{sub 3}–Fe{sub 2}O{sub 3}–Sb{sub 2}O{sub 5} system phase diagram has been performed and the existence of the solid solution with a pyrochlore-type structure (sp. gr. Fd 3-barm) and Bi{sub 3}FeSb{sub 2}O{sub 11}, correspond of the cubic KSbO{sub 3}-type structure (sp. gr. Pn 3-bar has been confirmed. The structure refinement, Raman spectroscopy as well as magnetic measurements data of Bi{sub 3}FeSb{sub 2}O{sub 11} are presented. - Highlights: • The Bi{sub 2}O{sub 3}–Fe{sub 2}O{sub 3}–Sb{sub 2}O{sub 5} system phase diagram refinement has been performed. • The Bi{sub 3}FeSb{sub 2}O{sub 11} existence along with pyrochlore structure compound is shown. • It was determined that the Bi{sub 3}FeSb{sub 2}O{sub 11} is of disordered cubic KSbO{sub 3}-type structure. • Factor group

Characterization of magnetic and dielectric properties of Bi(1-x)Gd(x)FeO3 nanoparticles by local structure analyses.

PubMed

Yanoh, Takuya; Kurokawa, Akinobu; Takeuchi, Hiromasa; Yano, Shinya; Onuma, Kazuki; Kondo, Takaya; Miike, Kazunari; Miyasaka, Toshiki; Mibu, Ko; Ichiyanagi, Yuko

2014-03-01

Bi(1-x)Gd(x)FeO3 (0 < or = x < or = 1.0) nanoparticles were synthesized by a wet chemical method. The annealing temperatures were controlled to obtain single-phase Bi(1-x)Gd(x)FeO3 nanoparticles. The crystal diameters decreased as the number of doped Gd ions increased. The crystal structure changed, as the number of Gd ions increased, from rhombohedral to orthorhombic perovskite, at x = 0.2. The behavior of the magnetization curves observed at various values of x (x = 0.05, 0.1, 0.15) of the rhombohedral structure suggested that the canted antiferromagnetism and remanent magnetization (M(r)) drastically increased, compared with those at x = 0 (BiFeO3). It is suggested that the spin-canting angle of the Fe ions increased with the increase in the number of Gd ions. The dielectric properties at x = 0.1 showed that the dielectric loss (tan delta) was improved, compared with that at x = 0 (BiFeO3), by approximately 90%, while the real part of the dielectric constant epsilon' was reduced by approximately 15%. The reason is that the doping impurities restrained the reduction in the leakage current. It was found, from the X-ray absorption fine structure (XAFS) spectra, that Gd ions were doped accurately and that the symmetry of the B site was improved. The Mössbauer analysis suggested the existence of magnetic cycloid spiral ordering.

Doping effect on ferromagnetism, ferroelectricity and dielectric constant in sol-gel derived Bi1-xNdxFe1-yCoyO3 nanoceramics

NASA Astrophysics Data System (ADS)

Das, Sananda; Sahoo, R. C.; Bera, K. P.; Nath, T. K.

2018-04-01

Doping at the post-transition metal site by trivalent rare-earth ions and 3d transition metal site by transition metal ions in perovskite lattice has observed a variety of magnetic and electronic orders with spatially correlated charge, spin and orbital degrees of freedom. Here, we report large ferromagnetism and enhanced dielectric constant (at ∼100 Hz) in chemically synthesized single phase multiferroic Bi1-xNdxFe1-yCoyO3 (x = 0, 0.10; y = 0, 0.10) nanoparticles (average particles size ∼45 nm). We have also examined the ferroelectric nature of our chemically synthesized samples. The Rietveld refinement of the XRD data reveals the structural symmetry breaking from distorted rhombohedral R3c structure of BiFeO3 to the triclinic P1 structure in Bi0.9Nd0.1Fe0.9Co0.1O3 (BNFCO) without having any iron rich impurity phase. The magnetization in these nanoceramics most likely originates from the coexistence of mixed valence states of Fe ion (Fe2+ and Fe3+). A high room temperature dielectric constant (∼1050) has been observed at 100 Hz of BNFCO sample. The frequency dependent anomalies near Neel temperature of antiferromagnet in temperature variation of dielectric study have been observed for all the doped and co-doped samples exhibiting typical characteristic of relaxor ferroelectrics. A spectacular enhancement of remanent magnetization MR (∼7.2 emu/gm) and noticeably large coercivity HC (∼17.4 kOe) at 5 K have been observed in this BNFCO sample. Such emergence of ferromagnetic ordering indicates the canting of the surface spins at the surface boundaries because of the reduction of particle size in nanodimension. We have also observed P-E hysteresis loops with a remanent polarization of 26 μC/cm2 and coercive field of 5.6 kV/cm of this sample at room temperature. From impedance spectroscopy study the estimated activation energy of 0.41 eV suggests the semiconducting nature of our nanoceramic BNCFO sample.

Preparation and visible light photocatalytic activity of Bi2O3/Bi2WO6 heterojunction photocatalysts

NASA Astrophysics Data System (ADS)

Yan, C. Y.; Yi, W. T.; Xiong, J.; Ma, J.

2018-03-01

The Bi2O3 nanorods, flower-like Bi2WO6 and Bi2O3/Bi2WO6 heterojunction composites with the molar ratio of nBi:nW from 2:1, 2.5:1, to 3:1 have been synthesized via one-step hydrothermal method and two-step hydrothermal method, respectively. The products are characterized by powder X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (UV-vis DRS), and scanning electron microscopy (SEM). Photocatalytic experiments indicate that such Bi2O3/Bi2WO6 composite possesses higher photocatalytic activity for RhB degradation under visible-light irradiation in comparison with pure Bi2O3 and Bi2WO6. The enhancement of the photocatalytic activity of the Bi2O3/Bi2WO6 heterojunction catalysts can be ascribed to the reduced recombination of the photoexcited electrons and holes during the photocatalytic reaction. The effect of the molar ratio of nBi:nW on the catalytic performance of the heterojunction catalysts was also investigated. And the optimal molar ratio of nBi:nW is 2.5:1 which was synthesized by one-step hydrothermal method.

Comparative study of A-site order in the lead-free bismuth titanates M{sub 1/2}Bi{sub 1/2}TiO{sub 3} (M=Li, Na, K, Rb, Cs, Ag, Tl) from first-principles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gröting, Melanie, E-mail: groeting@mm.tu-darmstadt.de; Albe, Karsten, E-mail: albe@mm.tu-darmstadt.de

2014-05-01

We investigate the possibility of enhancing chemical order in the relaxor ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3} upon substitution of Na{sup +} by other monovalent cations M{sup +} using total energy calculations based on density functional theory. All chemically available monovalent cations M{sup +}, which are Li, Na, Ag, K, Tl, Rb and Cs, are considered and an analysis of the structurally relaxed structures in terms of symmetry-adapted distortion modes is given in order to quantify the chemically induced structural distortions. We demonstrate that the replacement of Na{sup +} by other monovalent cations can hardly alter the tendency of chemical ordermore » with respect to Na{sub 1/2}Bi{sub 1/2}TiO{sub 3}. Only Tl{sub 1/2}Bi{sub 1/2}TiO{sub 3} and Ag{sub 1/2}Bi{sub 1/2}TiO{sub 3} show enhanced tendency for chemical ordering. Both heavy metals behave similar to the light alkali metals in terms of structural relaxations and relative stabilities of the ordered configurations. Although a comparison of the Goldschmidt factors of components (M TiO{sub 3}){sup −} reveals for Tl a value above the upper stability limit for perovskites, the additional lone-pair effect of Tl{sup +} stabilizes the ordered structure. - Graphical abstract: Amplitudes of chemically induced distortion modes in different ordered perovskites M{sub 1/2}Bi{sub 1/2}TiO{sub 3} and visualisation of atomic displacements associated with distortion mode X{sup +}{sub 1} in the 001-ordered compounds Li{sub 1/2}Bi{sub 1/2}TiO{sub 3} and Cs{sub 1/2}Bi{sub 1/2}TiO{sub 3}. Due to a substantial size mismatch between bismuth (green) and caesium (dark blue), incorporation of the latter leads to enhanced displacements of oxygen atoms (red) and suppresses displacements of titanium (silver) as compared to lithium (light blue) or other smaller monovalent cations. - Highlights: • Lead-free A-site mixed bismuth titanates M{sub 1/2}Bi{sub 1/2}TiO{sub 3} are studied by first-principles calculations. �

Reconciling Local Structure Disorder and the Relaxor State in (Bi1/2Na1/2)TiO3-BaTiO3

NASA Astrophysics Data System (ADS)

Groszewicz, Pedro B.; Gröting, Melanie; Breitzke, Hergen; Jo, Wook; Albe, Karsten; Buntkowsky, Gerd; Rödel, Jürgen

2016-08-01

Lead-based relaxor ferroelectrics are key functional materials indispensable for the production of multilayer ceramic capacitors and piezoelectric transducers. Currently there are strong efforts to develop novel environmentally benign lead-free relaxor materials. The structural origins of the relaxor state and the role of composition modifications in these lead-free materials are still not well understood. In the present contribution, the solid-solution (100-x)(Bi1/2Na1/2)TiO3-xBaTiO3 (BNT-xBT), a prototypic lead-free relaxor is studied by the combination of solid-state nuclear magnetic resonance (NMR) spectroscopy, dielectric measurements and ab-initio density functional theory (DFT). For the first time it is shown that the peculiar composition dependence of the EFG distribution width (ΔQISwidth) correlates strongly to the dispersion in dielectric permittivity, a fingerprint of the relaxor state. Significant disorder is found in the local structure of BNT-xBT, as indicated by the analysis of the electric field gradient (EFG) in 23Na 3QMAS NMR spectra. Aided by DFT calculations, this disorder is attributed to a continuous unimodal distribution of octahedral tilting. These results contrast strongly to the previously proposed coexistence of two octahedral tilt systems in BNT-xBT. Based on these results, we propose that considerable octahedral tilt disorder may be a general feature of these oxides and essential for their relaxor properties.

Preparation and Thermoelectric Properties of Graphite/Bi0.5Sb1.5Te3 Composites

NASA Astrophysics Data System (ADS)

Hu, Wenhua; Zhou, Hongyu; Mu, Xin; He, Danqi; Ji, Pengxia; Hou, Weikang; Wei, Ping; Zhu, Wanting; Nie, Xiaolei; Zhao, Wenyu

2018-06-01

Bismuth telluride zone-melting alloys are the most commercially used thermoelectric materials. However, the zone-melting ingots have weak machinability due to the strong preferred orientation. Here, non-textured graphite/Bi0.5Sb1.5Te3 (G/BST) composites were prepared by a powder metallurgy method combined with cold-pressing and annealing treatments. The composition, microstructure, and thermoelectric properties of the G/BST composites with different mass percentages of G were investigated. It was found that G addition could effectively reduce the thermal conductivity and slightly improve the electrical properties of the BST, which resulted in a large enhancement in the figure-of-merit, ZT. The largest ZT for the xG/BST composites with x = 0.05% reached 1.05 at 320 K, which is increased by 35% as compared with that of the G-free BST materials. This work provided an effective method for preparing non-textured Bi2Te3-based TE materials with a simple process, low cost, and large potential in scale production.

Favorable Concurrence of Static and Dynamic Phenomena at the Morphotropic Phase Boundary of x BiNi0.5Zr0.5O3-(1 -x )PbTiO3

NASA Astrophysics Data System (ADS)

Datta, K.; Neder, R. B.; Chen, J.; Neuefeind, J. C.; Mihailova, B.

2017-11-01

We reveal that concurrent events of inherent entropy boosting and increased synchronization between A - and B -site cation vibrations of an A B O3 -type perovskite structure give rise to a larger piezoelectric response in a ferroelectric system at its morphotropic phase boundary (MPB). It is further evident that the superior piezoelectric properties of x BiNi0.5Zr0.5O3-(1 -x )PbTiO3 in comparison to x BiNi0.5Ti0.5O3-(1 -x )PbTiO3 are due to the absolute flattening of the local potentials for all ferroelectrically active cations with a higher spontaneous polarization at the MPB. These distinctive features are discovered from the analyses of neutron pair distribution functions and Raman scattering data at ambient conditions, which are particularly sensitive to mesoscopic-scale structural correlations. Altogether this uncovers more fundamental structure-property connections for ferroelectric systems exhibiting a MPB, and thereby has a critical impact in contriving efficient novel materials.

Synthesis and microwave dielectric behavior of (Bi1-xPbx)NbO4 ceramics

NASA Astrophysics Data System (ADS)

Butee, S. P.; Kambale, K. R.; Upadhyay, Shaishav; Bashaiah, S.; Raju, K. C. James; Panda, Himanshu

2016-03-01

Ceramic samples of (Bi1-xPbx)NbO4 (x=0, 0.025, 0.05, 0.10, 0.15, 0.20) with 0.75wt.% V2O5 addition sintered at 920∘C, 940∘C and 960∘C are investigated. Pb is selected as a substitute for Bi3+ in BiNbO4 ceramics as it exists in two stable valence states of +2 and +4 and the average valency matches to that of Bi3+. The average Shannon radius (for octahedral coordination) of Pb2+ (1.19Å) and Pb4+(0.775Å) cations is 0.9825Å, which is similar to that of Bi3+ ion (1.03Å). The dense (>94%) polycrystalline (Bi1-xPbx)NbO4 samples fabricated mostly reveal orthorhombic (Pnna) phase (α-BiNbO4, Sp. Gp. 52) by powder XRD. Presence of satellite Pb2Nb2O7 phase, the amount of which is increasing with increase in Pb content, is also noticed. The microwave dielectric constant (ɛr‧) values of the niobates are found to increase from 42 to 71, whereas the quality factor (Qu.f) values are found to decrease from 5400 to 550 GHz with increasing substitution of Pb. The compositions so synthesized are important as hardly there are any microwave dielectric ceramics available with 45<ɛr‧<75.

Synthesis, structural and electron paramagnetic resonance studies on Pb0.9Bi0.1Fe0.7W0.3O3 ceramic

NASA Astrophysics Data System (ADS)

Shivaraja, I.; Matteppanvar, Shidaling; Dadami, Sunanda T.; Rayaprol, Sudhindra; Angadi, Basavaraj

2018-04-01

A single phase Pb0.9Bi0.1Fe0.7W0.3O3 (0.9Pb(Fe2/3W1/3)O3 - 0.1BiFeO3 or PBFW) polycrystalline ceramic was synthesized by the two step solid state reaction method, with low-temperature sintering at 800°C for 30 mins and slow cooling to room temperature (RT). Detailed studies of RT X-ray diffraction (XRD) and Raman spectroscopy measurements confirm the formation of high symmetry cubic structure with Pm-3m space group. The Rietveld refinement was carried out on RT XRD data and the obtained structural parameters are a = b = c = 3.97563(6) Å and unit cell volume = 62.837 (2) Å3. Scanning Electron Microscopy (SEM) images show the uniform distribution of grains with some agglomerated nature. RT Raman spectroscopy reveals the main broad peak at 770 cm-1, related to the A1g mode, which confirms the formation of cubic (ABO3 perovskite) structure. The single symmetric electron paramagnetic resonance (EPR) line shape with g = 2.13985 observed in PBFW was identified to be due to Fe3+ ions.

Effects of Sb Content (x) on (Bi(1-x)Sb(x))2Te3 Thermoelectric Thin Film Deposited by Effusion Cell Evaporator.

PubMed

Yong, Ho; Na, Sekwon; Gang, Jun-Gu; Jeon, Seong-Jae; Hyun, Seungmin; Lee, Hoo-Jeong

2015-10-01

This paper investigates the effects of the Sb content (x) on (Bi(1-x)Sb(x))2Te3 thermoelectric films with x changing widely from 0 (Sb2Te3) to 1 (Bi2Te3). First, the XRD analysis discloses that with the Sb content (x) increasing, the phase changed gradually from Bi2Te3 to Sb2Te3 as Sb atoms replaced substitutionally Bi atoms. Further microstructure analysis reveals that an extensive grain growth occurred during post-annealing for the samples with high Sb contents. According to the measurement of electrical and thermoelectric properties, the polarity of the charge carrier and Seebeck coefficient switched n-type to p-type in the range of x = 0.45~0.63. For the n-type samples, the power factor is highest when x = 0.18 around 46.01 μW/K(2) whereas Sb2Te3, for the p-type samples, shows the highest value, 62.48 μW/K(2)cm.

Electric field induced cubic to monoclinic phase transition in multiferroic 0.65Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-0.35PbTiO{sub 3} solid solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pandey, Rishikesh; Singh, Akhilesh Kumar, E-mail: akhilesh-bhu@yahoo.com

2014-10-20

The results of x-ray diffraction studies on 0.65Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-0.35PbTiO{sub 3} solid solution poled at various electric fields are presented. After poling, significant value of planar electromechanical coupling coefficient (k{sub P}) is observed for this composition having cubic structure in unpoled state. The cubic structure of 0.65Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-0.35PbTiO{sub 3} transforms to monoclinic structure with space group Pm for the poling field ≥5 kV/cm. Large c-axis microscopic lattice strain (1.6%) is achieved at 30 kV/cm poling field. The variation of the c-axis strain and unit cell volume with poling field shows a drastic jump similar to that observed for strainmore » versus electric field curve in (1 − x)Pb(Mg{sub 1/3}Nb{sub 2/3}) O{sub 3}-xPbTiO{sub 3} and (1 − x)Pb(Zn{sub 1/3}Nb{sub 2/3})O{sub 3}-xPbTiO{sub 3}.« less

Solar promoted azo dye degradation and energy production in the bio-photoelectrochemical system with a g-C3N4/BiOBr heterojunction photocathode

NASA Astrophysics Data System (ADS)

Hou, Yanping; Gan, Yuanyuan; Yu, Zebin; Chen, Xixi; Qian, Lun; Zhang, Boge; Huang, Lirong; Huang, Jun

2017-12-01

In this study, a single-chamber bio-photoelectrochemical system (BPES), integrating advantages of bioelectrochemical system and photocatalysis process, is developed using a g-C3N4/BiOBr heterojunction photocathode for methyl orange (MO) degradation and simultaneous energy recovery. Photocatalytic activities of g-C3N4/BiOBr, g-C3N4 and BiOBr are characterized by UV-vis diffuse reflectance spectra (UV-vis DRS) and Photoluminescence (PL) spectra; and electrochemical activities of photocathodes are examined by linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Results show that with an applied voltage of 0.8 V and under simulated solar irradiation, MO decolorization with g-C3N4/BiOBr photocathode reaches 97.8% within 4 h, higher than those with g-C3N4 (85.3%) and BiOBr (87.3%) photocathodes. Likewise, higher hydrogen production rate (143.8 L m-3d-1) is observed using g-C3N4/BiOBr photocathode; while values for g-C3N4 and BiOBr photocathodes are 124.3 L m-3d-1 and 117.1 L m-3d-1, respectively. PL and EIS reveal that superior performance of g-C3N4/BiOBr photocathode can be attributed to more efficient separation of photogenerated electron-hole pairs, lower resistance and better charge transfer. Synergistic effect occurs among biological, electrochemical and photocatalytic processes in illuminated BPES for MO removal. Photocathode optimization and system stability evaluation are conducted. This study demonstrates that the BPES holds great potential for efficient refractory organics degradation and energy production.

Antiferromagnetic Kondo lattice in the layered compound CePd 1 - x Bi 2 and comparison to the superconductor LaPd 1 - x Bi 2

DOE PAGES

Han, Fei; Wan, Xiangang; Phelan, Daniel; ...

2015-07-13

ZrCuSi 2-type CePd 1-xBi 2 crystals were obtained from excess Bi flux. Magnetic susceptibility measurements reveal that CePd 1-xBi 2 is a highly anisotropic antiferromagnet with transition temperature at 6 K, and a magnetic-field-induced metamagnetic transition at 5 T. An enhanced Sommerfeld coefficient of γ of 0.199 J-mol-Ce -1K -2 obtained from specific heat measurements suggests a moderate Kondo effect in CePd 1-xBi 2. In addition to the antiferromagnetic peak the resistivity curve shows a shoulder-like behavior which could be attributed to the presence of Kondo effect and crystal-electric-field effects in this compound. Magnetoresistance and Hall effect measurements suggest anmore » interplay between Kondo and crystal-electric-field effects which reconstructs the Fermi surface topology of CePd 1-xBi 2 around 75 K. Electronic structure calculations reveal the Pd vacancies are important to the magnetic structure and enhance the crystal-electric-field effects which quench the orbital moment of Ce at low temperatures.« less

Entanglement entropy and entanglement spectrum of Bi1-x Sb x (1 1 1) bilayers.

PubMed

Brzezińska, Marta; Bieniek, Maciej; Woźniak, Tomasz; Potasz, Paweł; Wójs, Arkadiusz

2018-02-28

We study topological properties of Bi 1-x Sb x bilayers in the (1 1 1) plane using entanglement measures. Electronic structures are investigated within multi-orbital tight-binding model and structural stability is confirmed through first-principles calculations. The topologically non-trivial nature of the bismuth bilayer is proved by the presence of spectral flow in the entanglement spectrum. We consider topological phase transitions driven by a composition change x, an applied external electric field in Bi bilayers and strain in Sb bilayers. Composition- and strain-induced phase transitions reveal a finite discontinuity in the entanglement entropy. This quantity remains a continuous function of the electric field strength, but shows a finite discontinuity in the first derivative. We relate the difference in behavior of the entanglement entropy to the breaking of inversion symmetry in the last case.

Entanglement entropy and entanglement spectrum of Bi1-x Sb x (1 1 1) bilayers

NASA Astrophysics Data System (ADS)

Brzezińska, Marta; Bieniek, Maciej; Woźniak, Tomasz; Potasz, Paweł; Wójs, Arkadiusz

2018-03-01

We study topological properties of Bi1-x Sb x bilayers in the (1 1 1) plane using entanglement measures. Electronic structures are investigated within multi-orbital tight-binding model and structural stability is confirmed through first-principles calculations. The topologically non-trivial nature of the bismuth bilayer is proved by the presence of spectral flow in the entanglement spectrum. We consider topological phase transitions driven by a composition change x, an applied external electric field in Bi bilayers and strain in Sb bilayers. Composition- and strain-induced phase transitions reveal a finite discontinuity in the entanglement entropy. This quantity remains a continuous function of the electric field strength, but shows a finite discontinuity in the first derivative. We relate the difference in behavior of the entanglement entropy to the breaking of inversion symmetry in the last case.

Superconductivity in Bi/Ni bilayer system: Clear role of superconducting phases found at Bi/Ni interface

NASA Astrophysics Data System (ADS)

Liu, L. Y.; Xing, Y. T.; Merino, I. L. C.; Micklitz, H.; Franceschini, D. F.; Baggio-Saitovitch, E.; Bell, D. C.; Solórzano, I. G.

2018-01-01

Bi/Ni bilayers with varying Bi and Ni layer thicknesses have been prepared by (a) pulsed-laser deposition (PLD) at 300 K and (b) thermal evaporation at 4.2 K. A two-step superconducting transition appears on the electrical transport measurements in the samples prepared by PLD. High-resolution transmission and scanning transmission electron microscopy, supported by energy-dispersive x-ray spectroscopy (EDXS) analysis, reveal that two superconducting intermetallic alloys, namely NiBi and NiBi3, are formed by interdiffusion, if the bilayers are prepared at 300 K. The Tc of the two phases behaves very differently in an external magnetic field and the upper critical magnetic fields at zero temperature [Bc 2(0 ) ] were estimated as 1.1 and 7.4 T, respectively. The lower value corresponds to the Bc 2(0) of NiBi3 phase and the higher one is supposed to be of NiBi. These alloys are responsible for the superconductivity and the two-step transition appearing in the Bi/Ni bilayer system. Surprisingly, the Bi-rich phase (NiBi3) is formed near the Ni layer, while the Ni-rich phase (NiBi) is formed far from the Ni layer. The EDXS analysis at nanometer scale clearly shows an unusual increase of Ni concentration near the interface of Bi/substrate. The limited thickness of Bi layer in the interdiffusion process results in an unexpected distribution of Ni concentration. Samples prepared at 4.2 K after annealing at 300 K do not show any superconductivity, which indicates that a nonepitaxial Bi/Ni interface does not induce superconductivity in the case interdiffusion does not occur. These results offer a deeper understanding of the superconductivity in the Bi/Ni bilayer system.

The BiCu{sub 1−x}OS oxysulfide: Copper deficiency and electronic properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berthebaud, D.; Guilmeau, E.; Lebedev, O.I.

2016-05-15

An oxysulfide series of nominal compositions BiCu{sub 1−x}OS with x<0.20 has been prepared and its structural properties characterized by combining powder X-ray diffraction and transmission electron microscopy techniques. It is found that this oxysulfide, crystallizing in the P4/nmm space group, tends to adopt a constant amount of copper vacancy corresponding to x=0.05 in the BiCu{sub 1−x}OS formula. The presence of Cu vacancies is confirmed by HAADF-STEM analysis showing, in the Cu atomic columns, alternating peaks of different intensities in some very localized regions. For larger Cu deficiencies (x>0.05 in the nominal composition), other types of structural nanodefects are evidenced suchmore » as bismuth oxysulfides of the “BiOS” ternary system which might explain the report of superconductivity for the BiCu{sub 1−x}OS oxysulfide. Local epitaxial growth of the BiCuOS oxysulfide on top of CuO is also observed. In marked contrast to the BiCu{sub 1−x}OSe oxyselenide, these results give an explanation to the limited impact of Cu deficiency on the Seebeck coefficient in BiCu{sub 1−x}OS compounds. - Graphical abstract: High resolution TEM image showing a Bi(Cu)OS/Bi{sub 2}O{sub 2}S interface and corresponding dislocation region. The Bi(Cu)OS structure adopts a rather constant Cu content (near 0.95); starting from BiCuOS leads to the formation of defects such as the Bi{sub 2}O{sub 2}S oxysulfide.« less

Physical properties of nanoparticles Nd added Bi1.7Pb0.3Sr2Ca2Cu3Oy superconductors

NASA Astrophysics Data System (ADS)

Abbas, Muna; Abdulridha, Ali; Jassim, Amal; Hashim, Fouad

2018-05-01

Bi1.7Pb0.3Sr2Ca2Cu3Oy bulks were synthesized, with the addition of Nd2O3 nanoparticles, by the solid state reaction method. The concentrations of Nd were varied from 0.1 to 0.6. The superconducting properties of the samples were investigated and studied to determine the influence of Nd2O3 addition on superconducting properties and microstructural development. The structural characteristics of the synthesized superconductor samples were carried out through X-ray diffractions. DC Four point probe method was used to study the electrical resistivity behavior and to evaluate the transition temperature (TC) for all samples. It was found that: 0.2 weight percentage of Nd2O3 yield the highest TC 123 K for highest volume fraction of 2223-phase, while excessive addition decreased both of them. The results point to compelling indications of correlations between charge carriers and superconductivity. Energy-dispersive X-ray spectroscopy (EDX) analysis for Bi1.7Pb0.3Nd0.2Sr2Ca2Cu3Oy superconductor shows that Nd may be substituted at Ca sites creating point defects, which act as flux pinning centers. Scanning electron microscopy (SEM) was employed to examine the microstructure of some samples. Their results showed precipitation of Nd nanoparticles on the surface as plate-like grains.

BI-2 destabilizes HIV-1 cores during infection and Prevents Binding of CPSF6 to the HIV-1 Capsid.

PubMed

Fricke, Thomas; Buffone, Cindy; Opp, Silvana; Valle-Casuso, Jose; Diaz-Griffero, Felipe

2014-12-11

The recently discovered small-molecule BI-2 potently blocks HIV-1 infection. BI-2 binds to the N-terminal domain of HIV-1 capsid. BI-2 utilizes the same capsid pocket used by the small molecule PF74. Although both drugs bind to the same pocket, it has been proposed that BI-2 uses a different mechanism to block HIV-1 infection when compared to PF74. This work demonstrates that BI-2 destabilizes the HIV-1 core during infection, and prevents the binding of the cellular factor CPSF6 to the HIV-1 core. Overall this short-form paper suggests that BI-2 is using a similar mechanism to the one used by PF74 to block HIV-1 infection.

Rietveld refinement and ionic conductivity of Ca{sub 8.4}Bi{sub 1.6}(PO{sub 4}){sub 6}O{sub 1.8}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tmar Trabelsi, I., E-mail: ilhem_tmar@yahoo.fr; Madani, A.; Mercier, A.M.

2013-01-15

The structure of Ca{sub 8.4}Bi{sub 1.6}(PO{sub 4}){sub 6}O{sub 1.8}, isostructural with Fluoroapatite, was determined by X-ray powder diffraction methods. The results of Rietveld refinement revealed that the formula of this compound is [Ca{sub 4}]{sup 4f}[Ca{sub 4.4}Bi{sub 1.6}]{sup 6h}(PO{sub 4}){sub 6}[O{sub 1.8}]{sup 2a}, space group P63/m (a=9.468 (3) A, c=6.957 (3) A). A total substitution of Bi{sup 3+} ions in the (6h) sites was related particularly to the high polarizability of the Bi{sup 3+} ion compared to Ca{sup 2+}. The observed frequencies in the Raman and infrared spectra were explained and discussed on the basis of unit-cell group analyses and inmore » comparison with Fluoroapatite and other oxyapatites. The ionic conductivity over a wide range of temperature was investigated according to the complex impedance method. The highest overall conductivity values were found at {sigma}{sub 700 Degree-Sign C} =5.03 Multiplication-Sign 10{sup -7} S cm{sup -1} and E{sub a}=0.50 eV. - Graphical abstract: The final Rietveld refinement plot of the Ca{sub 8.4}Bi{sub 1.6} (PO{sub 4}){sub 6}O{sub 1.8}. Highlights: Black-Right-Pointing-Pointer The Rietveld refinement revealed that the formula of this compound is Ca{sub 8.4}Bi{sub 1.6}(PO{sub 4}){sub 6}O{sub 1.8}. Black-Right-Pointing-Pointer Vibrational spectroscopy supports the high symmetry P63/m space group for this apatite. Black-Right-Pointing-Pointer This apatite contained channels where oxygen ions were located in 2a sites. Black-Right-Pointing-Pointer The possibility of anionic conduction along these channels was considered.« less

Fabrication and Piezoelectric Properties of Textured (Bi1/2K1/2)TiO3 Ferroelectric Ceramics

NASA Astrophysics Data System (ADS)

Nagata, Hajime; Saitoh, Masahiro; Hiruma, Yuji; Takenaka, Tadashi

2010-09-01

Textured (Bi1/2K1/2)TiO3 (BKT) ceramics were prepared by a reactive templated grain growth (RTGG) method to improve their piezoelectric properties. Also, a hot-pressing (HP) method was modified on the basis of RTGG method to obtain dense ceramics and promote the grain orientation. The textured BKT ceramics prepared by the RTGG and HP methods exhibited a relatively high orientation factor F of 0.82 and a high density ratio of 95-99%. Scanning electron microscopy (SEM) micrographs of the textured HP-BKT indicated a textured and poreless microstructure. In addition, the resistivity of the textured HP-BKT was 1.73×1013 Ω·cm. The piezoelectric strain constant d33 determined by means of resonance and antiresonance method was 125 pC/N for the direction parallel to the sheet-stacking direction of the RTGG process. From the measurement of field-induced stain, the normalized d33* (=Smax/Emax) at 80 kV/cm were 127 and 238 pm/V on the randomly oriented and textured samples (F=0.82) for the (∥) direction, respectively.

Plasmon Enhancement of Photoinduced Resistivity Changes in Bi1-xCaxMnO3 Thin Films

NASA Astrophysics Data System (ADS)

Smolyaninova, Vera; Talanova, E.; Kolagani, Rajeswari; Yong, G.; Kennedy, R.; Steger, M.; Wall, K.

2007-03-01

Doped rare-earth manganese oxides (manganites) exhibit a wide variety of physical phenomena due to complex interplay of electronic, magnetic, orbital, and structural degrees of freedom and their sensitivity to external fields. A photoinduced insulator to conductor transition in charge-ordered manganites is especially interesting from the point of view of creating photonic devices. Thin films of Bi0.4Ca0.6MnO3 exhibit large photoinduced resistivity changes associated with melting of the charge ordering by visible light [1]. We have found a considerable increase of the photoinduced resistivity changes in the Bi0.4Ca0.6MnO3 thin film after depositing metal nanoparticles on the surface. This increase can be explained by enhancement of local electromagnetic field in the vicinity of the gold nanoparticle due to the plasmon resonance. The changes in lifetime of the photoinduced state will be reported, and the possible origin of these effects will be discussed. [1] V. N. Smolyaninova at al., Appl. Phys. Lett. 86, 071922 (2005).

Unification of the negative electrocaloric effect in Bi{sub 1/2}Na{sub 1/2}TiO{sub 3}-BaTiO{sub 3} solid solutions by Ba{sub 1/2}Sr{sub 1/2}TiO{sub 3} doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uddin, Sarir; Materials Research Laboratory, Institute of Physics and Electronics, University of Peshawar, Peshawar 25120; Zheng, Guang-Ping, E-mail: mmzheng@polyu.edu.hk

2013-12-07

The microscopic mechanisms of the negative electrocaloric effect (ECE) of the single-phase (1−x)(0.94Bi{sub 1/2}Na{sub 1/2}TiO{sub 3}-0.06BaTiO{sub 3})-xBa{sub 1/2}Sr{sub 1/2}TiO{sub 3} (BNT-BT-BST) perovskite solid solutions fabricated via the sol-gel technique are explored in this study. Dielectric and mechanical relaxation analyses are employed to investigate the ferroelectric and structural transitions of the samples. The electrocaloric properties of the samples were measured by thermodynamics Maxwell relations. The difference between the depolarization temperature (T{sub d}) and the maximum dielectric constant temperature (T{sub m}) was found to decrease with increasing BST content. Doping with BST stabilized the ferroelectric phase along with unifying the EC temperaturemore » changes (ΔT) to only negative values. The origin of the uniform negative ECE of BNT-BT-BST is discussed.« less

Influence of Bi-related impurity states on the bandgap and spin-orbit splitting energy of dilute III-V-Bi alloys: InP1-xBix, InAs1-xBix, InSb1-xBix and GaSb1-xBix

NASA Astrophysics Data System (ADS)

Samajdar, D. P.; Dhar, S.

2016-01-01

Valence Band Anticrossing (VBAC) Model is used to calculate the changes in band structure of Bi containing alloys such as InP1-xBix, InAs1-xBix, InSb1-xBix and GaSb1-xBix due to the incorporation of dilute concentrations of bismuth. The coupling parameter CBi which gives the magnitude of interaction of Bi impurity states with the LH, HH and SO sub bands in VBAC depends on the increase in the HH/LH related energy level EHH/LH+, location of the Bi related impurity level EBi and valence band offset ΔEVBM between the endpoint compounds in the corresponding III-V-Bi. The reduction in band gap as well as the enhancement of the spin-orbit splitting energy is well explained using this model and the calculated results are compared with the results of Virtual Crystal Approximation (VCA) and Density Functional Theory (DFT) calculations, as well as with the available experimental data and are found to have good agreement. The incorporation of Bi mainly perturbs the valence band due to the interaction of the Bi impurity states with the HH, LH and SO bands. The lowering of the conduction band minimum (CBM) due to VCA is added with the upward movement of the HH/LH bands to get the total reduction in band gap for the bismides. The valence band shifts of 31.9, 32.5, 20.8 and 12.4 meV/at%Bi for InP1-xBix, InAs1-xBix, InSb1-xBix and GaSb1-xBix respectively constitute 65, 76, 59 and 31% of the total band gap reduction and the rest is the contribution of the conduction band shift. The spin-orbit splitting energy also shows significant increase with the maximum change in InPBi and the minimum in InSbBi. The same is true for Ga containing bismides if we make a comparison with the available values for GaAsBi and GaPBi with that of GaSbBi. It has also been observed that the increase in splitting energy is greater in case of the bismides such as InAsBi, InPBi and GaAsBi than the bismides such as InSbBi and GaSbBi with the parent substrates having higher values of splitting energy. This may

Substitution-induced spin-splitted surface states in topological insulator (Bi1−xSbx)2Te3

PubMed Central

He, Xiaoyue; Li, Hui; Chen, Lan; Wu, Kehui

2015-01-01

We present a study on surface states of topological insulator (Bi1−xSbx)2Te3 by imaging quasiparticle interference patterns (QPI) using low temperature scanning tunneling microscope. Besides the topological Dirac state, we observed another surface state with chiral spin texture within the conduction band range. The quasiparticle scattering in this state is selectively suppressed. Combined with first-principles calculations, we attribute this state to a spin-splitted band induced by the substitution of Bi with Sb atoms. Our results demonstrate that the coexistence of topological order and alloying may open wider tunability in quantum materials. PMID:25743262

Electrical conductivity and thermopower of (1 - x) BiFeO(3) - xBi(0.5)K(0.5)TiO3 (x = 0.1, 0.2) ceramics near the ferroelectric to paraelectric phase transition.

PubMed

Wefring, E T; Einarsrud, M-A; Grande, T

2015-04-14

Ferroelectric BiFeO3 has attractive properties such as high strain and polarization, but a wide range of applications of bulk BiFeO3 are hindered due to high leakage currents and a high coercive electric field. Here, we report on the thermal behaviour of the electrical conductivity and thermopower of BiFeO3 substituted with 10 and 20 mol% Bi0.5K0.5TiO3. A change from p-type to n-type conductivity in these semi-conducting materials was demonstrated by the change in the sign of the Seebeck coefficient and the change in the slope of the isothermal conductivity versus partial pressure of O. A minimum in the isothermal conductivity was observed at ∼10(-2) bar O2 partial pressure for both solid solutions. The strong dependence of the conductivity on the partial pressure of O2 was rationalized by a point defect model describing qualitatively the conductivity involving oxidation/reduction of Fe(3+), the dominating oxidation state of Fe in stoichiometric BiFeO3. The ferroelectric to paraelectric phase transition of 80 and 90 mol% BiFeO3 was observed at 648 ± 15 and 723 ± 15 °C respectively by differential thermal analysis and confirmed by dielectric spectroscopy and high temperature powder X-ray diffraction.

Structural investigation of (111) oriented (BiFeO3)(1-x)Λ/(LaFeO3)xΛ superlattices by X-ray diffraction and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Belhadi, J.; Yousfi, S.; Bouyanfif, H.; El Marssi, M.

2018-04-01

(BiFeO3)(1-x)Λ/(LaFeO3)xΛ superlattices (SLs) with varying x have been grown by pulsed laser deposition on (111) oriented SrTiO3 substrates. In order to obtain good epitaxy and flat samples, a conducting SrRuO3 buffer has been deposited prior to the superlattices to screen the polar mismatch for such (111) SrTiO3 orientation. X-ray diffraction reciprocal space mapping on a different family of planes was collected and evidenced a room temperature structural change at x = 0.5 from a rhombohedral/monoclinic structure for rich BiFeO3 to an orthorhombic symmetry for rich LaFeO3. This symmetry change has been confirmed by Raman spectroscopy and demonstrates the different phase stability compared to similar SLs grown on (100) SrTiO3. The strongly anisotropic strain and oxygen octahedral rotation/tilt system compatibility at the interfaces probably explain the orientation dependence of the phase stability in such superlattices.

Gate-Variable Mid-Infrared Optical Transitions in a (Bi1-xSbx)2Te3 Topological Insulator.

PubMed

Whitney, William S; Brar, Victor W; Ou, Yunbo; Shao, Yinming; Davoyan, Artur R; Basov, D N; He, Ke; Xue, Qi-Kun; Atwater, Harry A

2017-01-11

We report mid-infrared spectroscopy measurements of ultrathin, electrostatically gated (Bi 1-x Sb x ) 2 Te 3 topological insulator films in which we observe several percent modulation of transmittance and reflectance as gating shifts the Fermi level. Infrared transmittance measurements of gated films were enabled by use of an epitaxial lift-off method for large-area transfer of topological insulator films from infrared-absorbing SrTiO 3 growth substrates to thermal oxidized silicon substrates. We combine these optical experiments with transport measurements and angle-resolved photoemission spectroscopy to identify the observed spectral modulation as a gate-driven transfer of spectral weight between both bulk and 2D topological surface channels and interband and intraband channels. We develop a model for the complex permittivity of gated (Bi 1-x Sb x ) 2 Te 3 and find a good match to our experimental data. These results open the path for layered topological insulator materials as a new candidate for tunable, ultrathin infrared optics and highlight the possibility of switching topological optoelectronic phenomena between bulk and spin-polarized surface regimes.

Superconductivity in the orthorhombic phase of thermoelectric CsPb{sub x}Bi{sub 4−x}Te{sub 6} with 0.3≤x≤1.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, R.X.; Yang, H.X., E-mail: hxyang@iphy.ac.cn; Tian, H.F.

2015-12-15

Experimental measurements clearly reveal the presence of bulk superconductivity in the CsPb{sub x}Bi{sub 4−x}Te{sub 6} (0.3≤x≤1.0) materials, i.e. the first member of the thermoelectric series of Cs[Pb{sub m}Bi{sub 3}Te{sub 5+m}], these materials have the layered orthorhombic structure containing infinite anionic [PbBi{sub 3}Te{sub 6}]{sup −} slabs separated with Cs{sup +} cations. Temperature dependences of electrical resistivity, magnetic susceptibility, and specific heat have consistently demonstrated that the superconducting transition in Cs{sub 0.96}Pb{sub 0.25}Bi{sub 3.75}Te{sub 6.04} occurs at T{sub c}=3.1 K, with a superconducting volume fraction close to 100% at 1.8 K. Structural study using aberration-corrected STEM/TEM reveals a rich variety of microstructuralmore » phenomena in correlation with the Pb-ordering and chemical inhomogeneity. The superconducting material Cs{sub 0.96}Pb{sub 0.25}Bi{sub 3.75}Te{sub 6.04} with the highest T{sub c} shows a clear ordered structure with a modulation wave vector of q≈a*/2+c*/1.35 on the a–c plane. Our study evidently demonstrates that superconductivity deriving upon doping of narrow-gap semiconductor is a viable approach for exploration of novel superconductors. - Graphical abstract: Bulk superconductivity is discovered in the orthorhombic Cs{sub 0.96}Pb{sub 0.22}Bi{sub 3.80}Te{sub 6.02} materials with the superconducting transition T{sub c}=3.1 K. The compound shows a clear ordered structure with a modulation wave vector of q≈a*/2+c*/1.35 on the a–c plane. - Highlights: • Bulk superconductivity is discovered in the orthorhombic CsPb{sub x}Bi{sub 4−x}Te{sub 6} materials. • The superconducting transition in Cs{sub 0.96}Pb{sub 0.22}Bi{sub 3.80}Te{sub 6.02} occurs at T{sub c}=3.1 K. • Physical property measurements concerning the bulk superconductivity were present. • Structural modulation due to Pb-ordering was observed.« less

Thermoelectric Properties of Cu-doped Bi0.4Sb1.6Te3 Prepared by Hot Extrusion

NASA Astrophysics Data System (ADS)

Jung, Woo-Jin; Kim, Il-Ho

2018-06-01

Cu0.003Bi0.4Sb1.6Te3 alloys were prepared by using encapsulated melting and hot extrusion (HE). The hot-extruded specimens had the relative average density of 98%. The ( 00l) planes were preferentially oriented parallel to the extrusion direction, but the specimens showed low crystallographic anisotropy with low orientation factors. The specimens were hot-extruded at 698 K, and they showed excellent mechanical properties with a Vickers hardness of 76 Hv and a bending strength of 59 MPa. However, as the HE temperature increased, the mechanical properties degraded due to grain growth. The hot-extruded specimens showed positive Seebeck coefficients, indicating that the specimens have p-type conduction. These specimens exhibited negative temperature dependences of electrical conductivity, and thus behaved as degenerate semiconductors. The Seebeck coefficient reached the maximum value at 373 K and then decreased with increasing temperature due to intrinsic conduction. Cu-doped specimens exhibited high power factors due to relatively higher electrical conductivities and Seebeck coefficients than those of undoped specimens. A thermal conductivity of 1.00 Wm-1 K-1 was obtained at 373 K for Cu0.003Bi0.4Sb1.6Te3 hot-extruded at 723 K. A maximum dimensionless figure of merit, ZT max = 1.05, and an average dimensionless figure of merit, ZT ave = 0.98, were achieved at 373 K.

Phase Equilibria and Crystal Chemistry in Portions of the System SrO-CaO-Bi2O3-CuO, Part IV— The System CaO-Bi2O3-CuO

PubMed Central

Burton, B. P.; Rawn, C. J.; Roth, R. S.; Hwang, N. M.

1993-01-01

New data are presented on the phase equilibria and crystal chemistry of the binary systems CaO-Bi2O3 and CaO-CuO and the ternary CaO-Bi2O3-CuO. Symmetry data and unit cell dimensions based on single crystal and powder x-ray diffraction measurements are reported for several of the binary CaO-Bi2O3 phases, including corrected compositions for Ca4Bi6O13 and Ca2Bi2O5. The ternary system contains no new ternary phases which can be formed in air at ~700–900 °C. PMID:28053484

Effect of disappearance of rhombohedral phase on the dielectric properties of novel BiFe1-xCoxO3

NASA Astrophysics Data System (ADS)

Tiwary, S.; Kuila, S.; Sahoo, M. R.; Barik, A.; Vishwakarma, P. N.

2018-04-01

Through this report, we intend to highlight the effect of R3c phase in the BiFe1-xCoxO3: x=33, 34. Study of impedance and modulus spectra points towards lower activation energy of resistance as compared to capacitance relaxation, as the cause for finite conductivity at near and above room temperature. Magnetodielectric study shows decrease in its value by half, because of absence of R3c phase in the sample. Due to absence of R3c phase, the activation energy of capacitance relaxation is also found to increase by three times. It thus shows that R3c phase is very important for having capacitance relaxation in this sample system.

Tuning the giant magnetoelastic transition in Ba3BiIr2O9 and Ba3BiRu2O9

NASA Astrophysics Data System (ADS)

Huang, Zixin; Avdeev, Maxim; Kennedy, Brendan J.; Knight, Kevin S.; Zhou, Qingdi; Ling, Chris D.

2014-07-01

We have experimentally investigated the effects of pressure on the magnetoelastic transitions associated with the opening of spin-gaps in Ba3BiIr2O9 and Ba3BiRu2O9. For both compounds, reducing the unit cell volume by either external physical and internal chemical pressure was found to reduce the temperature T* of the transition and, to a lesser extent, the magnitude of the associated negative thermal volume expansion. The results yield the latent heat associated with the transitions, -3.34(3) × 102 J mol-1 for Ba3BiIr2O9 and -7.1(5) × 102 J mol-1 for Ba3BiRu2O9. The transition in Ba3BiRu2O9 is significantly more robust than in Ba3BiIr2O9, requiring an order of magnitude higher pressures to achieve the same reduction in T*. The differing responses of the two compounds points to differences between the 4d and 5d metals and hence to the importance of spin-orbit coupling, which is expected to be much stronger in the Ir compound.

High pressure X-ray diffraction studies on Bi2-xSbxTe3 (x=0,1,2) materials

NASA Astrophysics Data System (ADS)

Jacobsen, Matthew; Kumar, Ravhi; Cornelius, Andrew

2007-06-01

Recently Bi2Te3 based thermoelectric materials have gained importance due to their high thermoelectric figure of merit in thin films [3]. Pressure tuning of the thermoelectric figure of merit has been reported for several materials [1],[2]. In order to investigate the bulk properties of Bi2Te3, Sb2Te3, and their solid solution in detail, we have performed structural studies up to 20 GPa. Our diffraction results show that all three compounds transform from the ambient pressure structure to a high pressure phase between 5 and 7 GPa. Details of the results will be discussed in this presentation. [1]Chen, G., Dresselhaus, M.S., Dresselhaus, G., Fleurial, J.-P., and Caillat, T. Recent developments in themoelectric materials. International Materials Reviews, 48, 45-66 (2003). [2]Rowe, D.M. CRC Handbook of Thermoelectric Materials. CRC Press, 1995. [3]Venkatasubramanian, R., Silvola, E., Colpitts, T., and O'Quinn, B. Thin-film thermoelectric devices with high room-temperature figures of merit. Nature, 413, 597-602, 2001.

Giant Polarization and High Temperature Monoclinic Phase in a Lead-Free Perovskite of Bi(Zn 0.5Ti 0.5)O 3-BiFeO 3

DOE PAGES

Pan, Zhao; Chen, Jun; Yu, Runze; ...

2016-09-15

Lead-free piezoelectrics have attracted increasing attention due to the awareness of lead toxicity to the environment. Here, a new Bi-based lead-free perovskite of (1-x)Bi(Zn 0.5Ti 0.5)O 3-xBiFeO 3 has been synthesized via high-pressure and high-temperature method. It exhibits interest-ing properties of giant polarization, morphotropic phase boundary (MPB), and monoclinic phase. In particular, large tetragonality ( c/a = 1.228) and giant spontaneous polariza-tion of 110 μC/cm 2 has been obtained in 0.6Bi(Zn 0.5Ti 0.5)O 3-0.4BiFeO 3, which is much higher than most available lead-free materials and conventional Pb(Zr,Ti)O 3. MPB is clearly identified to be constituted by tetragonal and monoclinic phasesmore » at x = 0.5. Notably, a single monoclinic phase has been observed at x = 0.6, which exhibits an intriguing high temperature property. In conclusion, the present results are helpful to explore new lead-free MPB systems in bismuth-based compounds.« less

Low-Temperature Bonding of Bi0.5Sb1.5Te3 Thermoelectric Material with Cu Electrodes Using a Thin-Film In Interlayer

NASA Astrophysics Data System (ADS)

Lin, Yan-Cheng; Yang, Chung-Lin; Huang, Jing-Yi; Jain, Chao-Chi; Hwang, Jen-Dong; Chu, Hsu-Shen; Chen, Sheng-Chi; Chuang, Tung-Han

2016-09-01

A Bi0.5Sb1.5Te3 thermoelectric material electroplated with a Ni barrier layer and a Ag reaction layer was bonded with a Ag-coated Cu electrode at low temperatures of 448 K (175 °C) to 523 K (250 °C) using a 4- μm-thick In interlayer under an external pressure of 3 MPa. During the bonding process, the In thin film reacted with the Ag layer to form a double layer of Ag3In and Ag2In intermetallic compounds. No reaction occurred at the Bi0.5Sb1.5Te3/Ni interface, which resulted in low bonding strengths of about 3.2 MPa. The adhesion of the Bi0.5Sb1.5Te3/Ni interface was improved by precoating a 1- μm Sn film on the surface of the thermoelectric element and preheating it at 523 K (250 °C) for 3 minutes. In this case, the bonding strengths increased to a range of 9.1 to 11.5 MPa after bonding at 473 K (200 °C) for 5 to 60 minutes, and the shear-tested specimens fractured with cleavage characteristics in the interior of the thermoelectric material. The bonding at 448 K (175 °C) led to shear strengths ranging from 7.1 to 8.5 MPa for various bonding times between 5 and 60 minutes, which were further increased to the values of 10.4 to 11.7 MPa by increasing the bonding pressure to 9.8 MPa. The shear strengths of Bi0.5Sb1.5Te3/Cu joints bonded with the optimized conditions of the modified solid-liquid interdiffusion bonding process changed only slightly after long-term exposure at 473 K (200 °C) for 1000 hours.

Preparation, electronic structure, and chemical bonding of lead-free (1 - x)(K0.5Bi0.5)TiO3- xBaTiO3 solid solution

NASA Astrophysics Data System (ADS)

Sasikumar, S.; Saravanan, R.; Saravanakumar, S.; Robert, M. Charles

2018-01-01

Polycrystalline lead-free (1 - x)(K0.5Bi0.5)TiO3- xBaTiO3, ((1 - x)KBT- xBT) ( x = 0.00, 0.08, 0.12) ceramics were synthesized via solid-state reaction method. The powder X-ray diffraction (PXRD) and structural refinement results confirm that a single-phase tetragonal structure with space group P4mm. Charge density distribution inside the unit cell of (1 - x)KBT- xBT was investigated by the maximum entropy method. Charge density analysis reveals the reduction in ionic nature along K/Bi-O bond and enhancement of covalent nature along Ti-O bond with the addition of BaTiO3. The charge density distribution studies done using maximum entropy method for (1 - x)KBT- xBT have not been done so far. The surface morphology study was done using scanning electron microscopy (SEM). Energy dispersive X-rays spectra (EDS) were used to investigate the elemental compositions present in the system. The dielectric constant and loss tangent were studied as a function of frequency. The dielectric constant and loss were decreased with increase of frequency. Room temperature dielectric constant ( ɛ) and loss (tan δ) were measured for x = 0.00 about 511 and 0.51, respectively, at a frequency of 10 kHz.

High-K (Ba0.8Bi0.2)(Zn0.1Ti0.9)O3 ceramics for high-temperature capacitor applications.

PubMed

Raengthon, Natthaphon; Cann, David P

2011-09-01

Solid solutions of BaTiO(3)-Bi(Zn(1/2)Ti(1/2))O(3) were investigated for high-temperature capacitor applications. Compositions close to 0.8BaTiO(3)-0.2Bi(Zn(1/2)Ti(1/2))O(3) revealed pseudo-cubic symmetry and showed a linear dielectric response. The existence of a nearly flat temperature dependence of the relative permittivity over the temperature range of 100 to 350°C was also obtained. In this study, the effects of cation non-stoichiometry and doping were investigated in an attempt to optimize the insulation resistance for high-temperature applications. The dielectric response of (Ba(0.8)-xBi(0.2))(Zn(0.1)Ti(0.9)) O(3) ceramics where 0 ≤ X ≤ 0.08, as well as ZrO2- and Mn(2)O(3)-doped ceramics were studied. The optimum compositions exhibited a relative permittivity in excess of 1150 with a low loss tangent (tan δ < 0.05) that persisted up to a temperature of 460δC. The temperature dependence of resistivity also revealed the improved insulation resistance of Ba-deficient compositions. Additionally, we suggest that an ionic conduction mechanism is responsible for the degradation of resistivity at high temperatures. The temperature coefficient of permittivity ((τ)K) and the RC time constant were also investigated.

Experimental and numerical study on transverse piezoelectricity of xBiInO3-(1 - x)PbTiO3 films by multilayer cantilevers

NASA Astrophysics Data System (ADS)

Sun, Ke-xue; Zhang, Shu-yi; Shui, Xiu-ji; Wasa, Kiyotaka

2018-02-01

The effective transverse piezoelectric coefficient of the piezoelectric films xBiInO3-(1 - x)PbTiO3 (x = 0,0.10,0.15,0.20) were studied experimentally and numerically by multilayer cantilevers. The xBiInO3-(1 - x)PbTiO3 thin films were deposited on (101)SrRuO3/(100)Pt/(100)MgO substrates and then covered with Pt electrode by RF-magnetron sputtering method. In experiments, the tip vibration amplitudes of the cantilevers for different x of the films were measured, in which the optimized compositions for maximizing the tip vibration can be found. Meanwhile, based on the bending model of multilayer piezoelectric cantilevers, the tip-deflection and transverse piezoelectricity of the cantilevers were simulated by COMSOL software. By comparing the experimental and numerical results, both are in agreement very well, and the mechanism of the optimized transverse piezoelectricity of the cantilevers was proposed finally.

Determination of nucleic acids based on the quenching effect on resonance light scattering of the Y(III)-1,6-bi(1'-phenyl-3'-methyl-5'-pyrazolone-4'-)hexane-dione system.

PubMed

Wu, Xia; Yang, Jing He; Sun, Shuna; Guo, Changying; Ran, Dehuan; Zheng, Jinhua

2006-01-01

Nucleic acids can quench resonance light scattering (RLS) intensity of the Y(III)-1,6-bi(1'-phenyl-3'-methyl-5'-pyrazolone-4'-)hexane-dione(BPMPHD) complex in the pH range 5.0-5.8. Under optimal conditions, there are linear relationships between the quenching of RLS and the concentration of nucleic acids in the range 6.3 x 10(-8)-2.1 x 10(-5) g/mL for fish sperm DNA (fsDNA), 1.2 x 10(-8)-5.0 x 10(-5) g/mL for calf thymus DNA (ctDNA) and 6.0 x 10(-8)-2.0 x 10(-5) g/mL for yeast RNA (yRNA). The detection limits (3 s) of fsDNA, ctDNA and yRNA are 0.7 ng/mL, 3.8 ng/mL and 4.2 ng/mL, respectively. Copyright (c) 2006 John Wiley & Sons, Ltd.

Analytical Solutions for the Surface States of Bi1-xSbx (0 ≤ x ≲ 0.1)

NASA Astrophysics Data System (ADS)

Fuseya, Yuki; Fukuyama, Hidetoshi

2018-04-01

Analytical solutions for the surface state (SS) of an extended Wolff Hamiltonian, which is a common Hamiltonian for strongly spin-orbit coupled systems, are obtained both for semi-infinite and finite-thickness boundary conditions. For the semi-infinite system, there are two types of SS solutions: (I-a) linearly crossing SSs in the direct bulk band gap, and (I-b) SSs with linear dispersions entering the bulk conduction or valence bands away from the band edge. For the finite-thickness system, a gap opens in the SS of solution I-a. Numerical solutions for the SS are also obtained based on the tight-binding model of Liu and Allen [Phys. Rev. B 52, 1566 (1995)] for Bi1-xSbx (0 ≤ x ≤ 0.1). A perfect correspondence between the analytic and numerical solutions is obtained around the \\bar{M} point including their thickness dependence. This is the first time that the character of the SS numerically obtained is identified with the help of analytical solutions. The size of the gap for I-a SS can be larger than that of bulk band gap even for a "thick" films ( ≲ 200 bilayers ≃ 80 nm) of pure bismuth. Consequently, in such a film of Bi1-xSbx, there is no apparent change in the SSs through the band inversion at x ≃ 0.04, even though the nature of the SS is changed from solution I-a to I-b. Based on our theoretical results, the experimental results on the SS of Bi1-xSbx (0 ≤ x ≲ 0.1) are discussed.

Superconductivity versus structural phase transition in the closely related Bi 2Rh 3.5S 2 and Bi 2Rh 3S 2

DOE PAGES

Kaluarachchi, Udhara S.; Xie, Weiwei; Lin, Qisheng; ...

2015-05-19

Single crystals of Bi 2Rh 3S 2 and Bi 2Rh 3.5S 2 were synthesized by solution growth, and the crystal structures and thermodynamic and transport properties of both compounds were studied. In the case of Bi 2Rh 3S 2, a structural first-order transition at around 165 K is identified by single-crystal diffraction experiments, with clear signatures visible in resistivity, magnetization, and specific heat data. No superconducting transition for Bi 2Rh 3S 2 was observed down to 0.5 K. In contrast, no structural phase transition at high temperature was observed for Bi 2Rh 3.5S 2; however, bulk superconductivity with a criticalmore » temperature, T c ≈ 1.7 K, was observed. The Sommerfeld coefficient γ and the Debye temperature (Θ D) were found to be 9.41 mJ mol –1K –2 and 209 K, respectively, for Bi 2Rh 3S 2, and 22 mJ mol –1K –2 and 196 K, respectively, for Bi 2Rh 3.5S 2. As a result, the study of the specific heat in the superconducting state of Bi 2Rh 3.5S 2 suggests that Bi 2Rh 3.5S 2 is a weakly coupled, BCS superconductor.« less

FTIR characterization of Bi2Sr2Can-1(Cu1-xFex)3O10+δ with (n=3, x = 0.01) ceramic superconductor

NASA Astrophysics Data System (ADS)

Kumar, Rohitash; Singh, H. S.; Singh, Yadunath

2018-05-01

We synthesized a ceramic superconductor Bi2Sr2Can-1(Cu1-xFex)3O10+δ with (n = 3, x = 0.01) by usual method of oxides superconductor. In this paper, we report the characterization of the said sample by Fourier Transform Infrared Spectroscopic (FTIR) method. This method provides information about structural and compound bonding formation for the studied sample in powder form. The sharper peaks in the recorded spectra are reflecting with a functional group in the high-frequency stretching and low frequency bending modes. In this study, the interaction between Cu-O and Fe-O bond occupies octahedral and tetrahedral positions due to occupancy of cations and anions. The increasing amount of (Fe) is showing the transmittance (T%) behavior with different bonding vibration modes.

Tuning the giant magnetoelastic transition in Ba3BiIr2O9 and Ba3BiRu2O9.

PubMed

Huang, Zixin; Avdeev, Maxim; Kennedy, Brendan J; Knight, Kevin S; Zhou, Qingdi; Ling, Chris D

2014-07-09

We have experimentally investigated the effects of pressure on the magnetoelastic transitions associated with the opening of spin-gaps in Ba3BiIr2O9 and Ba3BiRu2O9. For both compounds, reducing the unit cell volume by either external physical and internal chemical pressure was found to reduce the temperature T(*) of the transition and, to a lesser extent, the magnitude of the associated negative thermal volume expansion. The results yield the latent heat associated with the transitions, -3.34(3) × 10(2) J mol(-1) for Ba3BiIr2O9 and -7.1(5) × 10(2) J mol(-1) for Ba3BiRu2O9. The transition in Ba3BiRu2O9 is significantly more robust than in Ba3BiIr2O9, requiring an order of magnitude higher pressures to achieve the same reduction in T(*). The differing responses of the two compounds points to differences between the 4d and 5d metals and hence to the importance of spin-orbit coupling, which is expected to be much stronger in the Ir compound.

Collective vortex pinning and merging of the irreversibility line and second peak effect in optimally doped Ba1-xKxBiO3 single crystals

NASA Astrophysics Data System (ADS)

Jiao, Yanjing; Cheng, Wang; Deng, Qiang; Yang, Huan; Wen, Hai-Hu

2018-02-01

Measurements on magnetization and relaxation have been carried out on an optimally doped Ba1-xKxBiO3+δ single crystal with Tc = 31.3 K. Detailed analysis is undertaken on the data. Both the dynamical relaxation and conventional relaxation have been measured leading to the self-consistent determination of the magnetization relaxation rate. It is found that the data are well described by the collective pinning model leading to the glassy exponent of about μ ≈ 1.64-1.68 with the magnetic fields of 1 and 3 T. The analysis based on Maley's method combining with the conventional relaxation data allows us to determine the current dependent activation energy U which yields a μ value of about 1.23-1.29 for the magnetic fields of 1 and 3 T. The second magnetization peaks appear in wide temperature region from 2 K to 24 K. The separation between the second peak field and the irreversibility field becomes narrow when temperature is increased. When the two fields are close to each other, we find that the second peak evolves into a step-like transition of magnetization. Finally, we present a vortex phase diagram and demonstrate that the vortex dynamics in Ba1-xKxBiO3 can be used as a model system for studying the collective vortex pining.

Giant strain with low cycling degradation in Ta-doped [Bi{sub 1/2}(Na{sub 0.8}K{sub 0.2}){sub 1/2}]TiO{sub 3} lead-free ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Xiaoming; Tan, Xiaoli, E-mail: xtan@iastate.edu

2016-07-21

Non-textured polycrystalline [Bi{sub 1/2}(Na{sub 0.8}K{sub 0.2}){sub 1/2}](Ti{sub 1−x}Ta{sub x})O{sub 3} ceramics are fabricated and their microstructures and electrical properties are characterized. Transmission electron microscopy reveals the coexistence of the rhombohedral R3c and tetragonal P4bm phases in the form of nanometer-sized domains in [Bi{sub 1/2}(Na{sub 0.8}K{sub 0.2}){sub 1/2}]TiO{sub 3} with low Ta concentration. When the composition is x = 0.015, the electrostrain is found to be highly asymmetric under bipolar fields of ±50 kV/cm. A very large value of 0.62% is observed in this ceramic, corresponding to a large-signal piezoelectric coefficient d{sub 33}* of 1240 pm/V (1120 pm/V under unipolar loading). These values are greater thanmore » most previously reported lead-free polycrystalline ceramics and can even be compared with some lead-free piezoelectric single crystals. Additionally, this ceramic displays low cycling degradation; its electrostrain remains above 0.55% even after undergoing 10 000 cycles of ±50 kV/cm bipolar fields at 2 Hz. Therefore, Ta-doped [Bi{sub 1/2}(Na{sub 0.8}K{sub 0.2}){sub 1/2}]TiO{sub 3} ceramics show great potential for large displacement devices.« less

Electric-field-induced strain contributions in morphotropic phase boundary composition of (Bi{sub 1/2}Na{sub 1/2})TiO{sub 3}-BaTiO{sub 3} during poling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khansur, Neamul H.; Daniels, John E.; Hinterstein, Manuel

2015-12-14

The microscopic contributions to the electric-field-induced macroscopic strain in a morphotropic 0.93(Bi{sub 1/2}Na{sub 1/2}TiO{sub 3})−0.07(BaTiO{sub 3}) with a mixed rhombohedral and tetragonal structure have been quantified using full pattern Rietveld refinement of in situ high-energy x-ray diffraction data. The analysis methodology allows a quantification of all strain mechanisms for each phase in a morphotropic composition and is applicable to use in a wide variety of piezoelectric compositions. It is shown that during the poling of this material 24%, 44%, and 32% of the total macroscopic strain is generated from lattice strain, domain switching, and phase transformation strains, respectively. The resultsmore » also suggest that the tetragonal phase contributes the most to extrinsic domain switching strain, whereas the lattice strain primarily stems from the rhombohedral phase. The analysis also suggests that almost 32% of the total strain is lost or is a one-time effect due to the irreversible nature of the electric-field-induced phase transformation in the current composition. This information is relevant to on-going compositional development strategies to harness the electric-field-induced phase transformation strain of (Bi{sub 1/2}Na{sub 1/2})TiO{sub 3}-based lead-free piezoelectric materials for actuator applications.« less

Observation of multiple dielectric relaxations in BaTiO3-Bi(Li1/3Ti2/3)O3 ceramics

NASA Astrophysics Data System (ADS)

Zhou, Changrong; Feteira, Antonio

2017-11-01

Dense (1 - x)BaTiO3- xBi(Li1/3Ti2/3)O3 ceramics were fabricated by the solid state reaction route. Powder X-ray diffraction analyses revealed an increase in the unit cell volume with increasing x and a change on the average crystal structure from tetragonal (space group P4mm) to cubic ( Pm\\bar{3}m ) at x > 0.10. Raman spectroscopy analyses corroborated a change of symmetry, but also showed the local structure for x > 0.10 to be inconsistent with the centrosymmetric ( Pm\\bar{3}m ) space group. The dielectric measurements revealed for the first time, to our knowledge, a double relaxor behaviour in a BaTiO3-based solid solution. Basically, with increasing x, the sharp ferroelectric anomaly at the Curie temperature ( T c) shifts towards lower temperatures until a relaxor-type response is observed, but simultaneously, another relaxation emerges above T c. The first arises from poor coupling between polar nanoregions, whereas the later obeys the Arrhenius Law and may be associated either with a defect-dipole reorientation or a Skanavi-type mechanism.

Spin-Orbit Relaxation Rates of Bi(6p(3) 2D(3/2)) Following Photolysis of Bi(CH3)3 at Lambda = 193 nm

DTIC Science & Technology

1989-07-07

C. E. Gardner, J. Chem. Phys. 80, 1861 and references therein (1981). 12. R. F. Heidner III, H . Helvajian , J. S. Holloway, and J. B. Koffend (to be...observed from the blue BiF(A - X) band system. [1 0] NF(aIA) is conveniently produced by means of the H2/NF2 chain reac- tion[111 F + H2 * HF(v) + H (3... H + NF2 NF(a 1) + F (4) in which reaction 4 produces the (a 1A) state with a branching ratio of >0.9. [7,121 Thus, we have a system capable of

Nd3+-doped TeO2-Bi2O3-ZnO transparent glass ceramics for laser application at 1.06 μm

NASA Astrophysics Data System (ADS)

Hu, Xiaolin; Luo, Zhiwei; Liu, Taoyong; Lu, Anxian

2017-04-01

The high crystallinity transparent glass ceramics based on Nd3+-doped 70TeO2-15Bi2O3-15ZnO (TBZ) compositions were successfully prepared by two-step heat treatment process. The effects of Nd2O3 content on the thermal, structural, mechanical, and optical properties of TBZ glass ceramics were studied. The incorporation of Nd2O3 enhanced the crystallization tendency in the matrix glass composition. The crystal phase and morphology of Bi2Te4O11 in the glass ceramics were confirmed by X-ray diffraction and field emission scanning electron microscopy. Due to precipitate more crystal phase, the hardness values increased from 3.21 to 3.66 GPa. Eight absorption peaks were observed from 400 to 900 nm and three emission bands appeared in the range of 850-1400 nm. With the increasing of Nd2O3 content from 0.5 to 2.5 wt%, the intensity of absorption peaks enhanced and the emission intensity increased up to 1.0 wt% and then fell down for further dopant concentration. The fluorescence decay lifetime decreased rapidly starting from 1.5 wt% Nd2O3 content due to the obvious energy migration among Nd3+. According to the extreme strong emission band around 1062 nm and the optimum Nd2O3 content (1.0 wt%), N10 glass ceramic was considered as a potential material for 1.06 μm laser applications.

Magnetotransport study of (Sb 1-xBi x) 2Te 3 thin films on mica substrate for ideal topological insulator

DOE PAGES

Ni, Yan; Zhang, Zhen; Nlebedim, Cajetan I.; ...

2016-02-29

In this study, we deposited high quality (Sb 1–xBi x) 2Te 3 on mica substrate by molecular beam epitaxy and investigated their magnetotransport properties. It is found that the average surface roughness of thin films is lower than 2 nm. Moreover, a local maxima on the sheet resistance is obtained with x = 0.043, indicating a minimization of bulk conductivity at this composition. For (Sb 0.957Bi 0.043) 2Te 3, weak antilocalization with coefficient of -0.43 is observed, confirming the existence of 2D surface states. Moreover Shubnikov-de Hass oscillation behavior occurs under high magnetic field. The 2D carrier density is thenmore » determined as 0.81 × 10 16 m –2, which is lower than that of most TIs reported previously, indicating that (Sb 0.957Bi 0.043) 2Te 3 is close to ideal TI composition of which the Dirac point and Fermi surface cross within the bulk bandgap. Our results thus demonstrate the best estimated composition for ideal TI is close to (Sb 0.957Bi 0.043) 2Te 3 and will be helpful for designing TI-based devices.« less

Enhancement in superconducting properties of Bi2Sr2Ca1Cu2O8+θ (Bi-2212) by means of boron oxide additive

NASA Astrophysics Data System (ADS)

Fallah-Arani, Hesam; Baghshahi, Saeid; Sedghi, Arman; Stornaiuolo, Daniela; Tafuri, Francesco; Riahi-Noori, Nastaran

2018-05-01

By using a solid state method, Bi2Sr2Ca1Cu2O8+θ (Bi-2212) polycrystalline samples were synthesized with the addition of boron oxide additive, with the aim of improving the performance of this compound for large scale applications. As the first step, the parameters for the solid state method, in particular sintering temperature, were optimized in order to obtain pure Bi-2212 samples with an optimal microstructure. Then, based on this optimization, the properties of the Bi2Sr2Ca1Cu2BxOy samples with x = 0.05, 0.1, and 0.2 were studied using several characterization techniques. It was found that the sample having x = 0.05 showed a magnetic hysteresis loop larger than that of the pure Bi-2212 sample and a critical current density value of 3.71 × 105 A/cm2, comparable to the best results found in the literature for Bi-2212, while preserving well-stacked and oriented grains.

Temperature-induced local and average structural changes in BaTiO3-xBi(Zn1/2Ti1/2)O3 solid solutions: The origin of high temperature dielectric permittivity

NASA Astrophysics Data System (ADS)

Hou, Dong; Usher, Tedi-Marie; Zhou, Hanhan; Raengthon, Natthaphon; Triamnak, Narit; Cann, David P.; Forrester, Jennifer S.; Jones, Jacob L.

2017-08-01

The existence of local tetragonal distortions is evidenced in the BaTiO3-xBi(Zn1/2Ti1/2)O3 (BT-xBZT) relaxor dielectric material system at elevated temperatures. The local and average structures of BT-xBZT with different compositions are characterized using in situ high temperature total scattering techniques. Using the box-car fitting method, it is inferred that there are tetragonal polar clusters embedded in a non-polar pseudocubic matrix for BT-xBZT relaxors. The diameter of these polar clusters is estimated as 2-3 nm at room temperature. Sequential temperature series fitting shows the persistence of the tetragonal distortion on the local scale, while the average structure transforms to a pseudocubic paraelectric phase at high temperatures. The fundamental origin of the temperature stable permittivity of BT-xBZT and the relationship with the unique local scale structures are discussed. This systematic structural study of the BT-xBZT system provides both insight into the nature of lead-free perovskite relaxors, and advances the development of a wide range of electronics with reliable high temperature performance.

Temperature-induced local and average structural changes in BaTiO 3- xBi(Zn 1/2Ti 1/2)O 3 solid solutions: The origin of high temperature dielectric permittivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hou, Dong; Usher, Tedi -Marie; Zhou, Hanhan

The existence of local tetragonal distortions is evidenced in the BaTiO 3–xBi(Zn 1/2Ti 1/2)O 3 (BT–xBZT) relaxor dielectric material system at elevated temperatures. The local and average structures of BT-xBZT with different compositions are characterized using in situ high temperature total scattering techniques. Using the box-car fitting method, it is inferred that there are tetragonal polar clusters embedded in a non-polar pseudocubic matrix for BT-xBZT relaxors. The diameter of these polar clusters is estimated as 2–3 nm at room temperature. Sequential temperature series fitting shows the persistence of the tetragonal distortion on the local scale, while the average structure transformsmore » to a pseudocubic paraelectric phase at high temperatures. The fundamental origin of the temperature stable permittivity of BT-xBZT and the relationship with the unique local scale structures are discussed. This systematic structural study of the BT-xBZT system provides both insight into the nature of lead-free perovskite relaxors, and advances the development of a wide range of electronics with reliable high temperature performance.« less

Temperature-induced local and average structural changes in BaTiO 3- xBi(Zn 1/2Ti 1/2)O 3 solid solutions: The origin of high temperature dielectric permittivity

DOE PAGES

Hou, Dong; Usher, Tedi -Marie; Zhou, Hanhan; ...

2017-08-11

The existence of local tetragonal distortions is evidenced in the BaTiO 3–xBi(Zn 1/2Ti 1/2)O 3 (BT–xBZT) relaxor dielectric material system at elevated temperatures. The local and average structures of BT-xBZT with different compositions are characterized using in situ high temperature total scattering techniques. Using the box-car fitting method, it is inferred that there are tetragonal polar clusters embedded in a non-polar pseudocubic matrix for BT-xBZT relaxors. The diameter of these polar clusters is estimated as 2–3 nm at room temperature. Sequential temperature series fitting shows the persistence of the tetragonal distortion on the local scale, while the average structure transformsmore » to a pseudocubic paraelectric phase at high temperatures. The fundamental origin of the temperature stable permittivity of BT-xBZT and the relationship with the unique local scale structures are discussed. This systematic structural study of the BT-xBZT system provides both insight into the nature of lead-free perovskite relaxors, and advances the development of a wide range of electronics with reliable high temperature performance.« less

Magnetic quantum phase transition in Cr-doped Bi2(SexTe1-x)3 driven by the Stark effect

NASA Astrophysics Data System (ADS)

Zhang, Zuocheng; Feng, Xiao; Wang, Jing; Lian, Biao; Zhang, Jinsong; Chang, Cuizu; Guo, Minghua; Ou, Yunbo; Feng, Yang; Zhang, Shou-Cheng; He, Ke; Ma, Xucun; Xue, Qi-Kun; Wang, Yayu

2017-10-01

The recent experimental observation of the quantum anomalous Hall effect has cast significant attention on magnetic topological insulators. In these magnetic counterparts of conventional topological insulators such as Bi2Te3, a long-range ferromagnetic state can be established by chemical doping with transition-metal elements. However, a much richer electronic phase diagram can emerge and, in the specific case of Cr-doped Bi2(SexTe1-x)3, a magnetic quantum phase transition tuned by the actual chemical composition has been reported. From an application-oriented perspective, the relevance of these results hinges on the possibility to manipulate magnetism and electronic band topology by external perturbations such as an electric field generated by gate electrodes—similar to what has been achieved in conventional diluted magnetic semiconductors. Here, we investigate the magneto-transport properties of Cr-doped Bi2(SexTe1-x)3 with different compositions under the effect of a gate voltage. The electric field has a negligible effect on magnetic order for all investigated compositions, with the remarkable exception of the sample close to the topological quantum critical point, where the gate voltage reversibly drives a ferromagnetic-to-paramagnetic phase transition. Theoretical calculations show that a perpendicular electric field causes a shift in the electronic energy levels due to the Stark effect, which induces a topological quantum phase transition and, in turn, a magnetic phase transition.

The electronic structure of Bi 2.0Sr 1.8La 0.3Ca 0.8Cu 2.1O 8+δ superconductors studied using ultraviolet and X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Lindberg, P. A. P.; Shen, Z.-X.; Dessau, D. S.; Wells, B. O.; Borg, A.; Ellis, W.; Mitzi, D. B.; Lindau, I.; Spicer, W. E.; Kapitulnik, A.

1989-07-01

Photoemission measurements on single crystals of La-doped 2212 (Bi 2.0Sr 1.8La 0.3Ca 0.8Cu 2.1O 8+δ) superconductors were carried out utilizing both synchrotron and Al K α (1486.6 eV) radiation. A quantitative analysis of the photoemission data in comparison with similar data for the undoped 2212 material indicates that the La atoms preferentially occupy the Sr sites in the SrO layer next to the BiO plane. Evidence of alternation of the electronic environment of the Bi atoms is found in the Bi 5d core level spectra which show a shoulder at ≈ 1.2 eV higher binding energy, presumably due to the partial substitution of trivalent La ions (La 3+) for divalent Sr ions (Sr 2+). As for the undoped 2212 material, the photoemission spectra reveal a clear Fermi level cut-off at room temperature, single component O ls core level emission, and a Cu 2p satellite to main line intensity ratio of 0.4.

Photoreduction of Carbon Dioxide to Methane Over Sb1.5Sn8.5-x Ti x O19.0 with High Conductivity.

PubMed

Do, Jeong Yeon; Kwak, Byeong Sub; Kang, Misook

2018-09-01

In order to enhance the photoreduction of CO2 to CH4, a new type of photocatalyst, Sb1.5Sn8.5-xTixO19.0, with high conductivity and low bandgap was developed by partially incorporating Ti into the framework of Sb1.5Sn8.5O19.0 (antimony-doped tin oxide, ATO) using a controlled hydrothermal method. XRD and TEM analyses indicated that the Sb1.5Sn8.5-xTixO19.0 particles exhibited a tetragonal crystal structure and were approximately 20 nm in size. Furthermore, the bandgap and conductivity of these materials increased with increasing Ti content. A study of the photoreduction of CO2 with H2O revealed a remarkable increase in the generation of CH4 over the Sb1.5Sn8.5-xTixO19.0 catalysts. In particular, CH4 generation was the highest when Sb1.5Sn8.5Ti1.0O19.0 was used as the photocatalyst, and was three-fold higher than that achieved by using anatase TiO2. Photoluminescence studies showed that the enhanced photocatalytic activity of the Sb1.5Sn8.5-xTixO19.0 materials could be attributed to the interfacial transfer of photogenerated charges, which led to an effective charge separation and inhibition of the recombination of photogenerated electron-hole (e-/h+) pairs.

Synthesis and crystal structures of new oxyapatites BiCa{sub 4-x}La{sub x}(VO{sub 4}){sub 3-x}(GeO{sub 4}){sub x}O, x=1-3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhuravlev, V.D., E-mail: zhvd@ihim.uran.ru; Tyutyunnik, A.P.; Zubkov, V.G.

2012-10-15

New germanate-vanadates with the general formula BiCa{sub 4-x}La{sub x}(VO{sub 4}){sub 3-x}(GeO{sub 4}){sub x}O, x=1-3, have been synthesized by the nitrate-citrate method and characterized. Structural refinement based on X-ray powder diffraction data showed that these compounds are isostructural with BiCa{sub 4}(VO{sub 4}){sub 3}O (space group P6{sub 3}/m (N 176), Z=2, a=9.8327-9.8755(3), and c=7.1203-7.2133(2) ). They may be viewed as continuous series of solid solutions where Ca{sup 2+} and V{sup 5+} cations in the crystal lattice of vanadate BiCa{sub 4}(VO{sub 4}){sub 3}O are replaced by La{sup 3+} and Ge{sup 4+} cations. In the process of substitution, the La{sup 3+} cations occupy mainlymore » the 4f lattice sites of the germanate-vanadate oxyapatites, but the filling of the 4f and 6h lattice sites in the germanate BiCaLa{sub 3}(GeO{sub 4}){sub 3} is equivalent. IR and Raman spectra were studied. The Raman spectra clearly show a two-mode behavior: the lines of GeO{sub 4} and VO{sub 4} are separated from each other, and the (V/Ge)O{sub 4} tetrahedra exhibit a quasi-independent behavior. - Graphical abstract: Schematic drawing of the BiCa{sub 3}La(VO{sub 4}){sub 2}(GeO{sub 4})O structure in projection on the ac plane. Green-V and Ge, red-Ca(1) and La(1), yellow-Ca(2), La(2) and Bi, dark-blue-O(1)-O(4), blue-O(5). Highlights: Black-Right-Pointing-Pointer The citrate synthesis of germanate-vanadate oxyapatites. Black-Right-Pointing-Pointer The synthesized compounds crystallize in the hexagonal symmetry. Black-Right-Pointing-Pointer A single series of solid solutions BiCa{sub 4-x}La{sub x}(VO{sub 4}){sub 3-x}(GeO{sub 4}){sub x}O, (x=0-3). Black-Right-Pointing-Pointer IR an Raman spectra of mixed crystals.« less

Phase transitions and magnetoelectric coupling in BiFe1-xZnxO3 multiferroics

NASA Astrophysics Data System (ADS)

Amirov, Abdulkarim A.; Chaudhari, Yogesh A.; Bendre, Subhash T.; Chichay, Ksenia A.; Rodionova, Valeria V.; Yusupov, Dibir M.; Omarov, Zairbek M.

2018-04-01

Multiferroic BiFe1-xZnxO3 ceramics were prepared by solution combustion method. Their structure, magnetoelectric, dielectric, magnetic, thermal characteristics were studied. The magnetic M(T) and heat capacity Cp(T) measurements demonstrate an antiferromagnetic to paramagnetic phase transition (TN) around 635 K. The anomaly on the temperature dependence of the dielectric constant near TN was observed, which could be induced by the magnetoelectric coupling between electric and magnetic ordering. The magnetoelectric behavior was also confirmed by the linear relation between Δɛ and M2, which is in the agreement of the Ginzburg-Landau theory for the second-order phase transition.

Oxygen vacancies induced switchable and nonswitchable photovoltaic effects in Ag/Bi{sub 0.9}La{sub 0.1}FeO{sub 3} /La{sub 0.7}Sr{sub 0.3}MnO{sub 3} sandwiched capacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, R. L., E-mail: gaorongli2008@163.com, E-mail: jrsun@iphy.ac.cn; Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Science, Beijing 100190; Yang, H. W.

2014-01-20

The short circuit photocurrent (I{sub sc}) was found to be strongly dependent on the oxygen vacancies (V{sub Os}) distribution in Ag/Bi{sub 0.9}La{sub 0.1}FeO{sub 3}/La{sub 0.7}Sr{sub 0.3}MnO{sub 3} heterostructures. In order to manipulate the V{sub Os} accumulated at either the Ag/Bi{sub 0.9}La{sub 0.1}FeO{sub 3} or the Bi{sub 0.9}La{sub 0.1}FeO{sub 3}/La{sub 0.7}Sr{sub 0.3}MnO{sub 3} interface by pulse voltages, switchable or nonswitchable photocurrent can be observed without or with changing the polarization direction. The sign of photocurrent could be independent of the direction of polarization when the variation of diffusion current and the modulation of the Schottky barrier at the Ag/Bi{sub 0.9}La{sub 0.1}FeO{submore » 3} interface induced by oxygen vacancies are large enough to offset those induced by polarization. Our work provides deep insights into the nature of photovoltaic effects in ferroelectric films, and will facilitate the advanced design of switchable devices combining spintronic, electronic, and optical functionalities.« less

Local and average structures of BaTiO 3-Bi(Zn 1/2Ti 1/2)O 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Usher, Tedi-Marie; Iamsasri, Thanakorn; Forrester, Jennifer S.

The complex crystallographic structures of (1-x)BaTiO 3-xBi(Zn 1/2Ti 1/2)O 3 (BT-xBZT) are examined using high resolution synchrotron X-ray diffraction, neutron diffraction, and neutron pair distribution function (PDF) analyses. The short-range structures are characterized from the PDFs, and a combined analysis of the X-ray and neutron diffraction patterns is used to determine the long-range structures. Our results demonstrate that the structure appears different when averaged over different length scales. In all compositions, the local structures determined from the PDFs show local tetragonal distortions (i.e., c/a > 1). But, a box-car fitting analysis of the PDFs reveals variations at different length scales.more » For 0.80BT-0.20BZT and 0.90BT-0.10BZT, the tetragonal distortions decrease at longer atom-atom distances (e.g., 30 vs. 5 ). When the longest distances are evaluated (r > 40 ), the lattice parameters approach cubic. Neutron and X-ray diffraction yield further information about the long-range structure. Compositions 0.80BT-0.20BZT and 0.90BT-0.10BZT appear cubic by Bragg diffraction (no peak splitting), consistent with the PDFs at long distances. However, these patterns cannot be adequately fit using a cubic lattice model; modeling their structures with the P4mm space group allows for a better fit to the patterns because the space group allows for c-axis atomic displacements that occur at the local scale. Furthermore, for the compositions 0.92BT-0.08BZT and 0.94BT-0.06BZT, strong tetragonal distortions are observed at the local scale and a less-distorted tetragonal structure is observed at longer length scales. In Rietveld refinements, the latter is modeled using a tetragonal phase. Since the peak overlap in these two-phase compositions limits the ability to model the local-scale structures as tetragonal, it is approximated in the refinements as a cubic phase. These results demonstrate that alloying BT with BZT results in increased disorder and

Local and average structures of BaTiO 3-Bi(Zn 1/2Ti 1/2)O 3

DOE PAGES

Usher, Tedi-Marie; Iamsasri, Thanakorn; Forrester, Jennifer S.; ...

2016-11-11

The complex crystallographic structures of (1-x)BaTiO 3-xBi(Zn 1/2Ti 1/2)O 3 (BT-xBZT) are examined using high resolution synchrotron X-ray diffraction, neutron diffraction, and neutron pair distribution function (PDF) analyses. The short-range structures are characterized from the PDFs, and a combined analysis of the X-ray and neutron diffraction patterns is used to determine the long-range structures. Our results demonstrate that the structure appears different when averaged over different length scales. In all compositions, the local structures determined from the PDFs show local tetragonal distortions (i.e., c/a > 1). But, a box-car fitting analysis of the PDFs reveals variations at different length scales.more » For 0.80BT-0.20BZT and 0.90BT-0.10BZT, the tetragonal distortions decrease at longer atom-atom distances (e.g., 30 vs. 5 ). When the longest distances are evaluated (r > 40 ), the lattice parameters approach cubic. Neutron and X-ray diffraction yield further information about the long-range structure. Compositions 0.80BT-0.20BZT and 0.90BT-0.10BZT appear cubic by Bragg diffraction (no peak splitting), consistent with the PDFs at long distances. However, these patterns cannot be adequately fit using a cubic lattice model; modeling their structures with the P4mm space group allows for a better fit to the patterns because the space group allows for c-axis atomic displacements that occur at the local scale. Furthermore, for the compositions 0.92BT-0.08BZT and 0.94BT-0.06BZT, strong tetragonal distortions are observed at the local scale and a less-distorted tetragonal structure is observed at longer length scales. In Rietveld refinements, the latter is modeled using a tetragonal phase. Since the peak overlap in these two-phase compositions limits the ability to model the local-scale structures as tetragonal, it is approximated in the refinements as a cubic phase. These results demonstrate that alloying BT with BZT results in increased disorder and

Room-Temperature Multiferroics and Thermal Conductivity of 0.85BiFe1-2xTixMgxO3-0.15CaTiO3 Epitaxial Thin Films (x = 0.1 and 0.2).

PubMed

Zhang, Ji; Sun, Wei; Zhao, Jiangtao; Sun, Lei; Li, Lei; Yan, Xue-Jun; Wang, Ke; Gu, Zheng-Bin; Luo, Zhen-Lin; Chen, Yanbin; Yuan, Guo-Liang; Lu, Ming-Hui; Zhang, Shan-Tao

2017-08-02

Thin films of 0.85BiFe 1-2x Ti x Mg x O 3 -0.15CaTiO 3 (x = 0.1 and 0.2, abbreviated to C-1 and C-2, respectively) have been fabricated on (001) SrTiO 3 substrate with and without a conductive La 0.7 Sr 0.3 MnO 3 buffer layer. The X-ray θ-2θ and ϕ scans, atomic force microscopy, and cross-sectional transmission electron microscopy confirm the (001) epitaxial nature of the thin films with very high growth quality. Both the C-1 and C-2 thin films show well-shaped magnetization-magnetic field hysteresis at room temperature, with enhanced switchable magnetization values of 145.3 and 42.5 emu/cm 3 , respectively. The polarization-electric loops and piezoresponse force microscopy measurements confirm the room-temperature ferroelectric nature of both films. However, the C-1 films illustrate a relatively weak ferroelectric behavior and the poled states are easy to relax, whereas the C-2 films show a relatively better ferroelectric behavior with stable poled states. More interestingly, the room-temperature thermal conductivity of C-1 and C-2 films are measured to be 1.10 and 0.77 W/(m·K), respectively. These self-consistent multiferroic properties and thermal conductivities are discussed by considering the composition-dependent content and migration of Fe-induced electrons and/or charged point defects. This study not only provides multifunctional materials with excellent room-temperature magnetic, ferroelectric, and thermal conductivity properties but may also stimulate further work to develop BiFeO 3 -based materials with unusual multifunctional properties.

CERES BiDirectional Scans (BDS) data in HDF (CER_BDS_Aqua-FM3_Edition1)

NASA Technical Reports Server (NTRS)

Wielicki, Bruce A. (Principal Investigator)

Each BiDirectional Scans (BDS) data product contains twenty-four hours of Level-1b data for each CERES scanner instrument mounted on each spacecraft. The BDS includes samples taken in normal and short Earth scan elevation profiles in both fixed and rotating azimuth scan modes (including space, internal calibration, and solar calibration views). The BDS contains Level-0 raw (unconverted) science and instrument data as well as the geolocated converted science and instrument data. The BDS contains additional data not found in the Level-0 input file, including converted satellite position and velocity data, celestial data, converted digital status data, and parameters used in the radiance count conversion equations. The following CERES BDS data sets are currently available: CER_BDS_TRMM-PFM_Edition1 CER_BDS_Terra-FM1_Edition1 CER_BDS_Terra-FM2_Edition1 CER_BDS_Terra-FM1_Edition2 CER_BDS_Terra-FM2_Edition2 CER_BDS_Aqua-FM3_Edition1 CER_BDS_Aqua-FM4_Edition1 CER_BDS_Aqua-FM3_Edition2 CER_BDS_Aqua-FM4_Edition2 CER_BDS_Aqua-FM3_Edition1-CV CER_BDS_Aqua-FM4_Edition1-CV CER_BDS_Terra-FM1_Edition1-CV CER_BDS_Terra-FM2_Edition1-CV. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1997-12-27; Stop_Date=2005-11-02] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180] [Data_Resolution: Temporal_Resolution=1 day; Temporal_Resolution_Range=Daily - < Weekly].

The series Bi2Sr2Ca(n-1) Cu(n)O(2n+4) (1 less than or equal to n less than or equal to 5): Phase stability and superconducting properties

NASA Technical Reports Server (NTRS)

Deguire, Mark R.; Bansal, Narottam P.; Farrell, David E.; Finan, Valerie; Kim, Cheol J.; Hills, Bethanie J.; Allen, Christopher J.

1989-01-01

Phase relations at 850 and 870 C, melting transitions in air, oxygen, and helium were studied for Bi(2.1)Sr(1.9) CuO6 and for the Bi2Sr2Ca(n-1) Cu(n)O(2n+4) for n = 1, 2, 3, 4, 5, and infinity (CaCuO2). Up to 870 C, the n = 2 composition resides in the compatibility tetrahedron bounded by Bi(2+x)(Sr,Ca)(3-y) Cu2O8, (Sr,Ca)14 Cu24O41, Ca2CuO3, and a Bi-Sr-Ca-O phase. The n is greater than or equal to 3 compositions reside in the compatibility tetrahedron Bi(2+x)(Sr,Ca)(3-y) Cu2O8 - (Sr,Ca)14 Cu24O41 - Ca2CuO3 - CuO up to 850 C. However, Bi(2+x)Sr(4-y) Cu3O10 forms for n is greater than or equal to 3 after extended heating at 870 C. Bi(2+x)Sr(2-y) CuO6 and Bi(2+x)(Sr,Ca)(3-y) Cu2O8 melt in air at 914 C and 895 C respectively. During melting, all of the compositions studied lose 1 to 2 percent by weight of oxygen from the reduction of copper. Bi(2+x)Sr(2-y) CuO6, Bi(2+n)(Sr,Ca)(3-y) Cu2O8, and Bi(2+x)(Sr,Ca)(4-y) Cu3O10 exhibit crystallographic alignment in a magnetic field, with the c-axes orienting parallel to the field.

Giant piezoelectric property of (110) oriented BaxSr1-xTiO3 films

NASA Astrophysics Data System (ADS)

Chen, Z. H.; Chen, Z.; Qiu, J. H.; Yuan, N. Y.; Ding, J. N.

2017-10-01

A phenomenological Landau-Devonshire theory is applied to investigate the phase diagrams and physical properties of (110) oriented BaxSr1-xTiO3 films. New ferroelectric phases, such as the tetragonal a1 phase and the orthorhombic a2 c phase, appear in the ;misfit strain-temperature; phase diagrams for (110) oriented films compared with that of (001) oriented films. Moreover, the orthorhombic a2 c phase, and the tetragonal c phase and the triclinic γ phase are stable at low temperature for x = 0.5 and x = 0.7 , respectively. The ferroelectric, dielectric, and piezoelectric properties strongly depend on the misfit strain and electric field. (110) oriented Ba0.7Sr0.3TiO3 film has the larger ferroelectric polarization and piezoelectric coefficient than that of Ba0.5Sr0.5TiO3 film. The giant piezoelectric coefficient of 340 pm / V is obtained at the electric field of 50 KV / cm in (110) oriented Ba0.7Sr0.3TiO3 film, which is comparable with the values of Pb (Zr1-xTix)O3 and (1 - x) Pb (Mg1/3Nb2/3)O3 -xPbTiO3 films. It makes (110) oriented BaxSr1-xTiO3 films suitable for applications in electromechanical devices.

Influence of Element Substitution on Corrosion Behavior of Bi2Te3-Based Compounds

NASA Astrophysics Data System (ADS)

Kohri, Hitoshi; Yagasaki, Takayoshi

2018-02-01

Atmospheric water may condense on the surface of Bi2Te3-based compounds constituting the Peltier module, depending on the operating environment used. In the stage of disposal, Bi2Te3-based compounds may come into contact with water in waste disposal sites. There are very few publications about the influence of condensed water on Peltier modules. Bi2Te3-Sb2Te3 or Bi2Te3-Bi2Se3 pseudo binary system compounds are used as p-type material or n-type material, respectively. The lattice distortion will be induced in the crystal of Bi2Te3-based compounds by element substitution due to the reduction in their thermal conductivity. However, the influence of element substitution on the corrosion behavior of Bi2Te3-based compounds remains unclear. In this study, the influence of element substitution on the corrosion behavior of Bi2Te3-based compounds with practical compositions has been investigated. Bi0.5Sb1.5Te3 or Bi2Te2.85Se0.15 was prepared by the vertical Bridgman method. The electrochemical properties at room temperature were evaluated by cyclic voltammetry in a standard three-electrode cell. The working electrolyte was a naturally aerated 0.6 or 3.0 mass% NaCl solution. From the tendency for corrosion potential for all the samples, the corrosion sensitivity of ternary compounds was slightly higher than that of binary compounds. From the trend of current density, it was found that Bi0.5Sb1.5Te3 had a corrosion resistance intermediate between Bi2Te3 and Sb2Te3. On the other hand, corrosion resistance was affected despite a small amount of Se substitution, and the corrosion resistance of Bi2Te2.85Se0.15 was close to or lower than that of Bi2Se3. From the observation results of the corrosion products, the trends of morphology and composition of corrosion products for Bi0.5Sb1.5Te3 or Bi2Te2.85Se0.15 were consistent with those of Sb2Te3 or Bi2Se3, respectively. From the results of x-ray photoelectron spectroscopy for the electrolyte after testing, the possibility that a

Influence of Element Substitution on Corrosion Behavior of Bi2Te3-Based Compounds

NASA Astrophysics Data System (ADS)

Kohri, Hitoshi; Yagasaki, Takayoshi

2018-06-01

Atmospheric water may condense on the surface of Bi2Te3-based compounds constituting the Peltier module, depending on the operating environment used. In the stage of disposal, Bi2Te3-based compounds may come into contact with water in waste disposal sites. There are very few publications about the influence of condensed water on Peltier modules. Bi2Te3-Sb2Te3 or Bi2Te3-Bi2Se3 pseudo binary system compounds are used as p-type material or n-type material, respectively. The lattice distortion will be induced in the crystal of Bi2Te3-based compounds by element substitution due to the reduction in their thermal conductivity. However, the influence of element substitution on the corrosion behavior of Bi2Te3-based compounds remains unclear. In this study, the influence of element substitution on the corrosion behavior of Bi2Te3-based compounds with practical compositions has been investigated. Bi0.5Sb1.5Te3 or Bi2Te2.85Se0.15 was prepared by the vertical Bridgman method. The electrochemical properties at room temperature were evaluated by cyclic voltammetry in a standard three-electrode cell. The working electrolyte was a naturally aerated 0.6 or 3.0 mass% NaCl solution. From the tendency for corrosion potential for all the samples, the corrosion sensitivity of ternary compounds was slightly higher than that of binary compounds. From the trend of current density, it was found that Bi0.5Sb1.5Te3 had a corrosion resistance intermediate between Bi2Te3 and Sb2Te3. On the other hand, corrosion resistance was affected despite a small amount of Se substitution, and the corrosion resistance of Bi2Te2.85Se0.15 was close to or lower than that of Bi2Se3. From the observation results of the corrosion products, the trends of morphology and composition of corrosion products for Bi0.5Sb1.5Te3 or Bi2Te2.85Se0.15 were consistent with those of Sb2Te3 or Bi2Se3, respectively. From the results of x-ray photoelectron spectroscopy for the electrolyte after testing, the possibility that a

Structural and morphological studies on Bi{sub 1-x}Ca{sub x}MnO{sub 3} thin films grown by RF magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pugazhvadivu, K. S.; Santhiya, M.; Tamilarasan, K., E-mail: dr.k.tamilarasan@gmail.com

2016-05-23

Bi{sub 1-x}Ca{sub x}MnO{sub 3} (0 ≤ X ≤ 0.4) thin films are deposited on n–type Si (100) substrate at 800 °C by RF magnetron sputtering. X-ray diffraction pattern shows that the films are crystallized in monoclinic structure with C2 space group. The crystallite size and induced strain in the prepared films are measured by W-H plot. The cell parameters and texture coefficient of the films are calculated. The surface morphology of the films is examined by atomic force microscope. The study confirms the optimum level of calcium doping is 20 at. % in Bi site of BiMnO{sub 3} film, thesemore » findings pave the way for further research in the Ca modified BiMnO{sub 3} films towards device fabrication.« less

Morphology effect on photocatalytic activity in Bi3Fe0.5Nb1.5O9.

PubMed

Yin, Xiaofeng; Li, Xiaoning; Gu, Wen; Zou, Wei; Liu, Huan; Zhu, Liuyang; Fu, Zhengping; Lu, Yalin

2018-06-29

In this work, the Aurivillius-phase ferroelectric Bi 3 Fe 0.5 Nb 1.5 O 9 were synthesized by hydrothermal (BFNO-H) and solid state methods (BFNO-S), respectively. The BFNO-H shows a hierarchical morphology, which is stacked by intersecting single-crystal nanosheets with {001} and {110} exposed facets, while the BFNO-S shows disorganized micron-scale morphology. BFNO-H shows a much stronger photodegradation activity (10.4 times and 9.8 times) than BFNO-S in the visible-light photodegradation of rhodamine B (RhB) and salicylic acid. The higher photodegradation activity of BFNO-H was firstly ascribed to the hierarchical structure and the larger specific surface area (16.586 m 2 g -1 ) because a large specific surface area can increase reactive sites and shorten photogenerated carrier migration distance. However, after being normalized by the specific surface area, BFNO-H still performs better than BFNO-S, implying that the specific surface area is not the only factor that determines the photocatalytic activity. Considering that the built-in electric field originating from spontaneous polarization in Bi 3 Fe 0.5 Nb 1.5 O 9 has existed in both ab plane and c direction, it matches well with the {001} and {110} exposed facets of BFNO-H nanosheets. This appropriate matching in BFNO-H nanosheets may improve the separation and transmission of photogenerated electron-hole pairs and further enhance its photocatalytic activity. Moreover, the trapping experiments reveals that holes (h + ) are the main active species and hole-derived oxidation is the main redox reaction during photodegradation of organic pollutions.

Morphology effect on photocatalytic activity in Bi3Fe0.5Nb1.5O9

NASA Astrophysics Data System (ADS)

Yin, Xiaofeng; Li, Xiaoning; Gu, Wen; Zou, Wei; Liu, Huan; Zhu, Liuyang; Fu, Zhengping; Lu, Yalin

2018-06-01

In this work, the Aurivillius-phase ferroelectric Bi3Fe0.5Nb1.5O9 were synthesized by hydrothermal (BFNO-H) and solid state methods (BFNO-S), respectively. The BFNO-H shows a hierarchical morphology, which is stacked by intersecting single-crystal nanosheets with {001} and {110} exposed facets, while the BFNO-S shows disorganized micron-scale morphology. BFNO-H shows a much stronger photodegradation activity (10.4 times and 9.8 times) than BFNO-S in the visible-light photodegradation of rhodamine B (RhB) and salicylic acid. The higher photodegradation activity of BFNO-H was firstly ascribed to the hierarchical structure and the larger specific surface area (16.586 m2 g‑1) because a large specific surface area can increase reactive sites and shorten photogenerated carrier migration distance. However, after being normalized by the specific surface area, BFNO-H still performs better than BFNO-S, implying that the specific surface area is not the only factor that determines the photocatalytic activity. Considering that the built-in electric field originating from spontaneous polarization in Bi3Fe0.5Nb1.5O9 has existed in both ab plane and c direction, it matches well with the {001} and {110} exposed facets of BFNO-H nanosheets. This appropriate matching in BFNO-H nanosheets may improve the separation and transmission of photogenerated electron–hole pairs and further enhance its photocatalytic activity. Moreover, the trapping experiments reveals that holes (h +) are the main active species and hole-derived oxidation is the main redox reaction during photodegradation of organic pollutions.

Lanthanide Contraction Effect In Magnetic Thermoelectric Materials Of Rare Earth-doped Bi1.5Pb0.5Ca2Co2O8

NASA Astrophysics Data System (ADS)

Sutjahja, Inge Magdalena; Akbar, Taufik; Nugroho, Agung

2010-12-01

We report in this paper the result of synthesis and crystal structure characterization of magnetic thermoelectric materials of rare-earth-doped Bi1.5Pb0.5Ca2Co2O8, namely Bi1.5Pb0.5Ca1.9RE0.1Co2O8 (RE = La, Pr, Sm, Eu, Gd, Ho). Single phase samples have been prepared by solid state reaction process using precursors of Bi2O3, PbO, CaCO3, RE2O3, and Co3O4. The precursors were pulverized, calcinated, and sintered in air at various temperatures for several hours. Analysis of XRD data shows that Bi1.5Pb0.5Ca1.9RE0.1Co2O8 compound is a layered system consisting of an alternate stack of CoO2 layer and Bi2Sr2O4 block along the c-axis. The misfit structure along b-direction is revealed from the difference of the b-axis length belonging to two sublattices, namely hexagonal CdI2-type CoO2 layer and rock-salt (RS) NaCl-type Bi2Sr2O4 block, while they possess the common a- and c-axis lattice parameters and β angles. The overall crystal structure parameters (a, b, and c) increases with type of doping from La to Ho, namely by decreasing the ionic radii of rare-earth ion. We discuss this phenomenon in terms of the lanthanide contraction, an effect commonly found in the rare-earth compound, results from poor shielding of nuclear charge by 4f electrons. In addition, the values of b-lattice parameters in these rare-earth doped samples are almost the same with those belongs to undoped parent compound (Bi1.5Pb0.5Sr2Co2O8) and its related Y-doped (Bi1.5Pb0.5Ca1.9Y0.1Co2O8) samples, while the c-values reduced significantly in rare-earth doped samples, with opposite trend with those of variation of a-axis length. Morevover, the misfit degree in rare-earth doped compound is higher in compared to parent compound and Y-doped samples. We argue that these structural changes induced by rare-earth doping may provide information for the variation of electronic structure of Co-ions (Co3+ and Co4+), in particular their different spin states of low-spin, intermediate-spin, and high-spin. This, in

Synthesis and characterization of Bi{sub 1.56}Sb{sub 1.48}Co{sub 0.96}O{sub 7} pyrochlore sun-light-responsive photocatalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naceur, Benhadria, E-mail: nacer1974@yahoo.fr; Abdelkader, Elaziouti, E-mail: elaziouti_a@yahoo.com; Dr Moulay Tahar University, Saida

2016-02-15

Graphical abstract: Heterogeneous photo Fenton process with dye sensitized mechanism of RhB by Bi{sub 1.56}Sb{sub 1.48}Co{sub 0.96}O{sub 7} compound. - Highlights: • Bi{sub 1.56}Sb{sub 1.48}Co{sub 0.96}O{sub 7} (BSCO) catalyst was synthesized by improved solid state reaction method. • BSCO/H{sub 2}O{sub 2}/UVA and BSCO/H{sub 2}O{sub 2}/SL catalyst systems exhibit excellent photocatalytic activities for rhodamine B. • The photocatalytic degradation was preceded via heterogeneous photo Fenton mechanism process. • ·OH radicals are the main reactive species for the degradation of RhB. - Abstract: Novel nanostructure pyrochlore Bi{sub 1.56}Sb{sub 1.48}Co{sub 0.96}O{sub 7} was successfully synthesized via solid state reaction method in air. Themore » as-synthesized photocatalyst was characterized by X-ray diffraction, Scanning electron microscopy and UV–vis diffuse reflectance spectroscopy techniques. The results showed that the BSCO was crystallized with the pyrochlore-type structure, cubic crystal system and space group Fd3m. The average particle size and band gap for BSCO were D = 76.29 nm and E{sub g} = 1.50 eV respectively. Under the optimum conditions for discoloration of the dye: initial concentration of 20 mg L{sup −1} RhB, pH 7, 25 °C, 0.5 mL H{sub 2}O{sub 2} and BSCO/dye mass ration of 1 g L{sup −1}, 97.77 and 90.16% of RhB were removed with BSCO/H{sub 2}O{sub 2} photocatalytic system within 60 min of irradiation time under UVA- and SL irradiations respectively. Pseudo-second-order kinetic model gave the best fit, with highest correlation coefficients (R{sup 2} ≥ 0.99). On the base of these results, the mechanism of the enhancement of the discoloration efficiency was discussed. .« less

Biosurfactant assisted synthesis of Fe3O4@rhamnolipid@BiOBr and its behaviour in plasma discharge system

NASA Astrophysics Data System (ADS)

Wang, Li; Yu, Zebin; Hou, Yanping; Peng, Zhenbo; Zhang, Li; Meng, Zhengcheng; Li, Fengyuan; He, Jun; Huang, Junlin

2016-06-01

A novel Fe3O4@rhamnolipid@BiOBr (FRB) was synthesized via a modified precipitation method and applied in the plasma discharge system. Rhamnolipid was used as biosurfactant to modify Fe3O4 by interacting with Fe3O4 via its aliphatic chain. The results show that the prepared FRB magnetic photocatalyst exhibited excellent photocatalytic activity and Fenton reaction behavior in the plasma discharge system. Meanwhile, the addition of FRB could improve energy efficiency of defluorination by 21.29 mg kW-1 h-1.

Electron transport in stepped Bi2Se3 thin films

NASA Astrophysics Data System (ADS)

Bauer, S.; Bobisch, C. A.

2017-08-01

We analyse the electron transport in a 16 quintuple layer thick stepped Bi2Se3 film grown on Si(1 1 1) by means of scanning tunnelling potentiometry (STP) and multi-point probe measurements. Scanning tunnelling microscopy images reveal that the local structure of the Bi2Se3 film is dominated by terrace steps and domain boundaries. From a microscopic study on the nm scale by STP, we find a mostly linear gradient of the voltage on the Bi2Se3 terraces which is interrupted by voltage drops at the position of the domain boundaries. The voltage drops indicate that the domain boundaries are scatterers for the electron transport. Macroscopic resistance measurements (2PP and in-line 4PP measurement) on the µm scale support the microscopic results. An additional rotational square 4PP measurement shows an electrical anisotropy of the sheet conductance parallel and perpendicular to the Bi2Se3 steps of about 10%. This is a result of the anisotropic step distribution at the stepped Bi2Se3 surface while domain boundaries are distributed isotropically. The determined value of the conductivity of the Bi2Se3 steps of about 1000 S cm-1 verifies the value of an earlier STP study.

Local structural distortion and electrical transport properties of Bi(Ni1/2Ti1/2)O3 perovskite under high pressure.

PubMed

Zhu, Jinlong; Yang, Liuxiang; Wang, Hsiu-Wen; Zhang, Jianzhong; Yang, Wenge; Hong, Xinguo; Jin, Changqing; Zhao, Yusheng

2015-12-16

Perovskite-structure materials generally exhibit local structural distortions that are distinct from long-range, average crystal structure. The characterization of such distortion is critical to understanding the structural and physical properties of materials. In this work, we combined Pair Distribution Function (PDF) technique with Raman spectroscopy and electrical resistivity measurement to study Bi(Ni1/2Ti1/2)O3 perovskite under high pressure. PDF analysis reveals strong local structural distortion at ambient conditions. As pressure increases, the local structure distortions are substantially suppressed and eventually vanish around 4 GPa, leading to concurrent changes in the electronic band structure and anomalies in the electrical resistivity. Consistent with PDF analysis, Raman spectroscopy data suggest that the local structure changes to a higher ordered state at pressures above 4 GPa.

First principles study of the magnetic properties and charge transfer of Ni-doped BiFeO3

NASA Astrophysics Data System (ADS)

Sun, Yuan; Sun, Zhenghao; Wei, Ren; Huang, Yuxin; Wang, Lili; Leng, Jing; Xiang, Peng; Lan, Min

2018-03-01

We present a first-principles study of electronic structures and magnetic properties in Ni-doped BiFeO3 using the density functional theory + U methods. The BiNixFe1-xO3 (x = 0.125, 0.25, 0.5) multiferroic ceramics represent ferromagnetic properties due to the ferrimagnetic order in Ni-O-Fe, and the magnetic moment rises with increase in Ni doping concentration agreeing well with experimental results. Ni atoms prefer to occupy the diagonal positions in the quasi-plane Ni-O-Fe eight-membered ring. Charge transfer from Bi 6s state to Ni 3d state through O 2p orbital lead to the 2+ oxidation state of Ni, indicating high Néel temperatures of BiNixFe1-xO3, and the electronic state of the system can be described as Bi4+xBi3+1-xNi2+xFe3+1-xO3. The spin polarization of Bi 6s state and O 2p state near the Fermi level contributes to the total magnetic moment. A spin-polarized acceptor level of about 0.4 eV constituted by Bi 6s state and O 2p state is found, which is responsible for the increase in leakage current of Ni-doped BiFeO3.

Glass-derived superconducting ceramics with zero resistance at 107 K in the Bi(1.5)Pb(0.5)Sr2Ca2Cu3O(x) system

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Farrell, D. E.

1989-01-01

A melt of composition Bi(1.5)Pb(0.5)Sr2Ca2Cu3O(x) was fast quenched to form a glass. This was subsequently air annealed and the influence of annealing time and temperature on the formation of various crystalline phases was investigated. X-ray powder diffraction indicate that none of the resulting samples were single phase. However, for an annealing temperature of 840 C, the volume fraction of the high Tc phase (isostructural with Bi2Sr2Ca2Cu3O10) increased with annealing time. A specimen annealed at this temperature for 243 h followed by slow cooling showed a sharp transition and Tc (R = 0) = 107.2 K.

Superconductivity in the 2-Dimensional Homologous Series AMm Bi3 Q5+m (m=1, 2) (A=Rb, Cs; M=Pb, Sn; Q=Se, Te).

PubMed

Malliakas, Christos D; Chung, Duck Young; Claus, Helmut; Kanatzidis, Mercouri G

2018-05-17

Superconductivity in the two-dimensional AM m Bi 3 Q 5+m family of semimetals is reported. The AMBi 3 Te 6 (m=1) and AM 2 Bi 3 Te 7 (m=2) members of the homologous series with A=Rb, Cs and M=Pb, Sn undergo a bulk superconducting transition ranging from 2.7 to 1.4 K depending on the composition. The estimated superconducting volume fraction is about 90 %. Superconducting phase diagrams as a function of chemical pressure are constructed for the solid solution products of each member of the homologous series, AMBi 3-x Sb x Te 6-y Se y and AM 2 Bi 3-x Sb x Te 7-y Se y (0≤x≤3 or 0≤y≤2). The structural flexibility of the ternary AM m M' 3 Te 5+m semiconducting homology to form isostructural analogues with a variety of metals, M=Pb, Sn; M'=Bi, Sb, gives access to a large number of electronic configurations and superconductivity due to chemical pressure effects. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Diffuse phase ferroelectric vs. Polomska transition in (1-x) BiFeO3-(x) Ba Zr0.025Ti0.975O3 (0.1 ≤ x ≤ 0.3) solid solutions

NASA Astrophysics Data System (ADS)

Jha, Pardeep K.; Jha, Priyanka A.; Singh, Vikash; Kumar, Pawan; Asokan, K.; Dwivedi, R. K.

2015-01-01

Investigations on the solid solutions (1-x) BiFeO3 - (x) Ba Zr0.025Ti0.975O3 (0.1 ≤ x ≤ 0.3) in the temperature range 300-750 K show colossal permittivity behavior and the occurrence of diffuse phase ferroelectric transition along with frequency dependent anomaly which disappears at temperature ˜450 K. For x = 0.3, these anomalies have been verified through differential scanning calorimetry and dielectric/impedance/conductivity measurements. The occurrence of peak in pyrocurrent (dPs/dT) vs. T plots also supports phase transition. With the increasing x, transition temperature decreases and diffusivity increases. This anomaly is absent at high frequencies (>100 kHz) in conductivity plots, indicating Polomska like surface phase transition, which is supported by modulus study.

Spectrally resolved localized states in GaAs 1– xBi x

DOE PAGES

Christian, Theresa M.; Alberi, Kirstin; Beaton, Daniel A.; ...

2017-02-01

In this study, the role of localized states and their influence on the broader band structure remains a crucial question in understanding the band structure evolution in GaAs 1-xBi x. Here in this work, we present clear spectroscopic observations of recombination at several localized states in GaAs 1-xBi x. Sharp and recognizable photoluminescence features appear in multiple samples and redshift as a function of GaBi fraction between x = 0.16% and 0.4% at a linearized rate of 34 meV per % Bi, weaker than the redshift associated with band-to-band recombination. Interpreting these results in terms of radiative recombination between localizedmore » holes and free electrons sheds light on the relative movement of the conduction band minimum and the characteristics of localized bismuth-related trap states in GaAs 1-xBi x alloys.« less

Thermoelectric properties of Bi1-xSnxCuSeO solid solutions.

PubMed

Yang, Yuqing; Liu, Xiaocun; Liang, Xin

2017-02-21

We report the enhanced thermoelectric properties of p-type BiCuSeO by tin doping on bismuth sites. Powder X-ray diffraction analysis and Hall measurements indicated effective tin doping in all samples. We found that the doping efficiency of Sn is lower than expected, as seen from the measured carrier concentration. First-principles calculations indicate that the Sn lone pair modifies the band structure at the Fermi level, with the consequent effect observed in the electrical transport and Seebeck coefficient measurements. An enhanced thermoelectric power factor of ∼2.5 μW cm -1 K -2 was reached at 773 K. No significant effect of Sn doping on the thermal conductivity was found; a thermoelectric figure of merit value (ZT) of 0.3 at 773 K is achieved for Bi 0.9 Sn 0.1 CuSeO, which is more than twice that of the pristine BiCuSeO.

Study of the superconducting properties of the Bi-Ca-Sr-Cu-O system

NASA Technical Reports Server (NTRS)

Khan, Musheer H.; Naqvi, S. M. M. R.; Zia-Ul-haq, S. M.

1991-01-01

High Temperature Superconductivity in the Bi-Ca-Sr-Cu-O System has been observed and has attracted considerable attention in 1988. The 80 K superconductivity phase has been identified to have a composition of Bi2CaSr2Cu2Ox, while the 110 K phase as reported in the literature has a possible composition of Bi2Ca2Sr2Cu3O(x). Researchers present here a study of the electrical properties of bulk samples of the slowly cooled and rapidly quenched 2:1:2:2 system. The samples used in this study were prepared from appropriate amounts of Bi2O3, CuO, SrCO3, CaCO3.

Combined effects of Bi deficiency and Mn substitution on the structural transformation and functionality of BiFeO{sub 3} films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Jingyi; Wang, Yao, E-mail: wang-yao@buaa.edu.cn; Deng, Yuan, E-mail: dengyuan@buaa.edu.cn

2014-11-07

Mn-doped BiFeO{sub 3} films with Mn contents of 5 and 10 mol. % were prepared via a chemical route. A carefully controlled amount of Bi deficiency was introduced to further tune the lattice structure and the functionality of multiferroic BiFeO{sub 3}. The crystal structure of Bi{sub 1−δ}Fe{sub 1−x}Mn{sub x}O{sub 3} films was investigated by X-ray diffraction and Raman spectra; a rhombohedral-to-orthorhombic phase transition was revealed. The observed double hysteresis loops and two capacitance maxima from polarization vs electric field and capacitance-voltage measurements indicate an antiferroelectric-like behavior. Additionally, the coexistence of ferroelectric (FE) and antiferroelectric (AFE) phases in Bi{sub 1−δ}Fe{sub 1−x}Mn{sub x}O{submore » 3} films was revealed from the domain structures obtained by piezoelectric force microscopy. The effects of Mn substitution in conjunction with Bi deficiency on the FE-AFE phase transition and electrical behavior of BiFeO{sub 3} films are discussed in detail. Meanwhile, magnetic and photoluminescence measurements on the films illustrate that Mn substitution gives rise to the net magnetic moment and the defects induced by both Bi deficiency and Mn substitution influence the electronic structure of BiFeO{sub 3} films. This study thus shows a simple and effective way to control the functionalities of BiFeO{sub 3} films.« less

Multifield Control of Domains in a Room-Temperature Multiferroic 0.85BiTi0.1Fe0.8Mg0.1O3-0.15CaTiO3 Thin Film.

PubMed

Jia, Tingting; Fan, Ziran; Yao, Junxiang; Liu, Cong; Li, Yuhao; Yu, Junxi; Fu, Bi; Zhao, Hongyang; Osada, Minoru; Esfahani, Ehsan Nasr; Yang, Yaodong; Wang, Yuanxu; Li, Jiang-Yu; Kimura, Hideo; Cheng, Zhenxiang

2018-06-20

Single-phase materials that combine electric polarization and magnetization are promising for applications in multifunctional sensors, information storage, spintronic devices, etc. Following the idea of a percolating network of magnetic ions (e.g., Fe) with strong superexchange interactions within a structural scaffold with a polar lattice, a solid solution thin film with perovskite structure at a morphotropic phase boundary with a high level of Fe atoms on the B site of perovskite structure is deposited to combine both ferroelectric and ferromagnetic ordering at room temperature with magnetoelectric coupling. In this work, a 0.85BiTi 0.1 Fe 0.8 Mg 0.1 O 3 -0.15CaTiO 3 thin film has been deposited by pulsed laser deposition (PLD). Both the ferroelectricity and the magnetism were characterized at room temperature. Large polarization and a large piezoelectric effective coefficient d 33 were obtained. Multifield coupling of the thin film has been characterized by scanning force microscopy. Ferroelectric domains and magnetic domains could be switched by magnetic field ( H), electric field ( E), mechanical force ( F), and, indicating that complex cross-coupling exists among the electric polarization, magnetic ordering and elastic deformation in 0.85BiTi 0.1 F e0.8 Mg 0.1 O 3 -0.15CaTiO 3 thin film at room temperature. This work also shows the possibility of writing information with electric field, magnetic field, and mechanical force and then reading data by magnetic field. We expect that this work will benefit information applications.

Exchange coupling in permalloy/BiFeO3 heterostructures

NASA Astrophysics Data System (ADS)

Heron, John; Wang, Chen; Carlton, David; Nowakowski, Mark; Gajek, Martin; Awschalom, David; Bokor, Jeff; Ralph, Dan; Ramesh, R.

2010-03-01

BiFeO3 is a ferroelectric and antiferromagnetic multiferroic with the ferroelectric and antiferromagnetic order parameters coupled at room temperature. This coupling results in the reorientation of the ferroelectric and magnetic domains as applied voltages switch the electric polarization. Previous studies using ferromagnet/BiFeO3 heterostructures have shown that the anisotropy of the ferromagnetic layer can be tuned by the ferroelectric domain structure of the BiFeO3 film [1, 2]. The physical mechanism driving this exchange bias with BiFeO3 is still under investigation. We use patterned permalloy structures, with varying aspect ratios, on BiFeO3 thin films to investigate the physics of this interaction. The results of our studies using MFM, PEEM, and MOKE to understand this mechanism as a means to electric field control of magnetic structures will be presented. [4pt] [1] H. Bea et al., Physical Review Letters 100, 017204 (2008).[0pt] [2] L.W. Martin et al., Nanoletters 8, 2050 (2008).

Chemical bath deposition of Cu{sub 3}BiS{sub 3} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deshmukh, S.G., E-mail: deshmukhpradyumn@gmail.com; Vipul, Kheraj, E-mail: vipulkheraj@gmail.com; Panchal, A.K.

2016-05-06

First time, copper bismuth sulfide (Cu{sub 3}BiS{sub 3}) thin films were synthesized on the glass substrate using simple, low-cost chemical bath deposition (CBD) technique. The synthesized parameters such as temperature of bath, pH and concentration of precursors were optimized for the deposition of uniform, well adherent Cu{sub 3}BiS{sub 3} thin films. The optical, surface morphology and structural properties of the Cu{sub 3}BiS{sub 3} thin films were studied using UV-VIS-NIR spectra, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The as- synthesized Cu{sub 3}BiS{sub 3} film exhibits a direct band gap 1.56 to 1.58 eV having absorption coefficient of the ordermore » of 10{sup 5} cm{sup −1}. The XRD declares the amorphous nature of the films. SEM images shows films were composed of close-packed fine spherical nanoparticles of 70-80 nm in diameter. The chemical composition of the film was almost stoichiometric. The optical study indicates that the Cu{sub 3}BiS{sub 3} films can be applied as an absorber layer for thin film solar cells.« less

Angle-resolved and core-level photoemission study of interfacing the topological insulator Bi1.5Sb0.5Te1.7Se1.3 with Ag, Nb, and Fe

NASA Astrophysics Data System (ADS)

de Jong, N.; Frantzeskakis, E.; Zwartsenberg, B.; Huang, Y. K.; Wu, D.; Hlawenka, P.; Sańchez-Barriga, J.; Varykhalov, A.; van Heumen, E.; Golden, M. S.

2015-08-01

Interfaces between a bulk-insulating topological insulator (TI) and metallic adatoms have been studied using high-resolution, angle-resolved, and core-level photoemission. Fe, Nb, and Ag were evaporated onto Bi1 .5Sb0 .5Te1 .7Se1 .3 (BSTS) surfaces both at room temperature and 38 K. The coverage and temperature dependence of the adsorption and interfacial formation process have been investigated, highlighting the effects of the overlayer growth on the occupied electronic structure of the TI. For all coverages at room temperature and for those equivalent to less than 0.2 monolayer at low temperature all three metals lead to a downward shift of the TI bands with respect to the Fermi level. At room temperature Ag appears to intercalate efficiently into the van der Waals gap of BSTS, accompanied by low-level substitution for the Te/Se atoms of the termination layer of the crystal. This Te/Se substitution with silver increases significantly for low temperature adsorption, and can even dominate the electrostatic environment of the Bi/Sb atoms in the BSTS near-surface region. On the other hand, Fe and Nb evaporants remain close to the termination layer of the crystal. On room temperature deposition, they initially substitute isoelectronically for Bi as a function of coverage, before substituting for Te/Se atoms. For low temperature deposition, Fe and Nb are too immobile for substitution processes and show a behavior consistent with clustering on the surface. For both Ag and Fe/Nb, these differing adsorption pathways still lead to the qualitatively similar and remarkable behavior for low temperature deposition that the chemical potential first moves downward (p -type dopant behavior) and then upward (n -type behavior) on increasing coverage.

Sonocatalytic activity of a heterostructured β-Bi2O3/Bi2O2CO3 nanoplate in degradation of bisphenol A.

PubMed

Lee, Gooyong; Ibrahim, Shaliza; Kittappa, Shanmuga; Park, Heekyung; Park, Chang Min

2018-06-01

Novel heterostructured β-Bi 2 O 3 /Bi 2 O 2 CO 3 nanoplates (hBN) were synthesized to observe the sonocatalytic degradation of bisphenol A (BPA) (widely used as a model pollutant) under ultrasonic (US) irradiation. Prior to obtaining the hBN, the Bi 2 O 2 CO 3 micropowder precursor was prepared under hydrothermal conditions and then converted to hBN by increasing the calcination temperature to 300 °C. The synthesized hBN samples were characterized by field emission scanning electron microscope with energy dispersive X-ray analysis (FESEM/EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet-visible spectrophotometer diffuse reflection spectroscopy (UV-vis DRS), and X-ray photoelectron spectroscopy (XPS). The hBN/US system exhibited greater sonocatalytic activity for the degradation of BPA than the US treatment with the single element bismuth oxide, β-Bi 2 O 3 prepared by annealing the Bi 2 O 2 CO 3 precursor at 400 °C for 1 h. The US frequency and US power intensity in the hBN/US system were the key operating parameters, which were responsible for the complete degradation of BPA during 6 h of reactions. The degradation efficiency of BPA under the US irradiation was positively correlated with the dose of hBN. Our findings indicate that heterostructured hBN can be used as an efficient sonocatalyst for the catalytic degradation of BPA in water and wastewater treatment. Copyright © 2018 Elsevier B.V. All rights reserved.

Structural Investigations of the MnO-Bi3O3-CdO Glass System by IR and Raman Spectroscopies

NASA Astrophysics Data System (ADS)

Ardelean, I.; Todor, Ioana; PǍŞCUŢǍ, P.

Homogeneous glasses are formed in the MnO-Bi3O3-CdO system, up to 50 mol% MnO. For these glasses, IR and Raman spectral measurements are carried out in order to elucidate the local structure. We identify by IR spectroscopy both the structural units BiO3 and BiO6. The Raman investigation confirms the prevalence of BiO6 groups in the glass network for all concentrations. The number of these structural groups progressively increases with MnO content.

Local structural distortion and electrical transport properties of Bi(Ni 1/2Ti 1/2)O 3 perovskite under high pressure

DOE PAGES

Zhu, Jinlong; Yang, Liuxiang; Wang, Hsiu -Wen; ...

2015-12-16

Perovskite-structure materials generally exhibit local structural distortions that are distinct from long-range, average crystal structure. The characterization of such distortion is critical to understanding the structural and physical properties of materials. In this work, we combined Pair Distribution Function (PDF) technique with Raman spectroscopy and electrical resistivity measurement to study Bi(Ni 1/2Ti 1/2)O 3 perovskite under high pressure. PDF analysis reveals strong local structural distortion at ambient conditions. As pressure increases, the local structure distortions are substantially suppressed and eventually vanish around 4 GPa, leading to concurrent changes in the electronic band structure and anomalies in the electrical resistivity. Wemore » find, consistent with PDF analysis, Raman spectroscopy data suggest that the local structure changes to a higher ordered state at pressures above 4 GPa.« less

Thickness dependent band gap of Bi{sub 2-x}Sb{sub x}Te{sub 3} (x = 0, 0.05, 0.1) thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, M. M.; Soni, P. H., E-mail: phsoni-msu@yahoo.com; Desai, C. F.

2016-05-23

Thin films of Bi{sub 2}Te{sub 3}(Sb) were prepared on alkali halide crystal substrates. Sb content and the film thickness were varied. Bi{sub 2}Te{sub 3} is a narrow gap semiconductor. Bi-Sb is a continuous solid solution of substitutional type and Sb therefore was used to test its effect on the band gap. The film thickness variation was also taken up. The infra-red absorption spectra were used in the wave number range 400 cm{sup −1} to 4000 cm{sup −1}. The band gap obtained from the absorption data was found to increase with decreasing thickness since the thickness range used was from 30more » nm to 170 nm. This is a range corresponding to nanostructures and hence quantum size effect was observed as expected. The band gap also exhibited Sb content dependence. The detail results are have been reported and explained.« less

New red Y 0.85Bi 0.1Eu 0.05V 1-yM yO 4 (M=Nb, P) phosphors for light-emitting diodes

NASA Astrophysics Data System (ADS)

Wang, Yuhua; Sun, Yunkui; Zhang, Jiachi; Ci, Zhipeng; Zhang, Zhiya; Wang, Lei

2008-06-01

The Y 0.85Bi 0.1Eu 0.05V 1-yM yO 4 (M=Nb, P) as new near-ultraviolet excited phosphors were synthesized and their luminescence properties under 365 nm excitation were investigated in detail. It indicated that by doping small amount of P 5+ into V 5+ sites, the excitation intensity of charge transfer (CT) band of Bi-O (330-400 nm) was greatly improved. By substituting Nb 5+ for V 5+, both the CT bands of Bi-O and Eu-O (240-320 nm) were significantly enhanced. As a result, the emission intensity of Y 0.85Bi 0.1Eu 0.05V 1-yM yO 4 (M=Nb, P) could be improved about 90% by doping 5 mol% P 5+ and 110% by doping 5 mol% Nb 5+. Comparing with the commercial Y 2O 2S:Eu 3+ phosphors, the Y 0.85Bi 0.1Eu 0.05V 0.95M 0.05O 4 (M=Nb, P) phosphors exhibited excellent color purity and much higher brightness. The results showed that these Y 0.85Bi 0.1Eu 0.05V 1-yM yO 4 (M=Nb, P) phosphors could be considered as promising red phosphors for application in LED.

Structural variations and dielectric properties of (Bi1-xL ax ) 2Si O5 (0 ≤x ≤0.1 ): Polycrystallines synthesized by crystallization of Bi-Si-O and Bi-La-Si-O glasses

NASA Astrophysics Data System (ADS)

Taniguchi, Hiroki; Tatewaki, Shingo; Yasui, Shintaro; Fujii, Yasuhiro; Yamaura, Jun-ichi; Terasaki, Ichiro

2018-04-01

This paper focuses on effects of isovalent La substitution on the crystal structure and dielectric properties of ferroelectric B i2Si O5 . Polycrystalline samples of (Bi1-xL ax ) 2Si O5 are synthesized by crystallization of Bi-Si-O and Bi-La-Si-O glasses with a composition range of 0 ≤x ≤0.1 . The crystal structure changes from monoclinic to tetragonal with increasing La-substitution rate x at room temperature. This structural variation stems from the change in orientation of Si O4 tetrahedra that form one-dimensional chains when they are in the ordered configuration, thus suggesting that lone-pair electrons play an important role in sustaining one-dimensional chains of Si O4 tetrahedra. Synchronizing with the disordering of Si O4 chains, ferroelectric phase transition temperature of (Bi1-xL ax ) 2Si O5 sharply decreases as x increases, and ferroelectricity finally vanishes at around x =0.03 . The present results demonstrate that lone-pair electrons of Bi play an important role in the ferroelectricity of B i2Si O5 through propping the ordered structure of one-dimensional Si O4 chains with stereochemical activity. Furthermore, an additional phase transition has been first discovered in the low-temperature region of (Bi1-xL ax ) 2Si O5 with x ≤0.01 , where the ordered one-dimensional Si O4 chains remain.

Thermoelectric transport properties of BaBiTe{sub 3}-based materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Yiming; Zhao, Li-Dong, E-mail: zhaolidong@buaa.edu.cn

BaBiTe{sub 3}, a material with low thermal conductivity, is an inferior thermoelectric material due to the poor electrical properties originated from its narrow band gap. We choose two types of dopants, K and La, trying to optimize its electrical transport properties. The minority carriers, which harm the Seebeck coefficient in this system, are suppressed by La doping. With the increase of both electrical conductivity and Seebeck coefficient, the power factor of 3% La doped BaBiTe{sub 3} reaches 3.7 μW cm{sup −1} K{sup −2} which increased by 40% from undoped BaBiTe{sub 3}. Besides high power factor, the thermal conductivity is alsomore » reduced in it. Eventually, a high ZT value, 0.25 at 473 K, for n-type BaBiTe{sub 3} is achieved in 3% La doped BaBiTe{sub 3}. - Graphical abstract: BaBiTe{sub 3} possesses a low thermal conductivity. However, it is an inferior thermoelectric material due to the poor electrical properties originated from its narrow band gap. A high ZT value of 0.25 at 473 K for n-type BaBiTe{sub 3} can be achieved through optimizing electrical transport properties via La doping. - Highlights: • BaBiTe{sub 3} is an analogue of these promising thermoelectric materials: such as CsBi{sub 4}Te{sub 6} and K{sub 2}Bi{sub 8}Se{sub 13}, etc. • BaBiTe{sub 3} possesses a low thermal conductivity. • La is an effective dopant to enhance electrical transport properties. • A high ZT value of 0.25 at 473 K can be achieved in n-type La-doped BaBiTe{sub 3}.« less

Stabilization of a Metastable Fibrous Bi 21.2(1)(Mn 1–xCo x ) 20 Phase with Pseudo-Pentagonal Symmetry Prepared Using a Bi Self-Flux

DOE PAGES

Thimmaiah, Srinivasa; Taufour, Valentin; Iowa State Univ., Ames, IA; ...

2016-11-15

Bi 21.2(1)(Mn 1–xCo x ) 20 is a new metastable phase which is synthesized via Bi self-flux, adopts a highly fibrous morpholo-gy, and decomposes endothermically near 168 °C. It crystallizes in the orthorhombic space group Imma with unit cell parameters α = 19.067(4) Å, $b$ = 4.6071(10) Å and c = 11.583(4) Å, adopting a low-temperature modification of BiNi-type structure by forming columns along the b-axis. Wave-length-dispersive X-ray spectroscopy (WDS) confirms the presence of Co in the structure, which is found to be 7 at.%. In each column, the transition metal (T) and Bi atoms construct a double-walled nanotubular arrangementmore » of atoms around the disordered central Bi atoms. Electronic structure calculations (LMTO-ASA, LSDA) show that the calculated Fermi level falls into a pseudogap and also indicate a possible low-temperature magnetic ordering in the phase.« less

Synthesis, structures, and phase transitions of barium bismuth iridium oxide perovskites Ba{sub 2}BiIrO{sub 6} and Ba{sub 3}BiIr{sub 2}O{sub 9}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ling, Chris D., E-mail: c.ling@chem.usyd.edu.a; Bragg Institute, ANSTO, PMB 1, Menai 2234; Kennedy, Brendan J.

The Ba-Bi-Ir-O system is found to contain two distinct perovskite-type phases: a rock-salt ordered double perovskite Ba{sub 2}BiIrO{sub 6}; and a 6H-type hexagonal perovskite Ba{sub 3}BiIr{sub 2}O{sub 9}. Ba{sub 2}BiIrO{sub 6} undergoes a series of symmetry-lowering phase transitions on cooling Fm3-barm->R3-barc->12/m(C2/m)->I1-bar(P1-bar), all of which are second order except the rhombohedral->monoclinic one, which is first order. The monoclinic phase is only observed in a 2-phase rhombohedral+monoclinic regime. The transition and 2-phase region lie very close to 300 K, making the room-temperature X-ray diffraction patterns extremely complex and potentially explaining why Ba{sub 2}BiIrO{sub 6} had not previously been identified and reported. Amore » solid solution Ba{sub 2}Bi{sub 1+x}Ir{sub 1-x}O{sub 6}, analogous to Ba{sub 2}Bi{sub 1+x}Ru{sub 1-x}O{sub 6}, 0<=x<=2/3, was not observed. The 6H-type phase Ba{sub 3}BiIr{sub 2}O{sub 9} undergoes a clean second-order phase transition P6{sub 3}/mmc->C2/c at 750 K, unlike 6H-type Ba{sub 3}LaIr{sub 2}O{sub 9}, the P6{sub 3}/mmc structure of which is highly strained below {approx}750 K but fails to distort coherently to the monoclinic phase. - Graphical abstract: Structure of Ba{sub 3}BiIr{sub 2}O{sub 9} at 300 K. BiO{sub 6} octahedra are purple, IrO{sub 6} octahedra are gold, and Ba atoms are green. Thermal ellipsoids at 90% probability.« less

Presence of a monoclinic (Pm) phase in the morphotropic phase boundary region of multiferroic (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} solid solution: A Rietveld study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pandey, Rishikesh, E-mail: akhilesh-bhu@yahoo.com, E-mail: aksingh.mst@itbhu.ac.in; Singh, Akhilesh Kumar, E-mail: akhilesh-bhu@yahoo.com, E-mail: aksingh.mst@itbhu.ac.in

2014-07-28

We present here the results of structural studies on multiferroic (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} solid solution using Rietveld analysis on powder x-ray diffraction data in the composition range 0.35 ≤ x ≤ 0.55. The stability region of various crystallographic phases at room temperature for (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} is determined precisely. Structural transformation from pseudo-cubic (x ≤ 0.40) to tetragonal (x ≥ 0.50) phase is observed via phase coexistence region demarcating the morphotropic phase boundary. The morphotropic phase boundary region consists of coexisting tetragonal and monoclinic structures with space group P4mm and Pm, respectively, stable in composition range 0.41 ≤ x ≤ 0.49 as confirmed by Rietveld analysis. The resultsmore » of Rietveld analysis completely rule out the coexistence of rhombohedral and tetragonal phases in the morphotropic phase boundary region reported by earlier workers. A comparison between the bond lengths for “B-site cations-oxygen anions” obtained after Rietveld refinement, with the bond length calculated using Shannon-Prewitt ionic radii, reveals the ionic nature of B-O (Ni/Ti-O) bonds for the cubic phase and partial covalent character for the other crystallographic phases.« less

Energy dispersions of single-crystalline Bi2.0Sr1.8Ca0.8La0.3Cu2.1O8+δ superconductors determined using angle-resolved photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Lindberg, P. A. P.; Shen, Z.-X.; Dessau, D. S.; Wells, B. O.; Mitzi, D. B.; Lindau, I.; Spicer, W. E.; Kapitulnik, A.

1989-09-01

Angle-resolved photoemission studies of single-crystalline La-doped Bi-Sr-Ca-Cu- 90-K superconductors (Bi2.0Sr1.8Ca0.8La0.3Cu2.1O8+δ) were performed utilizing synchrotron radiation covering the photon energy range 10-40 eV. The data conclusively reveal a dispersionless character of the valence-band states as a function of the wave-vector component parallel to the c axis, in agreement with the predictions of band calculations. Band effects are evident from both intensity modulations of the spectral features in the valence band and from energy dispersions as a function of the wave vector component lying in the basal a-b plane.

Surface phonons in the topological insulators Bi2Se3 and Bi2Te3

NASA Astrophysics Data System (ADS)

Boulares, Ibrahim; Shi, Guangsha; Kioupakis, Emmanouil; Lošťák, Petr; Uher, Ctirad; Merlin, Roberto

2018-03-01

Raman scattering [K. M. F. Shahil et al., Appl. Phys. Lett. 96, 153103 (2010), V. Gnezdilov et al., Phys. Rev. B 84, 195118 (2011) and H. -H. Kung et al., Phys. Rev. B 95, 245406 (2017)], inelastic helium scattering [X. Zhu et al., Phys. Rev. Lett. 107, 186102 (2011)] and photoemission experiments [J. A. Sobota et al., Phys. Rev. Lett. 113, 157401 (2014)] on the topological insulators Bi2Se3 and Bi2Te3 show features in the range ∼ 50-160 cm-1, which have been assigned alternatively to Raman-forbidden, bulk infrared modes arising from symmetry breaking at the surface or to surface phonons, which couple to the topologically protected electronic states. Here, we present temperature- and wavelength- dependent Raman studies showing additional modes we ascribe to surface phonons in both Bi2Se3 and Bi2Te3. Our assignment is supported by density functional theory calculations revealing surface phonons at frequencies close to those of the extra peaks in the Raman data. The theoretical results also indicate that these modes are not a consequence of spin-orbit coupling and, thus, that their occurrence is unrelated to the topological properties of these materials.

The flux jumps in high Tc Bi(1.7)Pb(0.3)Sr2 Ca2Cu3O(y) bulk superconductor

NASA Astrophysics Data System (ADS)

Cao, Xiaowen; Huang, Sunli

1989-11-01

There were giant flux jumps in high T sub c Bi(1.7)Pb(0.3)Sr2Ca2Cu3O(v) bulk superconductor. The relaxation time, tau, decreased with both the increase of magnetic field and the rise of temperature. The maximum tau was about 40 min. The average -dM/dt increased with both the increase of magnetic field and the rise of temperature. The minimum average -dM/dt was about 4.1 x 10(exp -2) G/min. The flux jump weakened with time. It was dependent on the decrease of gradient of magnetic flux density dn/dx in the sample.

Influence of dioxygen on the promotional effect of Bi during Pt-catalyzed oxidation of 1,6-hexanediol

DOE PAGES

Xie, Jiahan; Huang, Benjamin; Yin, Kehua; ...

2016-05-24

In this study, a series of carbon-supported, Bi-promoted Pt catalysts with various Bi/Pt atomic ratios was prepared by selectively depositing Bi on Pt nanoparticles. The catalysts were evaluated for 1,6-hexanediol oxidation activity in aqueous solvent under different dioxygen pressures. The rate of diol oxidation on the basis of Pt loading over a Bi-promoted catalyst was 3 times faster than that of an unpromoted Pt catalyst under 0.02 MPa of O 2, whereas the unpromoted catalyst was more active than the promoted catalyst under 1 MPa of O 2. After liquid-phase catalyst pretreatment and 1,6-hexanediol oxidation, migration of Bi on themore » carbon support was observed. The reaction order in O 2 was 0 over Bi-promoted Pt/C in comparison to 0.75 over unpromoted Pt/C in the range of 0.02–0.2 MPa of O 2. Under low O 2 pressure, rate measurements in D 2O instead of H 2O solvent revealed a moderate kinetic isotope effect (rate H2O/rate D2O) on 1,6-hexanediol oxidation over Pt/C (KIE = 1.4), whereas a negligible effect was observed on Bi-Pt/C (KIE = 0.9), indicating that the promotional effect of Bi could be related to the formation of surface hydroxyl groups from the reaction of dioxygen and water. No significant change in product distribution or catalyst stability was observed with Bi promotion, regardless of the dioxygen pressure.« less

Direct Observation of Pressure-Driven Valence Electron Transfer in Ba 3 BiRu 2 O 9 , Ba 3 BiIr 2 O 9 , and Ba 4 BiIr 3 O 12

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blanchard, Peter E. R.; Chapman, Karena W.; Heald, Steve M.

The hexagonal perovskites Ba3BiIr2O9, Ba3BiRu2O9 and Ba4BiIr3O12 all undergo pressure-induced 1% volume collapses above 5 GPa. These first-order transitions have been ascribed to internal transfer of valence electrons between bismuth and iridium/ruthenium, which is driven by external applied pressure because the reduction in volume achieved by emptying the 6s shell of bismuth upon oxidation to Bi5+ is greater in magnitude than the increase in volume by reducing iridium or ruthenium. Here, we report direct observation of these valence transfers for the first time, using high-pressure X-ray absorption near-edge spectroscopy (XANES) measurements. Our data also support the highly unusual “4+” nominalmore » oxidation state of bismuth in these compounds, although the possibility of local disproportionation into Bi3+/Bi5+ cannot be definitively ruled out. Ab initio calculations reproduce the transition, support its interpretation as a valence electron transfer from Bi to Ir/Ru, and suggest that the high-pressure phase may show metallic behavior (in contrast to the insulating ambient-pressure phase).« less

High surface stability of magnetite on bi-layer Fe3O4/Fe/MgO(0 0 1) films under 1 MeV Kr+ ion irradiation

NASA Astrophysics Data System (ADS)

Kim-Ngan, N.-T. H.; Krupska, M.; Balogh, A. G.; Malinsky, P.; Mackova, A.

2017-12-01

We investigate the stability of the bi-layer Fe3O4/Fe(0 0 1) films grown epitaxially on MgO(0 0 1) substrates with the layer thickness in the range of 25-100 nm upon 1 MeV Kr+ ion irradiation. The layer structure and layer composition of the films before and after ion irradiation were studied by XRR, RBS and RBS-C techniques. The interdiffusion and intermixing was analyzed. No visible change in the RBS spectra was observed upon irradiation with ion fluence below 1015 Kr cm-2. The bi-layer structure and the stoichiometric Fe3O4 layer on the surface were well preserved after Kr+ ion irradiation at low damage levels, although the strong intermixing implied a large interfacial (Fe x O y ) and (Fe, Mg)O y layer respective at Fe3O4-Fe and Fe-MgO interface. The high ion fluence of 3.8  ×  1016 Kr cm-2 has induced a complete oxidization of the buffer Fe layer. Under such Kr fluence, the stoichiometry of the Fe3O4 surface layer was still preserved indicating its high stability. The entire film contains Fe x O y -type composition at ion fluence large than 5.0  ×  1016 Kr cm-2.

Ferroelectric photovoltaic properties in doubly substituted (Bi0.9La0.1)(Fe0.97Ta0.03)O3 thin films

NASA Astrophysics Data System (ADS)

Katiyar, R. K.; Sharma, Y.; Barrionuevo, D.; Kooriyattil, S.; Pavunny, S. P.; Young, J. S.; Morell, G.; Weiner, B. R.; Katiyar, R. S.; Scott, J. F.

2015-02-01

Doubly substituted [Bi0.9La0.1][Fe0.97Ta0.03]O3 (BLFTO) films were fabricated on Pt/TiO2/SiO2/Si substrates by pulsed laser deposition. The ferroelectric photovoltaic properties of ZnO:Al/BLFTO/Pt thin film capacitor structures were evaluated under white light illumination. The open circuit voltage and short circuit current density were observed to be ˜0.20 V and ˜1.35 mA/cm2, respectively. The band gap of the films was determined to be ˜2.66 eV, slightly less than that of pure BiFeO3 (2.67 eV). The PV properties of BLFTO thin films were also studied for various pairs of planar electrodes in different directions in polycrystalline thin films.

Understanding the structure–property relationships of the ferroelectric to relaxor transition of the (1-x)BaTiO3–(x)BiInO3 lead-free piezoelectric system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manjón-Sanz, Alicia; Berger, Caitlin; Dolgos, Michelle R.

A structural and electromechanical investigation has been performed on (1-x)BaTiO 3–(x)BiInO 3 in the region 0.03 ≤ x ≤ 0.12. A gradual structural phase transition has been observed where the structure changes from tetragonal (P4mm) and passes through two regions of coexisting phases: (1) P4mm + R3m in the range 0.03 ≤ x ≤ 0.075 and (2) Pmmore » $$\\bar{3}$$m + R3m for 0.10 ≤ x ≤ 0.12. The properties also transition from ferroelectric (x ≤ 0.03) to relaxor ferroelectric (x ≥ 0.05) as the dielectric permittivity maximum becomes temperature and frequency dependent. This transition was also confirmed via polarization-electric field measurements as well as strain-electric field measurements. At the critical composition of x = 0.065, a moderate strain of ~0.104% and an effective piezoelectric coefficient (d$$*\\atop{33}$$) of 260 pm/V were observed. Finally, the original purpose of this study was to demonstrate the polarization extension mechanism as predicted in the literature, but due to the ferroelectric to relaxor transition, this mechanism was not found to be present in this system. However, this demonstrates that BaTiO 3-based lead-free ceramics could be modified to obtain enhanced electromechanical properties for actuator applications.« less

Understanding the structure–property relationships of the ferroelectric to relaxor transition of the (1-x)BaTiO3–(x)BiInO3 lead-free piezoelectric system

DOE PAGES

Manjón-Sanz, Alicia; Berger, Caitlin; Dolgos, Michelle R.

2017-05-01

A structural and electromechanical investigation has been performed on (1-x)BaTiO 3–(x)BiInO 3 in the region 0.03 ≤ x ≤ 0.12. A gradual structural phase transition has been observed where the structure changes from tetragonal (P4mm) and passes through two regions of coexisting phases: (1) P4mm + R3m in the range 0.03 ≤ x ≤ 0.075 and (2) Pmmore » $$\\bar{3}$$m + R3m for 0.10 ≤ x ≤ 0.12. The properties also transition from ferroelectric (x ≤ 0.03) to relaxor ferroelectric (x ≥ 0.05) as the dielectric permittivity maximum becomes temperature and frequency dependent. This transition was also confirmed via polarization-electric field measurements as well as strain-electric field measurements. At the critical composition of x = 0.065, a moderate strain of ~0.104% and an effective piezoelectric coefficient (d$$*\\atop{33}$$) of 260 pm/V were observed. Finally, the original purpose of this study was to demonstrate the polarization extension mechanism as predicted in the literature, but due to the ferroelectric to relaxor transition, this mechanism was not found to be present in this system. However, this demonstrates that BaTiO 3-based lead-free ceramics could be modified to obtain enhanced electromechanical properties for actuator applications.« less

Investigation of continuous changes in the electric-field-induced electronic state in Bi(1-x)Ca(x)FeO(3-δ).

PubMed

Ikeda-Ohno, Atsushi; Lim, Ji Soo; Ohkochi, Takuo; Yang, Chan-Ho; Seidel, Jan

2014-09-07

Amongst the most interesting phenomena in correlated oxide systems are the doping-driven competitions between energetically similar ground states found in, e.g., high-Tc superconductors and colossal magnetoresistance manganites. It has recently been reported that doped multiferroics also exhibit this generic concept of phase competition. Here, we employ photoelectron emission microscopy (PEEM) to demonstrate evidence of systematic changes in the electronic structure of Bi(1-x)Ca(x)FeO(3-δ) treated by electrically controlled hole carrier doping, the outcome of which clearly correlates with the local modulation of electronic conductivity observed in the same material.

Investigations on the Synthesis and Properties of Fe2O3/Bi2O2CO3 in the Photocatalytic and Fenton-like Process

NASA Astrophysics Data System (ADS)

Sun, Dongxue; Shen, Tingting; Sun, Jing; Wang, Chen; Wang, Xikui

2018-01-01

Catalyst of Bi2O2CO3 and Fe2O3 modified Bi2O2CO3 (Fe2O3/Bi2O2CO3) were prepared by hydrothermal method and characterized by X-ray diffractions (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and UV-vis DRS. The catalytic activity of Bi2O2CO3 and Fe2O3/Bi2O2CO3 were comparatively investigated in the photodegradation and Fento-like process. Rhodamine B(RhB) was selected as the target pollutant under the irradiation of 300 W xenon lamp. The results indicated that Fe2O3 plays a great role in the enhancing the treatment efficiency and the and the maximum reaction rate was achieved at the Fe2O3 loading of 1.5%. The Fenton-like degradation rate constant of RhB with bare Bi2O2CO3 in dark is 0.4 min-1, while that with 1.5 Fe2O3/Bi2O2CO3 increases to 28.4 min-1 under visible light irradiation, a 71-fold improvement. It is expected to shed a new light for the constructing novel composite photocatalyst and also provide a potential method for the removal of dyes in the aqueous system.

Electric field induced short range to long range structural ordering and its influence on the Eu{sup +3} photoluminescence in the lead-free ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalaskar, Abhijeet; Rao, Badari Narayana; Ranjan, Rajeev, E-mail: rajeev@materials.iisc.ernet.in

2015-06-28

Eu{sup +3} was incorporated into the lattice of a lead-free ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3} (NBT) as per the nominal formula Na{sub 0.5}Bi{sub 0.5−x}Eu{sub x}TiO{sub 3}. This system was investigated with regard to the Eu{sup +3} photoluminescence (PL) and structural behaviour as a function of composition and electric field. Electric field was found to irreversibly change the features in the PL spectra and also in the x-ray diffraction patterns below the critical composition x = 0.025. Detailed analysis revealed that below the critical composition, electric field irreversibly suppresses the structural heterogeneity inherent of the host matrix NBT and brings about a longmore » range ferroelectric state with rhombohedral (R3c) distortion. It is shown that the structural disorder on the nano-scale opens a new channel for radiative transition which manifests as a new emission line branching off from the main {sup 5}D{sub 0}→{sup 7}F{sub 0} line along with a concomitant change in the relative intensity of the other crystal field induced Stark lines with different J values. The study suggests that Eu{sup +3} luminescence can be used to probe the relative degree of field induced structural ordering in relaxor ferroelectrics and also in high performance piezoelectric alloys where electric field couples very strongly with the lattice and structural degrees of freedom.« less

Kinetic study of Bi 1.8Pb 0.4Ca 2Sr 2Cu 3O y superconductor in water

NASA Astrophysics Data System (ADS)

Wang, C. M.; Wei, T. P.; Kao, H.-C. I.

1993-10-01

The reaction of Bi 1.8Pb 0.4Ca 2Sr 2Cu 3O y powder in water was studied quantitatively. It was found that the [H 3O +] ion would act as a catalyst in this reaction and the initial rate equation was R 0 = - {d[A] 0}/{dt } = k[A] 0[ H3O+] 0.20, where [ A] represented the surface area of the superconducting powder. The rate constant, k, obtained at 10, 25 and 40°C was 3.98, 8.8 and 19.6 × 10 -4 mol min -1 cm -2 M 0.8, respectively. The activation energy and pre-exponential factor calculated from the Arrhenius equation were respectively 39.1 kJ mol -1 and 6.4 × 10 3 mol min -1 cm -2 M 0.8.

Topological Weyl semimetals in Bi1 -xSbx alloys

NASA Astrophysics Data System (ADS)

Su, Yu-Hsin; Shi, Wujun; Felser, Claudia; Sun, Yan

2018-04-01

We investigated Weyl semimetal (WSM) phases in bismuth antimony (Bi1 -xSbx ) alloys by combination of atomic composition and arrangement. Via first-principles calculations, we found two WSM states with Sb concentrations of x =0.5 and 0.83 with specific inversion-symmetry-broken elemental arrangement. The Weyl points are close to the Fermi level in both of these two WSM states. Therefore, it is likely to obtain Weyl points in Bi-Sb alloy. The WSM phase provides a reasonable explanation for the current transport study of Bi-Sb alloy with the violation of Ohm's law [D. Shin, Y. Lee, M. Sasaki, Y. H. Jeong, F. Weickert, J. B. Betts, H.-J. Kim, K.-S. Kim, and J. Kim, Nat. Mater. 16, 1096 (2017), 10.1038/nmat4965]. This paper shows that the topological phases in Bi-Sb alloys depend on both elemental composition and their specific arrangement.

Effect of counter-ion on packing and crystal density of 5,5'-(3,3'-bi[1,2,4-oxadiazole]-5,5'-diyl)bis(1 H -tetrazol-1-olate) with five different cations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giles, Ian D.; DeHope, Alan J.; Zuckerman, Nathaniel B.

In energetic materials, the crystal density is an important parameter that affects the performance of the material. When making ionic energetic materials, the choice of counter-ion can have detrimental or beneficial effects on the packing, and therefore the density, of the resulting energetic crystal. Presented herein are a series of five ionic energetic crystals, all containing the dianion 5,5′-(3,3′-bi[1,2,4-oxadiazole]-5,5′-diyl)bis(1 H -tetrazol-1-olate), with the following cations: hydrazinium ( 1 ) (2N 2 H 5 + ·C 6 N 12 O 4 2− ), hydroxylammonium ( 2 ) 2NH 4 O + ·C 6 N 12 O 4 2− [Pagoria et al..more » (2017). Chem. Heterocycl. Compd , 53 , 760–778; included for comparison], dimethylammonium ( 3 ) (2C 2 H 8 N + ·C 6 N 12 O 4 2− ), 5-amino-1 H -tetrazol-4-ium ( 4 ) (2CH 4 N 5 + ·C 6 N 12 O 4 2− ·4H 2 O), and aminoguanidinium ( 5 ) (2CH 7 N 4 + ·C 6 N 12 O 4 2− ). Both the supramolecular interactions and the sterics of the cation play a role in the density of the resulting crystals, which range from 1.544 to 1.873 Mg m −1 . In 5 , the tetrazolate ring is disordered over two positions [occupancy ratio 0.907 (5):0.093 (5)] due to a 180° rotation in the terminal tetrazole rings.« less

Effect of counter-ion on packing and crystal density of 5,5'-(3,3'-bi[1,2,4-oxadiazole]-5,5'-diyl)bis(1 H -tetrazol-1-olate) with five different cations

DOE PAGES

Giles, Ian D.; DeHope, Alan J.; Zuckerman, Nathaniel B.; ...

2018-03-09

In energetic materials, the crystal density is an important parameter that affects the performance of the material. When making ionic energetic materials, the choice of counter-ion can have detrimental or beneficial effects on the packing, and therefore the density, of the resulting energetic crystal. Presented herein are a series of five ionic energetic crystals, all containing the dianion 5,5′-(3,3′-bi[1,2,4-oxadiazole]-5,5′-diyl)bis(1 H -tetrazol-1-olate), with the following cations: hydrazinium ( 1 ) (2N 2 H 5 + ·C 6 N 12 O 4 2− ), hydroxylammonium ( 2 ) 2NH 4 O + ·C 6 N 12 O 4 2− [Pagoria et al..more » (2017). Chem. Heterocycl. Compd , 53 , 760–778; included for comparison], dimethylammonium ( 3 ) (2C 2 H 8 N + ·C 6 N 12 O 4 2− ), 5-amino-1 H -tetrazol-4-ium ( 4 ) (2CH 4 N 5 + ·C 6 N 12 O 4 2− ·4H 2 O), and aminoguanidinium ( 5 ) (2CH 7 N 4 + ·C 6 N 12 O 4 2− ). Both the supramolecular interactions and the sterics of the cation play a role in the density of the resulting crystals, which range from 1.544 to 1.873 Mg m −1 . In 5 , the tetrazolate ring is disordered over two positions [occupancy ratio 0.907 (5):0.093 (5)] due to a 180° rotation in the terminal tetrazole rings.« less

Structural and optical properties of cobalt doped multiferroics BiFeO3 nanostructure thin films

NASA Astrophysics Data System (ADS)

Prasannakumara, R.; Naik, K. Gopalakrishna

2018-05-01

Bismuth ferrite (BiFeO3) and Cobalt doped BiFeO3 (BiFe1-XCoXO3) nanostructure thin films were deposited on glass substrates by the sol-gel spin coating method. The X-ray diffraction patterns (XRD) of the grown BiFeO3 and BiFe1-XCoXO3 nanostructure thin films showed distorted rhombohedral structure. The shifting of peaks to higher angles was observed in cobalt doped BiFeO3. The surface morphology of the BiFeO3 and BiFe1-XCoXO3 nanostructure thin films were studied using FESEM, an increase in grain size was observed as Co concentration increases. The thickness of the nanostructure thin films was examined using FESEM cross-section. The EDX studies confirmed the elemental composition of the grown BiFeO3 and BiFe1-XCoXO3 nanostructure thin films. The optical characterizations of the grown nanostructure thin films were carried out using FTIR, it confirms the existence of Fe-O and Bi-O bands and UV-Visible spectroscopy shows the increase in optical band gap of the BiFeO3 nanostructure thin films with Co doping by ploting Tauc plot.

Giant negative electrocaloric effect in PbZrO3/0.88BaTiO3-0.12Bi(Mg1/2,Ti1/2)O3 multilayered composite ferroelectric thin film for solid-state refrigeration

NASA Astrophysics Data System (ADS)

Huang, D.; Wang, J. B.; Zhong, X. L.; Li, B.; Zhang, Y.; Jin, C.; Zheng, D. F.; Meng, X. J.

2017-11-01

A giant negative electrocaloric (EC) effect in a PbZrO3/(0.88BaTiO3-0.12 Bi(Mg1/2,Ti1/2)O3) (PZ/(BT-BMT)) multilayered composite ferroelectric (MCFE) thin film which is grown on Pt(111)/Ti/SiO2/Si(100) substrates by the sol-gel method is investigated in this work. The negative EC effect in the PZ/(BMT-BT) MCFE thin film is greatly higher than that in the PZ AFE thin film with an adiabatic temperature change (ATC) ΔT = 1.5 K. The ATC ΔT of the PZ/(BMT-BT) MCFE thin film is -32 K under the applied electric field change ΔE = 1151 kV/cm. The result is conducive to enhance the EC refrigeration efficiency greatly.

Thermoelectric properties of Tl and I dual-doped Bi2Te3-based alloys

NASA Astrophysics Data System (ADS)

Wu, Fang; He, Qinglin; Tang, Mingsheng; Song, Hongzhang

2018-04-01

TlxBi2‑xTe3‑xIx (x = 0, 0.05, 0.1 and 0.2) flower-like nanopowders were prepared successfully by the hydrothermal method. Then, the synthesized nanoparticles were pressed into bulks by hot-pressing. The thermoelectric (TE) properties of the TlxBi2‑xTe3‑xIx bulk samples were investigated and discussed. The results showed that the influences of Tl doping on the electrical resistivity and Seebeck coefficients of the Bi2Te3 is over that of I doping. Thus, the power factors of the dual-doped bulks are all less than that of the Bi2Te3 bulk. The thermal conductivities of the TlxBi2‑xTe3‑xIx bulk samples also remain at lower values. As a result, the ZT value of the optimized doped bulk Tl0.1Bi1.9Te2.9I0.1 attains a value of 1.1 at 398 K.

Wavelength-dependent ultrafast charge carrier separation in the WO 3/BiVO 4 coupled system

DOE PAGES

Grigioni, Ivan; Stamplecoskie, Kevin G.; Jara, Danilo H.; ...

2017-05-08

Due to its ~2.4 eV band gap, BiVO 4 is a very promising photoanode material for harvesting the blue portion of the solar light for photoelectrochemical (PEC) water splitting applications. In WO 3/BiVO 4 heterojunction films, the electrons photoexcited in BiVO 4 are injected into WO 3, overcoming the lower charge carriers’ diffusion properties limiting the PEC performance of BiVO 4 photoanodes. Here, we investigate by ultrafast transient absorption spectroscopy the charge carrier interactions occurring at the interface between the two oxides in heterojunction systems to directly unveil their wavelength dependence. Under selective BiVO 4 excitation, a favorable electron transfermore » from photoexcited BiVO 4 to WO 3 occurs immediately after excitation and leads to an increase of the trapped holes’ lifetime in BiVO4. However, a recombination channel opens when both oxides are simultaneously excited, evidenced by a shorter lifetime of trapped holes in BiVO 4. As a result, PEC measurements reveal the implication of these wavelength-dependent ultrafast interactions on the performances of the WO 3/BiVO 4 heterojunction.« less

Wavelength-dependent ultrafast charge carrier separation in the WO 3/BiVO 4 coupled system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grigioni, Ivan; Stamplecoskie, Kevin G.; Jara, Danilo H.

Due to its ~2.4 eV band gap, BiVO 4 is a very promising photoanode material for harvesting the blue portion of the solar light for photoelectrochemical (PEC) water splitting applications. In WO 3/BiVO 4 heterojunction films, the electrons photoexcited in BiVO 4 are injected into WO 3, overcoming the lower charge carriers’ diffusion properties limiting the PEC performance of BiVO 4 photoanodes. Here, we investigate by ultrafast transient absorption spectroscopy the charge carrier interactions occurring at the interface between the two oxides in heterojunction systems to directly unveil their wavelength dependence. Under selective BiVO 4 excitation, a favorable electron transfermore » from photoexcited BiVO 4 to WO 3 occurs immediately after excitation and leads to an increase of the trapped holes’ lifetime in BiVO4. However, a recombination channel opens when both oxides are simultaneously excited, evidenced by a shorter lifetime of trapped holes in BiVO 4. As a result, PEC measurements reveal the implication of these wavelength-dependent ultrafast interactions on the performances of the WO 3/BiVO 4 heterojunction.« less

Out-of-Plane Disorder Effects on the Energy Gaps and Electronic Charge Order in Bi2Sr1.7R0.3CuO6+δ (R = La and Eu)

NASA Astrophysics Data System (ADS)

Kurosawa, Tohru; Takeyama, Kohsaku; Baar, Stefan; Shibata, Yuto; Kataoka, Moeko; Mizuta, Shusei; Yoshida, Hiroshi; Momono, Naoki; Oda, Migaku; Ido, Masayuki

2016-04-01

We performed STM/STS experiments at 8 K in Bi2Sr1.7R0.3CuO6+δ (R-Bi2201) systems that had optimal (OP) hole-doping levels (˜0.17) but different Tc values, 35 K for R = La and 20 K for R = Eu, and examined out-of-plane disorder effects on the superconducting (SC) gap (SCG) and the pseudogap (PG) which is associated with the so-called "checkerboard charge order" (CCO). As out-of-plane disorders are strengthened by replacing La with Eu in OP R-Bi2201, the antinodal PG size ΔPG increases from ˜30 to ˜60 meV, the nodal SCG size ΔSC seems to decrease from ˜7 to ˜4 meV, and the pairing gap amplitude Δ0 or d-wave gap size at the antinodes is almost unchanged (Δ0 ˜ 15 meV). These gap sizes for OP doping in Eu-Bi2201 are comparable to those for an underdoping level of ˜0.1 in La-Bi2201. Although out-of-plane disorders strongly affect the electronic system of the Cu-O plane, they have no effect on the period of the CCO, which is five times the lattice constant (5a) along the Cu-O bond directions for OP doping and 4a for p ˜ 0.1. We suggest that the concentration of holes doped into the Cu-O plane may be an essential factor for determining the period of the CCO.

Bi12TiO20 crystallization in a Bi2O3-TiO2-SiO2-Nd2O3 system

NASA Astrophysics Data System (ADS)

Slavov, S.; Jiao, Z.

2018-03-01

Polycrystalline mono-phase bismuth titanate was produced by free cooling from melts heated to 1170 °C. The control over the initial amounts in the starting compositions in the system Bi2O3/TiO2/SiO2/Nd2O3 and over the thermal gradient of the heat process resulted in the formation of specific structures and microstructures of monophase sillenite ceramics. The main phase Bi12TiO20 belongs to the amorphous network groups based on oxides of silicon, bismuth and titanium. In this work, we demonstrated a way to control the crystalline and amorphous phase formation in bulk poly-crystalline materials in the selected system.

High-Pressure Polymorph of NaBiO3.

PubMed

Naa, Octavianti; Kumada, Nobuhiro; Miura, Akira; Takei, Takahiro; Azuma, Masaki; Kusano, Yoshihiro; Oka, Kengo

2016-06-20

A new high-pressure polymorph of NaBiO3 (hereafter β-NaBiO3) was synthesized under the conditions of 6 GPa and 600 °C. The powder X-ray diffraction pattern of this new phase was indexed with a hexagonal cell of a = 9.968(1) Å and c = 3.2933(4) Å. Crystal structure refinement using synchrotron powder X-ray diffraction data led to RWP = 8.53% and RP = 5.55%, and the crystal structure was closely related with that of Ba2SrY6O12. No photocatalytic activity for phenol decomposition was observed under visible-light irradiation in spite of a good performance for its mother compound, NaBiO3. The optical band-gap energy of β-NaBiO3 was narrower than that of NaBiO3, which was confirmed with density of states curves simulated by first-principles density functional theory calculation.

Structural, morphological, dielectric and impedance spectroscopy of lead-free Bi(Zn2/3Ta1/3)O3 electronic material

NASA Astrophysics Data System (ADS)

Halder, S.; Bhuyan, S.; Das, S. N.; Sahoo, S.; Choudhary, R. N. P.; Das, P.; Parida, K.

2017-12-01

A lead-free dielectric material [Bi(Zn2/3Ta1/3)O3] has been prepared using a solid state reaction technique at high-temperature. The resistive, conducting and capacitive characteristics of the prepared electronic material have been studied in different experimental conditions. The determination of basic crystal parameters and reflection indices confirm the development of polycrystalline compound with orthorhombic crystal structure. The study of frequency-temperature dependence of ac conductivity illustrates the nature and conduction mechanism of the material. On the basis of observed impedance data and detailed dielectric analysis, the existence of non-Debye type relaxation has been affirmed. The electronic charge carriers of compound have short range order that has been validated from the complex modulus and impedance spectrum. The detailed studies of resistive, capacitive, microstructural characteristics of the prepared material provide some useful data for considering the material as an electronic component for fabrication of devices.

Accurate solid solution range of BiMnxFe3-xO6 and low temperature magnetism

NASA Astrophysics Data System (ADS)

Jiang, Pengfei; Yue, Mufei; Cong, Rihong; Gao, Wenliang; Yang, Tao

2017-11-01

BiMnxFe3-xO6 (x = 1) represents a new type of oxide structure containing Bi3+ and competing magnetic super-exchanges. In literature, multiple magnetic states were realized at low temperatures in BiMnFe2O6, and the hypothetical parent compounds (BiMn3O6, BiFe3O6) were predicted to be different in magnetism. Herein, we performed a careful study on the syntheses of BiMnxFe3-xO6 at ambient pressure, and the solid solution range was determined to be 0.9 ≤ x ≤ 1.3 by Rietveld refinements on high-quality powder X-ray diffraction data. Due to the very similar cationic size of Mn3+ and Fe3+, and possibly the structural rigidity, there was no significant structure change in the whole range of solid solution. The magnetic behavior of BiMnxFe3-xO6 (x = 1.2, 1.22, 1.26, 1.28 and 1.3) was generally similar to BiMnFe2O6, while the relative higher concentration of Mn3+ led to the decreasing of the antiferromagnetic ordering temperature.

Laser-Marking Mechanism of Thermoplastic Polyurethane/Bi2O3 Composites.

PubMed

Zhong, Wei; Cao, Zheng; Qiu, Pengfei; Wu, Dun; Liu, Chunlin; Li, Huili; Zhu, He

2015-11-04

Using bismuth oxide (Bi2O3) as a laser-marking additive and thermoplastic polyurethane (TPU) as the matrix, TPU/Bi2O3 composite materials were prepared by melt blending in a torque rheometer. The sheet samples prepared from the TPU/Bi2O3 composites were treated in air by scanning with a neodymium-doped yttrium aluminum garnet (Nd: YAG) pulsed laser beam at a wavelength of 1064 nm. Compared with the pure TPU sample, the laser-marked composite samples exhibited differences in marking contrast as the Bi2O3 content increased from 0.1% to 1.0% based on stereomicroscope analysis. Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, thermogravimetry analysis, and X-ray diffraction were used to characterize the laser-marked surface material of the composite samples. Furthermore, a mechanism for the laser-effected darkening of the TPU/Bi2O3 composites was proposed. The results herein indicated that the addition of the Bi2O3 laser-sensitive additive to TPU resulted in laser darkening of the TPU/Bi2O3 composites. The marking contrast and visual appearance of the surface of the TPU/Bi2O3 composites after laser irradiation was due to a synergistic effect consisting of carbonization via TPU pyrolysis and reduction of Bi2O3 to black bismuth metal.

43 CFR 3422.3-1 - Bidding systems.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Bidding systems. 3422.3-1 Section 3422.3-1... systems. (a) The provisions of 10 CFR part 378 1 are not applicable to this part. 1 Redesignated as 30 CFR... cash bonus—fixed royalty bidding systems or any other bidding system adopted through rulemaking...

43 CFR 3422.3-1 - Bidding systems.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Bidding systems. 3422.3-1 Section 3422.3-1... systems. (a) The provisions of 10 CFR part 378 1 are not applicable to this part. 1 Redesignated as 30 CFR... cash bonus—fixed royalty bidding systems or any other bidding system adopted through rulemaking...

Phase transformation, improved ferroelectric and magnetic properties of (1 − x) BiFeO{sub 3}–xPb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} solid solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Subhash, E-mail: rk.dwivedi@jiit.ac.in, E-mail: subhash1jiit@gmail.com; Singh, Vikash; Dwivedi, R. K., E-mail: rk.dwivedi@jiit.ac.in, E-mail: subhash1jiit@gmail.com

2014-06-14

The authors prepared (1 − x)BiFeO{sub 3} – (x)Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} for x ≤ 0.30 by sol-gel method and investigated the material's structures, magnetic and electrical properties. Detailed Rietveld analysis of X-ray diffraction data revealed that the system retains distorted rhombohedral R3c structure for x ≤ 0.10 but transforms to monoclinic (Cc) structure for x > 0.10. Disappearance of some Raman modes corresponding to A1 modes and the decrease in the intensities of the remaining A1 modes with increasing x in the Raman spectra, which is a clear indication of structural modification and symmetry changes brought about by PZT doping. Enhanced magnetization with PZT doping content maymore » be attributed to the gradual change and destruction in the spin cycloid structure of BiFeO{sub 3.} The leakage current density at 3.5 kV/cm was reduced by approximately three orders of magnitude by doping PZT (x = 0.30), compared with BFO ceramics.« less

Bi{sub 6}(SeO{sub 3}){sub 3}O{sub 5}Br{sub 2}: A new bismuth oxo-selenite bromide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berdonosov, Peter S., E-mail: berdonosov@inorg.chem.msu.ru; Olenev, Andrei V.; Kirsanova, Maria A.

2012-12-15

A new bismuth oxo-selenite bromide Bi{sub 6}(SeO{sub 3}){sub 3}O{sub 5}Br{sub 2} was synthesized and structurally characterized. The crystal structure belongs to the triclinic system (space group P1-bar , Z=2, a=7.1253(7) A, b=10.972(1) A, c=12.117(1) A, {alpha}=67.765(7) Degree-Sign , {beta}=82.188(8) Degree-Sign , {gamma}=78.445(7) Degree-Sign ) and is unrelated to those of other known oxo-selenite halides. It can be considered as an open framework composed of BiO{sub x} or BiO{sub y}Br{sub z} polyhedrons forming channels running along [1 0 0] direction which contain the selenium atoms in pyramidal shape oxygen coordination (SeO{sub 3}E). The spectroscopic properties and thermal stability were studied. Themore » new compound is stable up to 400 Degree-Sign C. - graphical abstract: New bismuth oxo-selenite bromide with new open framework structure. Highlights: Black-Right-Pointing-Pointer New bismuth oxo-selenite bromide was found and structurally characterized. Black-Right-Pointing-Pointer Bi{sub 6}(SeO{sub 3}){sub 3}O{sub 5}Br{sub 2} exhibit a new open framework structure type. Black-Right-Pointing-Pointer BiO{sub x} or BiO{sub y}Br{sub z} polyhedrons form channels in the structure which are decorated by [SeO{sub 3}E] groups.« less

Synthesis and Study on Ionic Conductive (Bi1−x,Vx)O1.5−δ Materials with a Dual-Phase Microstructure

PubMed Central

Lai, Yu-Wei; Wei, Wen-Cheng J.

2016-01-01

Homogeneous Bi2O3-V2O5 powder mixtures with different amounts of V2O5 content (≤15 mol%) were prepared by colloidal dispersion and sintering to high density. The sintered and annealed samples were studied by thermal analysis, quantitative X-ray diffraction and scanning electron microscopy. The electrical and ionic conductivities of the conductors were also measured by a four-probe direct current (DC) method. The results of the samples prepared at 600–800 °C and annealed for as long as 100 h show that the sintered samples consisting of a pure γ phase or δ + γ binary phase perform differently in conductivity. The highly conductive δ phase in the composition of Bi0.92V0.08O1.5−δ enhances the electric conductivity 10-times better than that of the pure γ-sample (Bi0.94V0.06O1.5−δ) between 400 and 600 °C. The compatible regions of the γ phase with the α- or δ phase are also reported and discussed, so a part of the previously published Bi2O3-V2O5 phase diagram below 800 °C is revised. PMID:28773981

Optimum discharge energy density at room temperature in relaxor K1/2Bi1/2TiO3 for green energy harvesting

NASA Astrophysics Data System (ADS)

Banerjee, Krishnarjun; Asthana, Saket; Karuna Kumari, P.; Niranjan, Manish K.

2018-03-01

Lead-free polycrystalline K1/2Bi1/2TiO3 was prepared by the solid state reaction method. Experimentally observed frequencies of Raman modes signified its tetragonal phase, and matched reasonably well with theoretically calculated values. The relaxor nature of this material was observed in the temperature-dependent real part of the permittivity and dielectric loss curve. The value of the degree of diffuseness (1.99) was estimated from the modified Curie-Weiss law confirmed its relaxor behavior. The validation of this behavior was justified by the Vogel-Fülcher relation. The shoulder in the imaginary part of the modulus (M″) and permittivity (ɛ″) spectra revealed the presence of polar nano regions (PNRs). The evidence of PNRs was detectable above freezing temperatures, and became weaker when the temperature exceeded T m (temperature at the maximum of the dielectric constant). The electric field-induced polarization and strain curve showed the stabilization of the long-range ferroelectric order of the specimen at room temperature. Moreover, the discharge energy density and strain were 0.46 J cm-3 and 0.12%, respectively, at the maximum application of the electric field of 115 kV cm-1 at room temperature.

STM studies of topological phase transition in (Bi,In)2Se3

NASA Astrophysics Data System (ADS)

Zhang, Wenhan; Wang, Xueyun; Cheong, Sang-Wook; Wu, Weida; Weida Wu Team; Sang-Wook Cheong Collaboration

Topological insulators (TI) are a class of materials with insulating bulk and metallic surface state, which is the result of band inversion induced by strong spin-orbit coupling (SOC). The transition from topological phase to non-topological phase is of great significance. In theory, topological phase transition is realized by tuning SOC strength. It is characterized by the process of gap closing and reopening. Experimentally it was observed in two systems: TlBi(S1-xSex)2 and (Bi1-xInx)2 Se3 where the transition is realized by varying isovalent elements doping concentration. However, none of the previous studies addressed the impact of disorder, which is inevitable in doped systems. Here, we present a systematic scanning tunneling microscopy/spectroscopy study on (Bi1-xInx)2 Se3 single crystals with different In concentrations across the transition. Our results reveal an electronic inhomogeneity due to the random distribution of In defects which locally suppress the topological surface states. Our study provides a new angle of understanding the topological transition in the presence of strong disorders. This work is supported by NSF DMR-1506618.

On the electronic structure and thermoelectric properties of BiTeBr and BiTeI single crystals and of BiTeI with the addition of BiI{sub 3} and CuI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kulbachinskii, Vladimir A., E-mail: kulb@mig.phys.msu.ru; Kytin, Vladimir G.; Kudryashov, Alexey A.

The electronic structures were calculated for BiTeBr and BiTeI using the density-functional theory approach and accounting for the strong spin-orbital interaction. Qualitatively, the band structures for two compounds are similar, showing strong mixing of the p states of all elements in vicinity of the Fermi level, with the band gaps of 0.595 and 0.478 eV for BiTeBr and BiTeI, respectively. The optimized crystal structures show a tendency for the Bi-X (X=Br, I) bond elongation compared to the Bi-Te one. Both compounds are intrinsic n-type semiconductors but display a metallic-like conductivity coupled to rather large thermopower, which is rationalized within themore » frames of the acoustic phonons scattering model. Because of larger thermopower BiTeBr exhibits a twice higher thermoelectric figure-of-merit near room temperature, ZT=0.17, compared to BiTeI. The addition of 1 mass% of BiI{sub 3} or CuI to BiTeI decreases the mobility of electrons by two orders of magnitude, leading to significantly lower electrical conductivity, but at the same time effectively reduces the thermal conductivity. The prospects of further enhancing the thermoelectric efficiency are briefly discussed. - Graphical abstract: View of the crystal structure of BiTeBr is shown in the figure The optimized crystal structures show a tendency for the Bi-X (X=Br, I) bond elongation compared to the Bi-Te one. The electronic structures were calculated for BiTeBr and BiTeI using the density-functional theory approach and accounting for the strong spin-orbital interaction. Qualitatively, the band structures for two compounds are similar, showing strong mixing of the p states of all elements in vicinity of the Fermi level, with the band gaps of 0.595 and 0.478 eV for BiTeBr and BiTeI, respectively. Both compounds are intrinsic n-type semiconductors but display a metallic-like conductivity coupled to rather large thermopower, which is rationalized within the frames of the acoustic phonons scattering

Rapid liquid phase sintered Mn doped BiFeO3 ceramics with enhanced polarization and weak magnetization

NASA Astrophysics Data System (ADS)

Kumar, Manoj; Yadav, K. L.

2007-12-01

Single-phase BiFe1-xMnxO3 multiferroic ceramics have been synthesized by rapid liquid phase sintering method to study the influence of Mn substitution on their crystal structure, dielectric, magnetic, and ferroelectric behaviors. From XRD analysis it is seen that Mn substitution does not affect the crystal structure of the BiFe1-xMnxO3 system. An enhancement in magnetization was observed for BiFe1-xMnxO3 ceramics. However, the ferooelectric hysteresis loops were not really saturated, we observed a spontaneous polarization of 10.23μC /cm2 under the applied field of 42kV/cm and remanent polarization of 3.99μC/cm2 for x =0.3 ceramic.

Layer Structured Bismuth Selenides of Bi₂Se₃ and Bi₃Se₄ for High Energy and Flexible All-Solid-State Micro-Supercapacitors.

PubMed

Hao, Chunxue; Wang, Lidan; Wen, Fusheng; Xiang, Jianyong; Li, Lei; Hu, Wentao; Liu, Zhongyuan

2017-12-20

Bismuth selenides (Bi2Se3 and Bi3Se4), both of which have the layered rhombohedral crystal structure, and found to be useful as electrode materials for supercapacitor application in this work. Bi2Se3 nanoplates as electrode material exhibit much better performance than that of Bi3Se4 nanoparticles in liquid electrolyte system (6 M KOH), which delivers a higher specific capacitance (272.9 F/g) than that of Bi3Se4 (193.6 F/g) at 5 mV/s. This result would may be attributed to that Bi2Se3 nanoplates possess more active electrochemical surfaces for the reversible surface redox reactions owing to its planar quintuple stacked layers (septuple layers for Bi3Se4). For the demand of electronic skin, we used a novel flexible annular interdigital structure electrode applying for all-solid-state micro-supercapacitors (AMSCs). Bi2Se3 AMSCs device delivers a much more excellent supercapacitor performance, exhibits a large stack capacitance 89.5 F/cm3 (Bi3Se4: 79.1 F/cm3) at 20 mV/s, a high energy density 17.9 mWh/cm3 and high power density 18.9 W/cm3. The bismuth selenides also exhibit good cycle stability, retention 95.5% (90.3%) after 1000 c for Bi2Se3 (Bi3Se4). Obviously, Bi2Se3 nanoplates can be promising electrode materials for flexible annular interdigital all-solid-sate supercapacitor. © 2017 IOP Publishing Ltd.

On the enhancement of energy storage density in Bi0.9Ho0.1FeO3 ceramics

NASA Astrophysics Data System (ADS)

Ethilton, S. John; Rajesh, R.; Ramachandran, K.; Giridharan, N. V.

2018-04-01

Polycrystalline Bi1-xHoxFeO3 (x = 0, 0.05, 0.1) samples are prepared by conventional solid state route. The XRD pattern shows R3c phase. The maximum electrical polarizations in the above three materials are found to be 0.067μC / cm2, 0.329μC / cm2 and 0.565μC / cm2 respectively. Here the holmium is chosen for the reason that the leakage current can be reduced very much thereby the multiferroic property can be enhanced. Based on this experience it is decided to study the energy storage density in these ceramic materials with Ho as dopant. It is found that there is a good enhancement from 12% to 30% efficiency on energy storage density.

Topological interface states in the natural heterostructure (PbSe)5(Bi2Se3 )6 with BiPb defects

NASA Astrophysics Data System (ADS)

Momida, Hiroyoshi; Bihlmayer, Gustav; Blügel, Stefan; Segawa, Kouji; Ando, Yoichi; Oguchi, Tamio

2018-01-01

We study theoretically the electronic band structure of (PbSe) 5(Bi2Se3 )6, which consists of an ordinary insulator PbSe and a topological insulator Bi2Se3 . The first-principles calculations show that this material has a gapped Dirac-cone energy dispersion inside the bulk, which originates from the topological states of Bi2Se3 layers encapsulated by PbSe layers. Furthermore, we calculate the band structures of (BixPb1 -xSe )5(Bi2Se3 )6 with BiPb antisite defects included in the PbSe layers. The result shows that a high density of BiPb defects can exist in real materials, consistent with the experimentally estimated x of more than 30%. The BiPb defects strongly modify the band alignment between Bi2Se3 and PbSe layers, while the topological interface states of Bi2Se3 are kept as a gapped Dirac-cone-like dispersion.

Nanostructured Composites of Bi1-xSbx Nanoparticles and Carbon Nanotubes and the Characterization of Their Thermoelectric Properties.

PubMed

Güneş, Ekrem; Gundlach, Felix; Elm, Matthias T; Klar, Peter J; Schlecht, Sabine; Wickleder, Mathias S; Müller, Eckhard

2017-12-27

The impact of inclusions of carbon nanotubes (CNT) on the thermoelectric properties of nanostructured Bi 1-x Sb x alloys with an Sb content between 10 and 20% was investigated for varying amounts of CNT. Three series of Bi 1-x Sb x pellets with 0, 0.3, and 0.5 wt % CNT were synthesized by mechanical alloying followed by uniaxial pressing. The resistivity was investigated in the temperature range from 30 to 500 K, revealing an enlargement of the band gap due to nanostructuring of the Bi 1- x Sb x alloy, which is even more pronounced for alloys including CNT. This enlargement is attributed to a modification of the interface between the Bi 1-x Sb x nanoparticles by a graphene-like coating, which is formed during the fabrication process due to the addition of CNT. Measurements of the Seebeck coefficient and the thermal conductivity were also performed to determine the thermoelectric properties. In total, the CNT-containing samples show a significant improvement of the figure of merit up to 250% for the Bi 0.88 Sb 0.12 composition with 0.3 wt % CNT due to the interface modification between the nanoparticles, demonstrating the beneficial effect of CNT on the thermoelectric properties.

Synthesis and luminescence properties of CaSnO3 :Bi3+ blue phosphor and the emission improvement by Li+ ion.

PubMed

Cao, Renping; Zhang, Jinlong; Wang, Wudi; Hu, Qianglin; Li, Wensheng; Ruan, Wen; Ao, Hui

2017-09-01

CaSnO 3 :Bi 3+ blue-emitting phosphor was synthesized using a high-temperature solid-state reaction method in air. The crystal structures and luminescence properties were investigated. A broad emission band peaking at ~448 nm upon excitation at 262 and 308 nm was observed in the range 330-680 nm at room temperature due to 3 P 1  →  1 S 0 transition of the Bi 3+ ion. The chromaticity coordinate was (0.1786, 0.1665). The optimal Bi 3+ ion concentration was ~0.6 mol% in CaSnO 3 :Bi 3+ phosphor. The emission spectrum of CaSnO 3 :Bi 3+ phosphor showed a blue-shift with increasing temperature from 50 to 300 K due to the influence of temperature on the electron transition of the Bi 3+ ion. The emission intensity of CaSnO 3 :Bi 3+ phosphor may be increased ~1.45 times by co-doping Li + ions as a charge compensator and fluxing agent. The luminescence mechanism is explained by a configurational coordinate diagram of Bi 3+ ion in CaSnO 3 :Bi 3+ phosphor. Copyright © 2017 John Wiley & Sons, Ltd.

SILAR deposited Bi2S3 thin film towards electrochemical supercapacitor

NASA Astrophysics Data System (ADS)

Raut, Shrikant S.; Dhobale, Jyotsna A.; Sankapal, Babasaheb R.

2017-03-01

Bi2S3 thin film electrode has been synthesized by simple and low cost successive ionic layer adsorption and reaction (SILAR) method on stainless steel (SS) substrate at room temperature. The formation of interconnected nanoparticles with nanoporous surface morphology has been achieved and which is favourable to the supercapacitor applications. Electrochemical supercapacitive performance of Bi2S3 thin film electrode has been performed through cyclic voltammetry, charge-discharge and stability studies in aqueous Na2SO4 electrolyte. The Bi2S3 thin film electrode exhibits the specific capacitance of 289 Fg-1 at 5 mVs-1 scan rate in 1 M Na2SO4 electrolyte.

Superconducting ceramics in the Bi1.5SrCaCu2O sub x system by melt quenching technique

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Deguire, Mark R.

1989-01-01

Bi sub 1.5 SrCaCu sub 2 O sub x has been prepared in the glassy state by rapid quenching of the melt. The kinetics of crystallization of various phases in the glass have been evaluated by a variable heating rate differential scanning calorimetry method. The formation various phases on thermal treatments of the glass has been investigated by powder X-ray diffraction and electrical resistivity measurements. Heating at 450 C formed Bi sub 2 Sr sub 2 CuO sub 6, which disappeared on further heating at 765 C, where Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8 formed. Prolonged heating at 845 C resulted in the formation of a small amount of a phase with T sub c onset of approx. 108 K, believed to be Bi sub 2 Sr sub 2 Ca sub 2 Cu sub 3 O sub 10. This specimen showed zero resistivity at 54 K. The glass ceramic approach could offer several advantages in the fabrication of the high-T sub c superconductors in desired practical shapes such as continuous fibers, wires, tapes, etc.

Bi2O3 nanoparticles encapsulated in surface mounted metal-organic framework thin films

NASA Astrophysics Data System (ADS)

Guo, Wei; Chen, Zhi; Yang, Chengwu; Neumann, Tobias; Kübel, Christian; Wenzel, Wolfgang; Welle, Alexander; Pfleging, Wilhelm; Shekhah, Osama; Wöll, Christof; Redel, Engelbert

2016-03-01

We describe a novel procedure to fabricate a recyclable hybrid-photocatalyst based on Bi2O3@HKUST-1 MOF porous thin films. Bi2O3 nanoparticles (NPs) were synthesized within HKUST-1 (or Cu3(BTC)2) surface-mounted metal-organic frame-works (SURMOFs) and characterized using X-ray diffraction (XRD), a quartz crystal microbalance (QCM) and transmission electron microscopy (TEM). The Bi2O3 semiconductor NPs (diameter 1-3 nm)/SURMOF heterostructures exhibit superior photo-efficiencies compared to NPs synthesized using conventional routes, as demonstrated via the photodegradation of the nuclear fast red (NFR) dye.We describe a novel procedure to fabricate a recyclable hybrid-photocatalyst based on Bi2O3@HKUST-1 MOF porous thin films. Bi2O3 nanoparticles (NPs) were synthesized within HKUST-1 (or Cu3(BTC)2) surface-mounted metal-organic frame-works (SURMOFs) and characterized using X-ray diffraction (XRD), a quartz crystal microbalance (QCM) and transmission electron microscopy (TEM). The Bi2O3 semiconductor NPs (diameter 1-3 nm)/SURMOF heterostructures exhibit superior photo-efficiencies compared to NPs synthesized using conventional routes, as demonstrated via the photodegradation of the nuclear fast red (NFR) dye. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00532b

Microwave-assisted Bi2Se3 nanoparticles using various organic solvents

NASA Astrophysics Data System (ADS)

Vijila, J. Joy Jeba; Mohanraj, K.; Henry, J.; Sivakumar, G.

2016-01-01

Microwave assisted Bi2Se3 nanoparticles were synthesized from five different solvents DMF, EG, EG + H2O, EDA + dil.HNO3 and N2H4 + H2O + Ethanol. The influence of solvents on purity of the compound was analysed by using X-ray diffraction patterns. The result indicates pure rhombohedral Bi2Se3 nanoparticles formed for N2H4 + H2O + Ethanol. The presence of vibrational bands in the range of 400-800 cm- 1 is confirmed the formation of Bi2Se3. The maximum optical absorption observed around 450 nm and the band gap values are found in the range of 1.5 eV-2.17 eV for all the solvents. The nanostructure of the Bi2Se3 particles change with solvents. From the experimental results, the solvent N2H4 + H2O + Ethanol produces pure nanosize Bi2Se3 particles under the microwave assisted method.

1D Bi2S3 nanorod/2D e-WS2 nanosheet heterojunction photocatalyst for enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Vattikuti, S. V. Prabhakar; Shim, Jaesool; Byon, Chan

2018-02-01

The development of high-activity, long-life, precious-metal-free photocatalysts for redox reactions in photoelectrochemical cells and fuel cells remains challenging. The synthesis of high-activity heterostructured photocatalysts is crucial for efficient energy conversion strategies. Herein, a novel photocatalyst based on 1D Bi2S3 nanorods self-assembled on 2D exfoliated tungsten disulfide (e-WS2) nanosheets has been developed for the degradation of methyl orange (MO) dye in aqueous solution. We demonstrate a novel and facile hydrothermal method for the synthesis of a Bi2S3 nanorod/e-WS2 nanosheet heterostructure. The photocatalytic properties of the heterostructure under visible light were investigated. Enhanced photocatalytic activity was attributed to the presence of strong surface active sites, as well as the specific morphology of the composite. We also observed the fast transfer of electron-hole pairs at the material interface. This work demonstrates a non-noble semiconductor photocatalyst for the degradation of pollutants and evolution of H2.

Favorable Concurrence of Static and Dynamic Phenomena at the Morphotropic Phase Boundary of x BiNi 0.5 Zr 0.5 O 3 - ( 1 - x ) PbTiO 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Datta, Kaustuv; Neder, Reinhard; Chen, J.

We demore » monstrate that the morphotropic phase boundary of the lead-free ferroelectric system x BiNi 0.5 Zr 0.5 O 3 - ( 1 - x ) PbTiO 3 (NBT-xBT) can be uniquely distinguished by a reduced polarizationstate along with a non-uniform attening of the local potential function of A- and B-site cationsof the perovskite-type structure. This establishes a robust structure-property connections based onthe atomic-level structural correlations which elucidates the long-standing question: why the MPBof NBT-xBT does not excel as much as Pb-based materials do; and further help to develop strategyin designing ecient lead-free ferroelectric systems.« less

Favorable Concurrence of Static and Dynamic Phenomena at the Morphotropic Phase Boundary of x BiNi 0.5 Zr 0.5 O 3 - ( 1 - x ) PbTiO 3

DOE PAGES

Datta, Kaustuv; Neder, Reinhard; Chen, J.; ...

2017-11-16

We demore » monstrate that the morphotropic phase boundary of the lead-free ferroelectric system x BiNi 0.5 Zr 0.5 O 3 - ( 1 - x ) PbTiO 3 (NBT-xBT) can be uniquely distinguished by a reduced polarizationstate along with a non-uniform attening of the local potential function of A- and B-site cationsof the perovskite-type structure. This establishes a robust structure-property connections based onthe atomic-level structural correlations which elucidates the long-standing question: why the MPBof NBT-xBT does not excel as much as Pb-based materials do; and further help to develop strategyin designing ecient lead-free ferroelectric systems.« less

Synthesis, structure, and characterization of two new bismuth(III) selenite/tellurite nitrates: [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}](NO{sub 3}) and [Bi(TeO{sub 3})](NO{sub 3})

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Chang-Yu; Wei, Ming-Fang; Geng, Lei, E-mail: lgeng.cn@gmail.com

Two new bismuth(III) selenite/tellurite nitrates, [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}](NO{sub 3}) and [Bi(TeO{sub 3})](NO{sub 3}), have been synthesized by conventional facile hydrothermal method at middle temperature 200 °C and characterized by single-crystal X-ray diffraction, powder diffraction, UV–vis–NIR optical absorption spectrum, infrared spectrum and thermal analylsis. Both [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}](NO{sub 3}) and [Bi(TeO3)](NO3) crystallize in the monoclinic centronsymmetric space group P2{sub 1}/c with a=9.9403(4) Å, b=9.6857(4) Å, c=10.6864(5) Å, β=93.1150(10)° for [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}](NO{sub 3}) and a=8.1489(3) Å, b=9.0663(4) Å, c=7.4729(3) Å, β=114.899(2)° for Bi(TeO3)(NO3), respectively. The two compounds, whose structures are composed of three different asymmetricmore » building units, exhibit two different types of structures. The structure of [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}](NO{sub 3}) features a three-dimensional (3D) bismuth(III) selenite cationic tunnel structure [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}] {sup 3}{sub ∞} with NO{sub 3}{sup −} anion group filling in the 1D tunnel along b axis. The structure of [Bi(TeO{sub 3})](NO{sub 3}) features 2D bismuth(III) tellurite [Bi(TeO{sub 3}){sub 2}]{sup 2}{sub ∞} layers separated by NO{sub 3}{sup −} anion groups. The results of optical diffuse-reflectance spectrum measurements and electronic structure calculations based on density functional theory methods show that the two compounds are wide band-gap semiconductors. - Graphical abstract: Two novel bismuth{sup III} selenite/tellurite nitrates [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}](NO{sub 3}) with 3D tunnel structure and [Bi(TeO{sub 3})](NO{sub 3}) with 2D layer structure have been firstly synthesized and characterized. Display Omitted - Highlights: • Two novel bismuth{sup III} nitrates [(Bi{sub 3}O{sub 2})(SeO{sub 3}){sub 2}](NO{sub 3}) and [Bi(TeO{sub 3})](NO{sub 3}) were

Magnetic interactions in BiFe0.5Mn0.5O3 films and BiFeO3/BiMnO3 superlattices

NASA Astrophysics Data System (ADS)

Xu, Qingyu; Sheng, Yan; Khalid, M.; Cao, Yanqiang; Wang, Yutian; Qiu, Xiangbiao; Zhang, Wen; He, Maocheng; Wang, Shuangbao; Zhou, Shengqiang; Li, Qi; Wu, Di; Zhai, Ya; Liu, Wenqing; Wang, Peng; Xu, Y. B.; Du, Jun

2015-03-01

The clear understanding of exchange interactions between magnetic ions in substituted BiFeO3 is the prerequisite for the comprehensive studies on magnetic properties. BiFe0.5Mn0.5O3 films and BiFeO3/BiMnO3 superlattices have been fabricated by pulsed laser deposition on (001) SrTiO3 substrates. Using piezoresponse force microscopy (PFM), the ferroelectricity at room temperature has been inferred from the observation of PFM hysteresis loops and electrical writing of ferroelectric domains for both samples. Spin glass behavior has been observed in both samples by temperature dependent magnetization curves and decay of thermo-remnant magnetization with time. The magnetic ordering has been studied by X-ray magnetic circular dichroism measurements, and Fe-O-Mn interaction has been confirmed to be antiferromagnetic (AF). The observed spin glass in BiFe0.5Mn0.5O3 films has been attributed to cluster spin glass due to Mn-rich ferromagnetic (FM) clusters in AF matrix, while spin glass in BiFeO3/BiMnO3 superlattices is due to competition between AF Fe-O-Fe, AF Fe-O-Mn and FM Mn-O-Mn interactions in the well ordered square lattice with two Fe ions in BiFeO3 layer and two Mn ions in BiMnO3 layer at interfaces.

ABCA1, ABCG1 and SR-BI: hormonal regulation in primary rat hepatocytes and human cell lines

PubMed Central

Sporstøl, Marita; Mousavi, Seyed Ali; Eskild, Winnie; Roos, Norbert; Berg, Trond

2007-01-01

Background Scavenger receptor type B class I (SR-BI), ABC transporter A1 (ABCA1) -and G1 (ABCG1) all play important roles in the reverse cholesterol transport. Reverse cholesterol transport is a mechanism whereby the body can eliminate excess cholesterol. Here, the regulation of SR-BI, ABCA1, and ABCG1 by dexamethasone (a synthetic glucocorticoid) and insulin were studied in order to gain more insight into the role of these two hormones in the cholesterol metabolism. Results By use of real time RT-PCR and Western blotting we examined the expression of our target genes. The results show that SR-BI, ABCA1 and ABCG1 mRNA expression increased in response to dexamethasone while insulin treatment reduced the expression in primary rat hepatocytes. The stimulatory effect of dexamethasone was reduced by the addition of the anti-glucocorticoid mifepristone. In HepG2 cells and THP-1 macrophages, however, the effect of dexamethasone was absent or inhibitory with no significant change in the presence of mifepristone. The latter observation may be a result of the low protein expression of glucocorticoid receptor (GR) in these cell lines. Conclusion Our results illustrates that insulin and glucocorticoids, two hormones crucial in the carbohydrate metabolism, also play an important role in the regulation of genes central in reverse cholesterol transport. We found a marked difference in mRNA expression between the primary cells and the two established cell lines when studying the effect of dexamethasone which may result from the varying expression levels of GR. PMID:17241464

ABCA1, ABCG1 and SR-BI: hormonal regulation in primary rat hepatocytes and human cell lines.

PubMed

Sporstøl, Marita; Mousavi, Seyed Ali; Eskild, Winnie; Roos, Norbert; Berg, Trond

2007-01-22

Scavenger receptor type B class I (SR-BI), ABC transporter A1 (ABCA1) -and G1 (ABCG1) all play important roles in the reverse cholesterol transport. Reverse cholesterol transport is a mechanism whereby the body can eliminate excess cholesterol. Here, the regulation of SR-BI, ABCA1, and ABCG1 by dexamethasone (a synthetic glucocorticoid) and insulin were studied in order to gain more insight into the role of these two hormones in the cholesterol metabolism. By use of real time RT-PCR and Western blotting we examined the expression of our target genes. The results show that SR-BI, ABCA1 and ABCG1 mRNA expression increased in response to dexamethasone while insulin treatment reduced the expression in primary rat hepatocytes. The stimulatory effect of dexamethasone was reduced by the addition of the anti-glucocorticoid mifepristone. In HepG2 cells and THP-1 macrophages, however, the effect of dexamethasone was absent or inhibitory with no significant change in the presence of mifepristone. The latter observation may be a result of the low protein expression of glucocorticoid receptor (GR) in these cell lines. Our results illustrates that insulin and glucocorticoids, two hormones crucial in the carbohydrate metabolism, also play an important role in the regulation of genes central in reverse cholesterol transport. We found a marked difference in mRNA expression between the primary cells and the two established cell lines when studying the effect of dexamethasone which may result from the varying expression levels of GR.

Role of alkali carbonate and salt in topochemical synthesis of K1/2Na1/2NbO3 and NaNbO3 templates

NASA Astrophysics Data System (ADS)

Lee, Jae-Seok; Jeon, Jae-Ho; Choi, Si-Young

2013-11-01

Since the properties of lead-free piezoelectric materials have thus far failed to meet those of lead-based materials, either chemical doping or morphological texturing should be employed to improve the piezoelectric properties of lead-free piezoelectric ceramics. The goal of this study was to synthesize plate-like K1/2Na1/2NbO3 and NaNbO3 particles, which are the most favorable templates for morphological texturing of K1/2Na1/2NbO3 ceramics. To achieve this goal, Bi2.5Na3.5Nb5O18 precursors in a plate-like shape were first synthesized and subsequently converted into K1/2Na1/2NbO3 or NaNbO3 particles that retain the morphology of Bi2.5Na3.5Nb5O18. In this study, we found that sodium or potassium carbonate does not play a major role in converting the Bi2.5Na3.5Nb5O18 precursor to K1/2Na1/2NbO3 or NaNbO3, on the contrary to previous reports; however, the salt contributes to the conversion reaction. All synthesis processes have been performed via a molten salt method, and scanning electron microscopy, scanning probe microscopy, and inductively coupled plasma mass spectroscopy were used to characterize the synthesized K1/2Na1/2NbO3 or NaNbO3 templates.

Anisotropic layered Bi2Te3-In2Te3 composites: control of interface density for tuning of thermoelectric properties

PubMed Central

Liu, Dongmei; Li, Xinzhong; Borlido, Pedro Miguel de Castro; Botti, Silvana; Schmechel, Roland; Rettenmayr, Markus

2017-01-01

Layered (Bi1−xInx)2Te3-In2Te3 (x = 0.075) composites of pronounced anisotropy in structure and thermoelectric properties were produced by zone melting and subsequent coherent precipitation of In2Te3 from a (Bi1−xInx)2Te3 (x > 0.075) matrix. Employing solid state phase transformation, the Bi2Te3/In2Te3 interface density was tuned by modifying the driving force for In2Te3 precipitation. The structure-property relationship in this strongly anisotropic material is characterized thoroughly and systematically for the first time. Unexpectedly, with increasing Bi2Te3/In2Te3 interface density, an increase in electrical conductivity and a decrease in the absolute Seebeck coefficient were found. This is likely to be due to electron accumulation layers at the Bi2Te3/In2Te3 interfaces and the interplay of bipolar transport in Bi2Te3. Significantly improved thermoelectric properties of Bi2Te3-In2Te3 composites as compared to the single phase (Bi1−xInx)2Te3 solid solution are obtained. PMID:28272541

Oxidation Studies of Cu12Sb3.9Bi0.1S10Se3 Tetrahedrite

NASA Astrophysics Data System (ADS)

Gonçalves, António P.; Lopes, Elsa B.; Montemor, Maria F.; Monnier, Judith; Lenoir, Bertrand

2018-02-01

Tetrahedrites are widespread minerals with general formula Cu10 M 2Sb4S13 (M = Cu, Mn, Fe, Co, Ni, Zn). Their thermoelectric properties can be tuned through proper doping and reach zT values as high as 1, being considered promising low-cost thermoelectric materials. However, for practical application in thermoelectric devices, it is necessary to establish their ability to operate for long periods under working temperatures and atmospheres. We present herein studies of oxidation in air of Cu12Sb3.9Bi0.1S10Se3 tetrahedrite at four different temperatures between 230°C and 375°C, together with preliminary corrosion studies in aggressive NaCl electrolyte. Surface oxidation already occurs at the lower studied temperatures, but a strong decrease of the oxidation rate is observed for materials treated at intermediate temperature (275°C), where a continuous surface layer of Cu2-x S forms, pointing to a protective effect of this layer that could be applied in devices operating at such temperatures. For the material treated at higher temperatures (350°C and 375°C), no tetrahedrite phases were seen after 1500 h, which can be related to the (tetrahedrite + chalcostibite + antimony → skinnerite) reaction that occurs above 280°C. Corrosion studies indicated that increasing the oxidation temperature unfortunately leads to a decrease of the corrosion resistance of tetrahedrite-based phases.

Structural Channels and Atomic-Cluster Insertion in CsxBi4Te6 (1 ≤ x ≤ 1.25) As Observed by Aberration-Corrected Scanning Transmission Electron Microscopy.

PubMed

Zhang, Ruixin; Yang, Huaixin; Guo, Cong; Tian, Huanfang; Shi, Honglong; Chen, Genfu; Li, Jianqi

2016-12-19

Microstructural analyses based on aberration-corrected scanning transmission electron microscopy (STEM) observations demonstrate that low-dimensional Cs x Bi 4 Te 6 materials, known to be a novel thermoelectric and superconducting system, contain notable structural channels that go directly along the b axis, which can be partially filled by atom clusters depending on the thermal treatment process. We successfully prepared two series of Cs x Bi 4 Te 6 single-crystalline samples using two different sintering processes. The Cs x Bi 4 Te 6 samples prepared using an air-quenching method show superconductivity at approximately 4 K, while the Cs x Bi 4 Te 6 with the same nominal compositions prepared by slowly cooling are nonsuperconductors. Moreover, atomic structural investigations of typical samples reveal that the structural channels are often empty in superconducting materials; thus, we can represent the superconducting phase as Cs 1-y Bi 4 Te 6 with considering the point defects in the Cs layers. In addition, the channels in the nonsuperconducting crystals are commonly partially occupied by triplet Bi clusters. Moreover, the average structures for these two phases are also different in their monoclinic angles (β), which are estimated to be 102.3° for superconductors and 100.5° for nonsuperconductors.

Ultraviolet and visible range plasmonics in the topological insulator Bi1.5Sb0.5Te1.8Se1.2

NASA Astrophysics Data System (ADS)

Ou, Jun-Yu; So, Jin-Kyu; Adamo, Giorgio; Sulaev, Azat; Wang, Lan; Zheludev, Nikolay I.

2014-10-01

The development of metamaterials, data processing circuits and sensors for the visible and ultraviolet parts of the spectrum is hampered by the lack of low-loss media supporting plasmonic excitations. This has driven the intense search for plasmonic materials beyond noble metals. Here we show that the semiconductor Bi1.5Sb0.5Te1.8Se1.2, also known as a topological insulator, is also a good plasmonic material in the blue-ultraviolet range, in addition to the already-investigated terahertz frequency range. Metamaterials fabricated from Bi1.5Sb0.5Te1.8Se1.2 show plasmonic resonances from 350 to 550 nm, while surface gratings exhibit cathodoluminescent peaks from 230 to 1,050 nm. The observed plasmonic response is attributed to the combination of bulk charge carriers from interband transitions and surface charge carriers of the topological insulator. The importance of our result is in the identification of new mechanisms of negative permittivity in semiconductors where visible range plasmonics can be directly integrated with electronics.

Human ABCB1 (P-glycoprotein) and ABCG2 mediate resistance to BI 2536, a potent and selective inhibitor of Polo-like kinase 1.

PubMed

Wu, Chung-Pu; Hsiao, Sung-Han; Sim, Hong-May; Luo, Shi-Yu; Tuo, Wei-Cherng; Cheng, Hsing-Wen; Li, Yan-Qing; Huang, Yang-Hui; Ambudkar, Suresh V

2013-10-01

The overexpression of the serine/threonine specific Polo-like kinase 1 (Plk1) has been detected in various types of cancer, and thus has fast become an attractive therapeutic target for cancer therapy. BI 2536 is the first selective inhibitor of Plk1 that inhibits cancer cell proliferation by promoting G2/M cell cycle arrest at nanomolar concentrations. Unfortunately, alike most chemotherapeutic agents, the development of acquired resistance to BI 2536 is prone to present a significant therapeutic challenge. One of the most common mechanisms for acquired resistance in cancer chemotherapy is associated with the overexpression of ATP-binding cassette (ABC) transporters ABCB1, ABCC1 and ABCG2. Here, we discovered that overexpressing of either ABCB1 or ABCG2 is a novel mechanism of acquired resistance to BI 2536 in human cancer cells. Moreover, BI 2536 stimulates the ATPase activity of both ABCB1 and ABCG2 in a concentration-dependent manner, and inhibits the drug substrate transport mediated by these transporters. More significantly, the reduced chemosensitivity and BI 2536-mediated G2/M cell cycle arrest in cancer cells overexpressing either ABCB1 or ABCG2 can be significantly restored in the presence of selective inhibitor or other chemotherapeutic agents that also interact with ABCB1 and ABCG2, such as tyrosine kinase inhibitors nilotinib and lapatinib. Taken together, our findings indicate that in order to circumvent ABCB1 or ABCG2-mediated acquired resistance to BI 2536, a combined regimen of BI 2536 and inhibitors or clinically active drugs that potently inhibit the function of ABC drug transporters, should be considered as a potential treatment strategy in the clinic. Copyright © 2013 Elsevier Inc. All rights reserved.

Dielectric and Impedance Characteristics of Nickel-Modified BiFeO3-BaTiO3 Electronic Compound

NASA Astrophysics Data System (ADS)

Das, S. N.; Pardhan, S. K.; Bhuyan, S.; Sahoo, S.; Choudhary, R. N. P.; Goswami, M. N.

2018-01-01

The temperature- and field-dependent capacitive, resistive and conducting characteristics of nickel-modified binary electronic systems of bismuth ferrite (BiFeO3) and barium titanate (BaTiO3) have been investigated using dielectric and impedance spectroscopy techniques. The orthorhombic crystal structures of the solid solution (Bi1-2xNixBax)(Fe1-2xTi0.2x)O3 (with x = 0.10, 0.15, 0.20 and 0.25) have been identified from powder x-ray crystallography. The micrographs exhibit the development of dense samples with reduced grain size for higher percentage of Ni in the BiFeO3-BaTiO3. The stoichiometric content of each sample has been realized using the energy dispersive x-ray technique. The relationship between micro-structural study and frequency-temperature-dependent electrical properties of the compound has revealed a negative temperature coefficient of resistance behavior. A non-Debye-type relaxation process is observed from the Niquist plot. The studied compound presents important dielectric properties for the formulation of electronic devices.

The effect of Bi composition on the properties of InP{sub 1−x}Bi{sub x} grown by liquid phase epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, T. D., E-mail: tddas@hotmail.com

InP{sub 1−x}Bi{sub x} epilayers (x ≥ 1.2%) on InP (001) are grown reproducibly by liquid phase epitaxy with conventional solution baking in a H{sub 2} environment. The Bi composition and surface morphology of the grown layers are studied by secondary ion mass spectroscopy and atomic force microscopy, respectively. High-resolution x-ray diffraction is used to characterize the lattice parameters and the crystalline quality of the layers. 10 K photoluminescence measurements indicate three clearly resolved peaks in undoped InP layers with band-to-band transition at 1.42 eV which is redshifted with Bi incorporation in the layer with a maximum band gap reduction of 50 meV/% Bi. The effectmore » is attributed to the interaction between the valence band edge and Bi-related defect states as is explained here by valence-band anticrossing model. Room temperature Hall measurements indicate that the mobility of the layer is not significantly affected for Bi concentration up to 1.2%.« less

CERES BiDirectional Scans (BDS) data in HDF (CER_BDS_Terra-FM1_Edition1)

NASA Technical Reports Server (NTRS)

Wielicki, Bruce A. (Principal Investigator)

Each BiDirectional Scans (BDS) data product contains twenty-four hours of Level-1b data for each CERES scanner instrument mounted on each spacecraft. The BDS includes samples taken in normal and short Earth scan elevation profiles in both fixed and rotating azimuth scan modes (including space, internal calibration, and solar calibration views). The BDS contains Level-0 raw (unconverted) science and instrument data as well as the geolocated converted science and instrument data. The BDS contains additional data not found in the Level-0 input file, including converted satellite position and velocity data, celestial data, converted digital status data, and parameters used in the radiance count conversion equations. The following CERES BDS data sets are currently available: CER_BDS_TRMM-PFM_Edition1 CER_BDS_Terra-FM1_Edition1 CER_BDS_Terra-FM2_Edition1 CER_BDS_Terra-FM1_Edition2 CER_BDS_Terra-FM2_Edition2 CER_BDS_Aqua-FM3_Edition1 CER_BDS_Aqua-FM4_Edition1 CER_BDS_Aqua-FM3_Edition2 CER_BDS_Aqua-FM4_Edition2 CER_BDS_Aqua-FM3_Edition1-CV CER_BDS_Aqua-FM4_Edition1-CV CER_BDS_Terra-FM1_Edition1-CV CER_BDS_Terra-FM2_Edition1-CV. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1997-12-27; Stop_Date=2005-11-02] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180] [Data_Resolution: Temporal_Resolution=1 day; Temporal_Resolution_Range=Daily - < Weekly].

Highly Enhanced Thermoelectric Properties of Bi/Bi2S3 Nanocomposites.

PubMed

Ge, Zhen-Hua; Qin, Peng; He, DongSheng; Chong, Xiaoyu; Feng, Dan; Ji, Yi-Hong; Feng, Jing; He, Jiaqing

2017-02-08

Bismuth sulfide (Bi 2 S 3 ) has been of high interest for thermoelectric applications due to the high abundance of sulfur on Earth. However, the low electrical conductivity of pristine Bi 2 S 3 results in a low figure of merit (ZT). In this work, Bi 2 S 3 @Bi core-shell nanowires with different Bi shell thicknesses were prepared by a hydrothermal method. The core-shell nanowires were densified to Bi/Bi 2 S 3 nanocomposite by spark plasma sintering (SPS), and the structure of the nanowire was maintained as the nanocomposite due to rapid SPS processing and low sintering temperature. The thermoelectric properties of bulk samples were investigated. The electrical conductivity of a bulk sample after sintering at 673 K for 5 min using Bi 2 S 3 @Bi nanowire powders prepared by treating Bi 2 S 3 nanowires in a hydrazine solution for 3 h is 3 orders of magnitude greater than that of a pristine Bi 2 S 3 sample. The nanocomposite possessed the highest ZT value of 0.36 at 623 K. This represents a new strategy for densifying core-shell powders to enhance their thermoelectric properties.

On atomic mechanisms governing the oxidation of Bi2Te3

NASA Astrophysics Data System (ADS)

Music, Denis; Chang, Keke; Schmidt, Paul; Braun, Felix N.; Heller, Martin; Hermsen, Steffen; Pöllmann, Peter J.; Schulzendorff, Till; Wagner, Cedric

2017-12-01

Oxidation of Bi2Te3 (space group R \\overline{3} m) has been investigated using experimental and theoretical means. Based on calorimetry, x-ray photoelectron spectroscopy and thermodynamic modelling, Bi2Te3 is at equilibrium with Bi2O3 and TeO2, whereby the most stable compound is Bi2Te3, followed by Bi2O3. The reactivity of Bi towards oxygen is expected to be higher than that of Te. This notion is supported by density functional theory. The strongest bond is formed between Bi and Te, followed by Bi-O. This gives rise to unanticipated atomic processes. Dissociatively adsorbed oxygen diffuses through Bi and Te basal planes of Bi2Te3(0 0 0 1) and preferably interacts with Bi. The Te termination considerably retards this process. These findings may clarify conflicting literature data. Any basal plane off-cut or Bi terminations trigger oxidation, but a perfect basal cleavage, where only Te terminations are exposed to air, may be stable for a longer period of time. These results are of relevance for applications in which surfaces are of key importance, such as nanostructured Bi2Te3 thermoelectric devices.

The new misfit compound (BiSe){sub 1.15}(TiSe{sub 2}){sub 2} and the role of dimensionality in the Cu{sub x}(BiSe){sub 1+δ}(TiSe{sub 2}){sub n} series

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trump, Benjamin A., E-mail: btrump1@jhu.edu; Department of Physics and Astronomy, Institute for Quantum Matter, Johns Hopkins University, Baltimore, MD 21218; Livi, Kenneth J.T.

The synthesis and physical properties of the new misfit compound (BiSe){sub 1.15}(TiSe{sub 2}){sub 2} are reported. Transmission electron microscopy and powder X-ray diffraction show that the structure consists of alternating rock-salt type BiSe layers and hexagonal (TiSe{sub 2}){sub 2} double layers. Resistivity, specific heat, and magnetization measurements show that it has metallic and diamagnetic behaviors. These results are interpreted and discussed in the context of the transition between single-layer (BiSe){sub 1.13}(TiSe{sub 2}), which shows no charge density wave, and infinite-layered (bulk) 1T-TiSe{sub 2}, which undergoes a charge density wave transition at T=202 K. Intercalation with copper, Cu{sub x}(BiSe){sub 1.15}(TiSe{sub 2}){submore » 2}, (0≤x≤0.10) is also reported, but unlike Cu{sub x}TiSe{sub 2}, no superconductivity is observed down to T=0.05 K. Thus, the series Cu{sub x}(BiSe){sub 1+δ}(TiSe{sub 2}){sub n} provides an effective approach to elucidate the impact of dimensionality on charge density wave formation and superconductivity. - Graphical abstract: The newly discovered misfit compound (BiSe){sub 1.15}(TiSe{sub 2}){sub 2} shown in the series (BiSe){sub 1+δ}(TiSe{sub 2}){sub n}. Display Omitted - Highlights: • Reports the structure and properties of the new misfit compound (BiSe){sub 1.15}(TiSe{sub 2}){sub 2}. • The structure consists of a rock salt type BiSe layer and a double (TiSe{sub 2}){sub 2} layer. • The n=1, 2 misfits (BiSe){sub 1+δ}(TiSe{sub 2}){sub n} are found not to exhibit CDW transitions. • Evidence is presented that there is likely a low-lying CDW excited state. • The series Cu{sub x}(BiSe){sub 1+δ}(TiSe{sub 2}){sub 2} does not superconduct, unlike Cu{sub x}TiSe{sub 2}.« less

Structural Transition and Electrical Properties of (1 - x)(Na0.4K0.1Bi0.5)TiO3- xSrTiO3 Lead-Free Piezoceramics

NASA Astrophysics Data System (ADS)

Liu, Xing; Zhai, Jiwei; Shen, Bo; Li, Feng; Li, Peng

2017-10-01

(1 - x)(Na0.4K0.1Bi0.5)TiO3- xSrTiO3 (NKBT- xST) ceramics with x = 0 mol.%, 3 mol.%, and 5 mol.% (0ST, 3ST, and 5ST) have been prepared by a conventional solid-state reaction method and their ferroelectric, electrostrictive, and pyroelectric properties investigated. Addition of ST considerably disrupted the long-range ferroelectric order of NKBT- xST ceramics, and the 5ST ceramic exhibited ergodic relaxor phase structure. T FR shifted to near or below room temperature for 5ST ceramic, accompanied by a significant decline of ferroelectricity and enhanced strain. As the temperature approached T FR, the NKBT- xST ceramics exhibited predominantly electrostrictive effect, and the 5ST ceramic presented relatively high electrostrictive coefficient Q 33 of 0.0193 m4/C2. High pyroelectric response was observed for 0ST, 3ST, and 5ST ceramics in the vicinity of T FR due to the large polarization release during the ferroelectric-relaxor structural transition. The 5ST ceramic exhibited high and frequency-insensitive (100 Hz to 10 kHz) room-temperature pyroelectric properties with pyroelectric coefficient p of 656 μC m-2 K-1 and figures of merit F i, F v, and F d reaching 233 pm/V, 0.013 m2/C, and 7.61 μPa-1/2, respectively, indicating that 5ST ceramic is a promising candidate to replace PZT-based ceramics.

Ab initio study of properties of BaBiO3 at high pressure

NASA Astrophysics Data System (ADS)

Martoňák, Roman; Ceresoli, Davide; Kagayama, Tomoko; Tosatti, Erio

BaBiO3 is a mixed-valence perovskite which escapes metallic state by creating a Bi-O bond disproportionation or CDW pattern, resulting in a Peierls semiconductor with gap of nearly 1 eV at zero pressure. Evolution of structural and electronic properties at high pressure is, however, largely unknown. Pressure, it might be natural to expect, could reduce the bond-disproportionation and bring the system closer to metalicity or even superconductivity. We address this question by ab initio DFT methods based on GGA and hybrid functionals in combination with crystal structure prediction techniques based on genetic algorithms. We analyze the pressure evolution of bond disproportionation as well as other order parameters related to octahedra rotation for various phases in connection with corresponding evolution of the electronic structure. Results indicate that BaBiO3 continues to resist metalization also under pressure, through structural phase transitions which sustain and in fact increase the diversity of length of Bi-O bonds for neighboring Bi ions, in agreement with preliminary high pressure resistivity data. R.M. Slovak Research and Development Agency Contract APVV-15-0496, VEGA project No. 1-0904-15; E.T. ERC MODPHYSFRICT Advanced Grant No. 320796.

Ferroelectric and structural instability in double perovskites Me1+Bi3+Me3+Nb5+O6 (Me1+ = Na, K, Rb; Me3+ = Sc, Ga, In, Lu)

NASA Astrophysics Data System (ADS)

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

2012-06-01

Within the Gordon-Kim generalized model with regard to the polarizabilities of ions, the lattice constants, the high-frequency permittivity, the Born dynamic charges, and the vibration constants of the crystal lattice are calculated for cation-ordered double perovskites Me1+Bi3+Me3+Nb5+O6. The vibration spectra of all the compounds exhibit two types of instabilities: instability associated with the rotation of the oxygen octahedron and ferroelectric instability. Various combinations of distortions with respect to the rotation mode yield five energetically most favorable distorted phases. The symmetry and the energy characteristics of these phases are discussed. In four of the five phases, the distortions associated with the oxygen octahedron rotation lead to polar phases, thus allowing one to speak of improper ferroelectricity in these compounds. One phase turns out to be nonpolar; however, it contains unstable polar modes such that a displacement along the eigenvectors of these modes gives rise to polarization in the crystal.

On atomic mechanisms governing the oxidation of Bi2Te3.

PubMed

Music, Denis; Chang, Keke; Schmidt, Paul; Braun, Felix N; Heller, Martin; Hermsen, Steffen; Pöllmann, Peter J; Schulzendorff, Till; Wagner, Cedric

2017-11-09

Oxidation of Bi 2 Te 3 (space group R [Formula: see text] m) has been investigated using experimental and theoretical means. Based on calorimetry, x-ray photoelectron spectroscopy and thermodynamic modelling, Bi 2 Te 3 is at equilibrium with Bi 2 O 3 and TeO 2 , whereby the most stable compound is Bi 2 Te 3 , followed by Bi 2 O 3 . The reactivity of Bi towards oxygen is expected to be higher than that of Te. This notion is supported by density functional theory. The strongest bond is formed between Bi and Te, followed by Bi-O. This gives rise to unanticipated atomic processes. Dissociatively adsorbed oxygen diffuses through Bi and Te basal planes of Bi 2 Te 3 (0 0 0 1) and preferably interacts with Bi. The Te termination considerably retards this process. These findings may clarify conflicting literature data. Any basal plane off-cut or Bi terminations trigger oxidation, but a perfect basal cleavage, where only Te terminations are exposed to air, may be stable for a longer period of time. These results are of relevance for applications in which surfaces are of key importance, such as nanostructured Bi 2 Te 3 thermoelectric devices.

Positron annihilation studies of Bi 2CaSr 2Cu 2O x and Bi 1.6Pb 0.4Ca 2Sr 2Cu 3O y in the region of the superconducting transition

NASA Astrophysics Data System (ADS)

Pujari, P. K.; Datta, T.; Manohar, S. B.; Prakash, Satya; Sastry, P. V. P. S. S.; Yakhmi, J. V.; Iyer, R. M.

1990-03-01

Doppler broadened annihilation radiation (DBAR) spectral parameters have been reported- for the first time- between 77 K and 300 K, for several Bi-based oxide superconductors, viz. A: single phase (2122) Bi 2CaSr 2Cu 2O x with Tc=85 K (R=0), B: a mixed phase lead doped sample containing both 2122 and 2223 with a nominal composition Bi 1.6Pb 0.4Ca 2Sr 2Cu 3O y, and, C: another 2122+2223 sample with same nominal composition as that of B but synthesised under a different heat-treatment schedule so as to yield a Tc=85 K (R=0). Analyses of these spectra using PAACFIT program yielded two components, of which the intensity of the narrow component, I N, and, the width of the broad component, T B, were seen to be the only temperature dependent parameters. At the onset of superconducting transition both T B and I N were seen to increase to a maximum value and decrease on further cooling. A double peak structure in T B vs temperature profile were observed in sample B and C, similar to one reported by us in Tl-Ca-Ba-Cu-O systems. In addition, presence of a magnetic field (1 KG) yielded no significant change in the DBAR spectral parameters. The results are discussed.

Correlation of the superconducting transition to oxygen stoichiometry in single-crystal Ba1-xKxBiO3-y

NASA Astrophysics Data System (ADS)

Mosley, W. D.; Dykes, J. W.; Klavins, P.; Shelton, R. N.; Sterne, P. A.; Howell, R. H.

1993-07-01

Temperature-dependent positron-lifetime experiments have been performed from room temperature to 15 K on single crystals of the oxide superconductor Ba1-xKxBiO3-y. Results indicate that the filling of oxygen vacancies has a marked impact on the superconducting properties of this system. Cation defect concentrations were below the detectable limit of positron-annihilation-analysis techniques in this material, which is in sharp contrast to identical studies on polycrystalline samples. We find that the positron lifetime in these electrochemically deposited single crystals is determined by the oxygen stoichiometry of the lattice, but there is no experimental signature of strong positron localization. By performing a subsequent oxygen anneal on the crystals, the superconducting transition is sharpened and the onset is raised. The observed change in positron lifetime associated with this annealing procedure is in quantitative agreement with theory.

Study on the site preference of Ca in superconducting oxides Bi{sub 2}Sr{sub 2−x}Ca{sub x}CuO{sub 6+δ} (0.1 ≤ x ≤ 1.0)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, B.Z.; Zhou, S.L.; Wang, H.

2014-01-15

A series of compound with the nominal composition of Bi{sub 2}Sr{sub 2−x}Ca{sub x}CuO{sub 6+δ} (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0) were synthesized by the sol–gel method. Constituent phases and crystal structure of samples were analyzed by X-ray diffraction. It can be found that the Ca-doped Bi-2201 system was composed of Bi-2201 phase containing Ca and a small quantity of Bi{sub 16}(Sr,Ca){sub 14}O{sub 38}. For Bi-2201 unit cell containing Ca, chemical component and site preference of Ca atoms were characterized systematically by transmission electron microscopy. With the introduction of Ca atoms, Sr-sites have been occupiedmore » partially by Ca{sup 2+} in Bi-2201 unit cell, which leads to a decrease in the lattice parameters c and b of the Bi-2201 phase when the Ca-content x is below 0.6. Two types of new orthorhombic lattices are formed in the substitution. One is a lattice with space group Pma2 as the two nearest neighbor Sr-sites in the same Sr–O layer are occupied by Ca{sup 2+}. Its lattice parameters can be characterized as a = 5.402 Å, b = 5.313 Å and c = 24.272 Å, respectively. When two nearest Sr ions of the second neighboring Sr–O layers are replaced by Ca{sup 2+} ions, the lattice with the space group Pmn2{sub 1} can be formed. Its lattice parameters are close to that of the previous. The modulation vector is lying in the a*–c* plane in the two new orthorhombic lattices (Pma2 and Pmn2{sub 1}). Bi/Ca-2201 lattice (with Ca) and Bi-2201 lattice (without Ca) coexist in the same Bi{sub 2}Sr{sub 2−x}Ca{sub x}CuO{sub 6}+{sub δ} grain, which can be described as an intergrowth structure.« less

High-power Femtosecond Optical Parametric Amplification at 1 kHz in BiB(3)O(6) pumped at 800 nm.

PubMed

Petrov, Valentin; Noack, Frank; Tzankov, Pancho; Ghotbi, Masood; Ebrahim-Zadeh, Majid; Nikolov, Ivailo; Buchvarov, Ivan

2007-01-22

Substantial power scaling of a travelling-wave femtosecond optical parametric amplifier, pumped near 800 nm by a 1 kHz Ti:sapphire laser amplifier, is demonstrated using monoclinic BiB(3)O(6) in a two stage scheme with continuum seeding. Total energy output (signal plus idler) exceeding 1 mJ is achieved, corresponding to an intrinsic conversion efficiency of approximately 32% for the second stage. The tunability extends from 1.1 to 2.9 microm. The high parametric gain and broad amplification bandwidth of this crystal allowed the maintenance of the pump pulse duration, leading to pulse lengths less than 140 fs, both for the signal and idler pulses, even at such high output levels.

Band gap modulation in magnetically doped low-defect thin films of (Bi1-xSbx)2 Te3 with minimized bulk carrier concentration

NASA Astrophysics Data System (ADS)

Maximenko, Yulia; Scipioni, Kane; Wang, Zhenyu; Katmis, Ferhat; Steiner, Charles; Weis, Adam; van Harlingen, Dale; Madhavan, Vidya

Topological insulators Bi2Te3 and Sb2Te3 are promising materials for electronics, but both are naturally prone to vacancies and anti-site defects that move the Fermi energy onto the bulk bands. Fabricating (Bi1-xSbx)2 Te3 (BST) with the tuned x minimizes point defects and unmasks topological surface states by reducing bulk carriers. BST thin films have shown topological surface states and quantum anomalous Hall effect. However, different studies reported variable Sb:Bi ratios used to grow an undoped BST film. Here, we develop a reliable way to grow defect-free subnanometer-flat BST thin films having the Fermi energy tuned to the Dirac point. High-resolution scanning tunneling microscopy (STM) and Landau level spectroscopy prove the importance of crystallinity and surface roughness-not only Sb:Bi ratio-for the final bulk carrier concentration. The BST thin films were doped with Cr and studied with STM with atomic resolution. Counterintuitively, Cr density is anticorrelated with the local band gap due to Cr's antiferromagnetic order. We analyze the correlations and report the relevant band gap values. Predictably, high external magnetic field compromises antiferromagnetic order, and the local band gap increases. US DOE DE-SC0014335; Moore Found. GBMF4860; F. Seitz MRL.

Property Characterization and Photocatalytic Activity Evaluation of BiGdO3 Nanoparticles under Visible Light Irradiation

PubMed Central

Luan, Jingfei; Shen, Yue; Zhang, Lingyan; Guo, Ningbin

2016-01-01

BiGdO3 nanoparticles were prepared by a solid-state reaction method and applied in photocatalytic degradation of dyes in this study. BiGdO3 was characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, UV-Vis diffuse reflectance spectroscopy and transmission electron microscopy. The results showed that BiGdO3 crystallized well with the fluorite-type structure, a face-centered cubic crystal system and a space group Fm3m 225. The lattice parameter of BiGdO3 was 5.465 angstrom. The band gap of BiGdO3 was estimated to be 2.25 eV. BiGdO3 showed a strong optical absorption during the visible light region. Moreover, the photocatalytic activity of BiGdO3 was evaluated by photocatalytic degradation of direct dyes in aqueous solution under visible light irradiation. BiGdO3 demonstrated excellent photocatalytic activity in degrading Direct Orange 26 (DO-26) or Direct Red 23 (DR-23) under visible light irradiation. The photocatalytic degradation of DO-26 or DR-23 followed the first-order reaction kinetics, and the first-order rate constant was 0.0046 or 0.0023 min−1 with BiGdO3 as catalyst. The degradation intermediates of DO-26 were observed and the possible photocatalytic degradation pathway of DO-26 under visible light irradiation was provided. The effect of various operational parameters on the photocatalytic activity and the stability of BiGdO3 particles were also discussed in detail. BiGdO3/(visible light) photocatalysis system was confirmed to be suitable for textile industry wastewater treatment. PMID:27618018

Kinetically Controlled Formation and Decomposition of Metastable [(BiSe) 1+δ] m[TiSe 2] m Compounds

DOE PAGES

Lygo, Alexander C.; Hamann, Danielle M.; Moore, Daniel B.; ...

2018-02-12

We report that preparing homologous series of compounds allows chemists to rapidly discover new compounds with predictable structure and properties. Synthesizing compounds within such a series involves navigating a free energy landscape defined by the interactions within and between constituent atoms. Historically, synthesis approaches are typically limited to forming only the most thermodynamically stable compound under the reaction conditions. Presented here is the synthesis, via self-assembly of designed precursors, of isocompositional incommensurate layered compounds [(BiSe) 1+δ] m[TiSe 2] m with m = 1, 2, and 3. The structure of the BiSe bilayer in the m = 1 compound is notmore » that of the binary compound, and this is the first example of compounds where a BiSe layer thicker than a bilayer in heterostructures has been prepared. Specular and in-plane X-ray diffraction combined with high-resolution electron microscopy data was used to follow the formation of the compounds during low-temperature annealing and the subsequent decomposition of the m = 2 and 3 compounds into [(BiSe) 1+δ]1[TiSe 2] 1 at elevated temperatures. These results show that the structure of the precursor can be used to control reaction kinetics, enabling the synthesis of kinetically stable compounds that are not accessible via traditional techniques. Lastly, the data collected as a function of temperature and time enabled us to schematically construct the topology of the free energy landscape about the local free energy minima for each of the products.« less

Kinetically Controlled Formation and Decomposition of Metastable [(BiSe) 1+δ] m[TiSe 2] m Compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lygo, Alexander C.; Hamann, Danielle M.; Moore, Daniel B.

We report that preparing homologous series of compounds allows chemists to rapidly discover new compounds with predictable structure and properties. Synthesizing compounds within such a series involves navigating a free energy landscape defined by the interactions within and between constituent atoms. Historically, synthesis approaches are typically limited to forming only the most thermodynamically stable compound under the reaction conditions. Presented here is the synthesis, via self-assembly of designed precursors, of isocompositional incommensurate layered compounds [(BiSe) 1+δ] m[TiSe 2] m with m = 1, 2, and 3. The structure of the BiSe bilayer in the m = 1 compound is notmore » that of the binary compound, and this is the first example of compounds where a BiSe layer thicker than a bilayer in heterostructures has been prepared. Specular and in-plane X-ray diffraction combined with high-resolution electron microscopy data was used to follow the formation of the compounds during low-temperature annealing and the subsequent decomposition of the m = 2 and 3 compounds into [(BiSe) 1+δ]1[TiSe 2] 1 at elevated temperatures. These results show that the structure of the precursor can be used to control reaction kinetics, enabling the synthesis of kinetically stable compounds that are not accessible via traditional techniques. Lastly, the data collected as a function of temperature and time enabled us to schematically construct the topology of the free energy landscape about the local free energy minima for each of the products.« less

A Highly Efficient UV-Vis-NIR Active Ln(3+)-Doped BiPO4/BiVO4 Nanocomposite for Photocatalysis Application.

PubMed

Ganguli, Sagar; Hazra, Chanchal; Chatti, Manjunath; Samanta, Tuhin; Mahalingam, Venkataramanan

2016-01-12

In this Article, we report the synthesis of Ln(3+) (Yb(3+), Tm(3+))-doped BiPO4/BiVO4 nanocomposite photocatalyst that shows efficient photocatalytic activity under UV-visible-near-infrared (UV-vis-NIR) illumination. Incorporation of upconverting Ln(3+) ion pairs in BiPO4 nanocrystals resulted in strong emission in the visible region upon excitation with a NIR laser (980 nm). A composite of BiPO4 nanocrystals and vanadate was prepared by the addition of vanadate source to BiPO4 nanocrystals. In the nanocomposite, the strong blue emission from Tm(3+) ions via upconversion is nonradiatively transferred to BiVO4, resulting in the production of excitons. This in turn generates reactive oxygen species and efficiently degrades methylene blue dye in aqueous medium. The nanocomposite also shows high photocatalytic activity both under the visible region (0.010 min(-1)) and under the full solar spectrum (0.047 min(-1)). The results suggest that the photocatalytic activity of the nanocomposite under both NIR as well as full solar irradiation is better compared to other reported nanocomposite photocatalysts. The choice of BiPO4 as the matrix for Ln(3+) ions has been discussed in detail, as it plays an important role in the superior NIR photocatalytic activity of the nanocomposite photocatalyst.