Single crystal growth of beta-Al2O3 for iso-index filters

NASA Astrophysics Data System (ADS)

Belt, R. F.; Randles, M. H.; Creamer, J. E.

1992-03-01

Single crystals of Beta-Al2O3 with a nominal composition of Na2O.11 Al2O3 were grown from stoichiometric melts contained in an iridium crucible. Seeding was achieved from an Al2O3 single crystal. The growth axis was along a, and x-ray data confirmed the unit cell parameters of a = 5.595 A and c = 22.531 A. The top and bottom lattice constants of the boules were equal to + 0.002 A and indicated a fairly uniform composition. The measured density was 3.25 g/cc. The boules remained physically intact with no major cracks. However, some cleavage progressed on the basal planes as determined by the appearance of interference fringes. Water vapor and CO2 did not enhance the cracking. Crystals were stored in a desiccator but continued to cleave. Ionic diffusions of Na(+), Ag(+), Pb(2+), Rb(+), Ca(2+), Cd(2+), and Tl(+) were performed by immersion of beta-Al2O3 into nitrate or chloride melts at temperatures of 360-7400 C.

COEXISTENCE OF DIFFERENT TYPES OF TRANSVERSE CONDUCTIVITY IN Y1-xPrxBa2Cu3 O7-δ SINGLE CRYSTALS WITH DIFFERENT PRASEODYMIUM CONCENTRATIONS

NASA Astrophysics Data System (ADS)

Vovk, R. V.; Vovk, N. R.; Goulatis, I. L.; Chroneos, A.

2013-10-01

In this paper, the influence of praseodymium doping on the conductivity across (transverse) the basal plane of high-temperature superconducting Y1-xPrxBa2Cu3O7-δ single crystals is investigated. It is determined that an increase of praseodymium doping leads to increased localization effects and the implementation of a metal-insulator transition Y1-xPrxBa2Cu3O7-δ, which always precedes the superconducting transition. The increase of the praseodymium concentration also leads to a significant displacement of the point of the metal-insulator transition to the low temperature region.

Continuous-wave and Q-switched microchip laser performance of Yb:Y3Sc2Al3O12 crystals.

PubMed

Dong, Jun; Ueda, Ken-ichi; Kaminskii, Alexander A

2008-04-14

Optical properties of Yb:Y(3)Sc(2)Al(3)O(12) crystal were investigated and compared with those from Yb:YAG crystals. The broad absorption and emission spectra of Yb:Y(3)Sc(2)Al(3)O(12) show that this crystal is very suitable for laser-diode pumping and ultrafast laser pulse generation. Laser-diode pumped continuous-wave and passively Q-switched Yb:Y(3)Sc(2)Al(3)O(12) lasers with Cr(4+):YAG crystals as saturable absorber have been demonstrated for the first time. Continuous-wave output power of 1.12 W around 1032 nm (multi-longitudinal modes) was measured with an optical-to-optical efficiency of 30%. Laser pulses with pulse energy of over 31 microJ and pulse width of 2.5 ns were measured at repetition rate of over 12.7 kHz; a corresponding peak power of over 12 kW was obtained. The longitudinal mode selection by a thin plate of Cr(4+):YAG as an intracavity etalon was also observed in passively Q-switched Yb:Y(3)Sc(2)Al(2)O(12) microchip lasers.

Bulk Crystallization in a SiO2/Al2O3/Y2O3/AlF3/B2O3/Na2O Glass: Fivefold Pseudo Symmetry due to Monoclinic Growth in a Glassy Matrix Containing Growth Barriers

PubMed Central

Wisniewski, Wolfgang; Seyring, Martin; Patzig, Christian; Höche, Thomas; Keshavarzi, Ashkan; Rüssel, Christian

2016-01-01

A glass with the mol% composition 17 Y2O3·33 Al2O3·40 SiO2·2 AlF3·3 Na2O·2 CeF3·3 B2O3 is heat treated at 1000 °C for 6–24 h. This results in the surface nucleation and growth of YAG. Nucleation and growth of star-shaped alumina and later of monoclinic β-Y2Si2O7 and orthorhombic δ-Y2Si2O7 are additionally observed in the bulk. Phase identification and localization are performed by electron backscatter diffraction (EBSD) as well as TEM analysis. The monoclinic β-Y2Si2O7 observed in the bulk occurs in the form of large, crystal agglomerates which range from 50 to 120 μm in size. The individual crystals are aligned along the c-axis which is the fastest growing axis. Ten probability maxima are observed in the pole-figures illustrating the rotation of orientations around the c-axes indicating a fivefold symmetry. This symmetry is caused by multiple twinning which results in a high probability of specific orientation relationships with rotation angles of ~36°, ~108° (also referred to as the pentagon angle) and ~144° around the c-axis. All these rotation angles are close to the multiples of 36° which are required for an ideal fivefold symmetry. This is the first report of a fivefold symmetry triggered by the presence of barriers hindering crystal growth. PMID:26813152

Czochralski growth of 2 in. Ca3Ta(Ga,Al)3Si2O14 single crystals for piezoelectric applications

NASA Astrophysics Data System (ADS)

Yoshikawa, Akira; Shoji, Yasuhiro; Ohashi, Yuji; Yokota, Yuui; Chani, Valery I.; Kitahara, Masanori; Kudo, Tetsuo; Kamada, Kei; Kurosawa, Shunsuke; Medvedev, Andrey; Kochurikhin, Vladimir

2016-10-01

Growth of 2-in. diameter Al-substituted Ca3TaGa3Si2O14 crystals by Czochralski method is reported. The crystals were grown from the melt of Ca3TaGa1.5Al1.5Si2O14 composition and had langasite structure. No inclusions of secondary phases were detected in these crystals. The Ca3Ta(Ga,Al)3Si2O14 mixed crystals produced using non-substituted Ca3TaGa3Si2O14 seeds were defective. They had cracks and/or poly-crystalline structure. However, those grown on the seed of approximately Ca3TaGa1.5Al1.5Si2O14 composition were defect-free. Phase diagram of the Ca3TaGa3Si2O14-Ca3TaAl3Si2O14 pseudo-binary system and segregation phenomenon are discussed in some details. Homogeneity of the crystals was evaluated by measuring 2D-mapping of leaky surface acoustic wave (LSAW) velocities for Y-cut Ca3TaGa1.5Al1.5Si2O14 substrate. Although some inhomogeneities were observed due to slight variations in chemical composition, the crystal had acceptable homogeneity for applications in acoustic wave devices exhibiting the LSAW velocity variation within ±0.048%.

Influence of Y2O3 Addition on Crystallization, Thermal, Mechanical, and Electrical Properties of BaO-Al2O3-B2O3-SiO2 Glass-Ceramic for Ceramic Ball Grid Array Package

NASA Astrophysics Data System (ADS)

Li, Bo; Li, Wei; Zheng, Jingguo

2018-01-01

Y2O3 addition has a significant influence on the crystallization, thermal, mechanical, and electrical properties of BaO -Al2O3 -B2O3 -SiO2 (BABS) glass-ceramics. Semi-quantitative calculation based on x-ray diffraction demonstrated that with increasing Y2O3 content, both the crystallinity and the phase content of cristobalite gradually decreased. It is effective for the additive Y2O3 to inhibit the formation of cristobalite phase with a large coefficient of thermal expansion value. The flexural strength and the Young's modulus, thus, are remarkably increased from 140 MPa to 200 MPa and 56.5 GPa to 63.7 GPa, respectively. Also, the sintering kinetics of BABS glass-ceramics with various Y2O3 were investigated using the isothermal sintering shrinkage curve at different sintering temperatures. The sintering activation energy Q sharply decreased from 99.8 kJ/mol to 81.5 kJ/mol when 0.2% Y2O3 was added, which indicated that a small amount of Y2O3 could effectively promote the sintering procedure of BABS glass-ceramics.

Linear electro-optic properties of relaxor-based ferroelectric 0.24Pb(In1/2Nb1/2)O3-(0.76 − x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystals

PubMed Central

Wu, Fengmin; Yang, Bin; Sun, Enwei; Liu, Gang; Tian, Hao; Cao, Wenwu

2013-01-01

Linear electro-optic properties of 0.24Pb(In1/2Nb1/2)O3-(0.76 − x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystals, with compositions in the rhombohedral, morphotropic phase boundary (MPB) and tetragonal phases, have been investigated. Very large effective electro-optic coefficient γc (204 pm/V) was observed in a crystal with the MPB composition when it is poled along [001]. The rhombohedral phase (x = 0.27 and 0.30) single crystals poled along [111] direction and tetragonal phase (x = 0.39) single crystal poled along [001] direction are in single domain, and their electro-optic coefficients (γc = 76, 94, and 43 pm/V for the crystals with x = 0.27, 0.30, and 0.39, respectively) were found to be much higher than that of traditional electro-optic single crystal LiNbO3 (γc = 19.9 pm/V). The electro-optic coefficients of the single crystal in the rhombohedral phase have excellent temperature stability in the experimental temperature range of 10–40 °C. The half-wave voltage Vπ was calculated to be much lower (less than 1000 V) than that of LiNbO3 single crystal (2800 V). These superior properties make the ternary relaxor-PT single crystals very promising for electro-optic modulation applications. PMID:23922449

Simultaneous presence of (Si{sub 3}O{sub 10}){sup 8−} and (Si{sub 2}O{sub 7}){sup 6−} groups in new synthetic mixed sorosilicates: BaY{sub 4}(Si{sub 2}O{sub 7})(Si{sub 3}O{sub 10}) and isotypic compounds, studied by single-crystal X-ray diffraction, Raman spectroscopy and DFT calculations

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

Wierzbicka-Wieczorek, Maria, E-mail: maria.wierzbicka-wieczorek@uni-jena.de; Többens, Daniel M.; Kolitsch, Uwe

2013-11-15

Three new, isotypic silicate compounds, BaY{sub 4}(Si{sub 2}O{sub 7})(Si{sub 3}O{sub 10}), SrYb{sub 4}(Si{sub 2}O{sub 7})(Si{sub 3}O{sub 10}) and SrSc{sub 4}(Si{sub 2}O{sub 7})(Si{sub 3}O{sub 10}), were synthesized using high-temperature flux growth techniques, and their crystal structures were solved from single-crystal X-ray intensity data: monoclinic, P2{sub 1}/m, with a=5.532(1)/5.469(1)/5.278(1), b=19.734(4)/19.447(4)/19.221(4), c=6.868(1)/6.785(1)/6.562(1) Å, β=106.53(3)/106.20(3)/106.50(3)°, V=718.8(2)/693.0(2)/638.3(2) Å{sup 3}, R(F)=0.0225/0.0204/0.0270, respectively. The topology of the novel structure type contains isolated horseshoe-shaped Si{sub 3}O{sub 10} groups (Si–Si–Si=93.15–95.98°), Si{sub 2}O{sub 7} groups (Si–O{sub bridge}–Si=180°, symmetry-restricted) and edge-sharing M(1)O{sub 6} and M(2)O{sub 6} octahedra. Single-crystal Raman spectra of the title compounds were measured and compared with Raman spectroscopicmore » data of chemically and topologically related disilicates and trisilicates, including BaY{sub 2}(Si{sub 3}O{sub 10}) and SrY{sub 2}(Si{sub 3}O{sub 10}). The band assignments are supported by additional theoretical calculation of Raman vibrations by DFT methods. - Graphical abstract: View of BaY{sub 4}(Si{sub 2}O{sub 7})(Si{sub 3}O{sub 10}) along [100], showing zigzag chains and the tri- and disilicate groups. The unit cell is outlined. Display Omitted - Highlights: • We report a novel interesting crystal structure type for mixed sorosilicates containing Y, Yb, and Sc. • Synthesis of such mixed sorosilicates is possible by a high-temperature flux-growth technique. • Calculation of Raman vibrations by advanced DFT methods allows a considerably improved interpretation of measured Raman spectra.« less

Spectroscopic and laser cooling results on Yb3+-doped BaY2F8 single crystal

NASA Astrophysics Data System (ADS)

Bigotta, Stefano; Parisi, Daniela; Bonelli, Lucia; Toncelli, Alessandra; Tonelli, Mauro; Di Lieto, Alberto

2006-07-01

Anti-Stokes cooling has been observed in an Yb3+-doped BaY2F8 single crystal. Single crystals have been grown by the Czochralski technique. The absorption spectra and the emission properties have been measured at room temperature and at 10K. The energy positions of the Stark sublevels of the ground and the excited state manifolds have been determined and separated from the vibronic substructure. The intrinsic decay time of the F5/22 level has been measured taking care of avoiding the effect of multiple reabsorption processes. The theoretical and experimental cooling efficiencies of Yb:BaY2F8 are evaluated and compared with respect to those of the most frequently investigated materials for laser cooling. A temperature drop of almost 4K was measured by pumping the crystal with 3W of laser radiation at ˜1025nm in single pass configuration with a cooling efficiency of ˜3%.

Magnetostriction of Hexagonal HoMnO3 and YMnO3 Single Crystals

NASA Astrophysics Data System (ADS)

Pavlovskii, N. S.; Dubrovskii, A. A.; Nikitin, S. E.; Semenov, S. V.; Terent'ev, K. Yu.; Shaikhutdinov, K. A.

2018-03-01

We report on the magnetostriction of hexagonal HoMnO3 and YMnO3 single crystals in a wide range of applied magnetic fields (up to H = 14 T) at all possible combinations of the mutual orientations of magnetic field H and magnetostriction Δ L/L. The measured Δ L/L( H, T) data agree well with the magnetic phase diagram of the HoMnO3 single crystal reported previously by other authors. It is shown that the nonmonotonic behavior of magnetostriction of the HoMnO3 crystal is caused by the Ho3+ ion; the magnetic moment of the Mn3+ ion parallel to the hexagonal crystal axis. The anomalies established from the magnetostriction measurements of HoMnO3 are consistent with the phase diagram of these compounds. For the isostructural YMnO3 single crystal with a nonmagnetic rare-earth ion, the Δ L/L( H, T) dependences are described well by a conventional quadratic law in a wide temperature range (4-100 K). In addition, the magnetostriction effect is qualitatively estimated with regard to the effect of the crystal electric field on the holmium ion.

HABIT CHANGES OF Y3Al5O12 AND Y3Ga5O12 GROWN FROM A PbO-PbF2 FLUX,

DTIC Science & Technology

Al2O3 or - Ga2O3 ratio in the melt. Y3Ga5O12 crystals have a pure (211) habit when grown from either a Y2O3- or PbO-rich melt. The crystals develop...small (110) faces when grown from a Ga2O3 - or PbF2-rich melt. Y3Al5O12 crystals have a pure (110) when grown from either a PbF2- or Al2O3-rich melt... Ga2O3 -rich melts. It is believed that the habit variations are caused by changes in either the surface diffusion or step propagation, due to Pb

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

PubMed

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

2016-03-01

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

Chalcogen (O2, S, Se, Te) atmosphere annealing induced bulk superconductivity in Fe1+yTe1-xSex single crystal

NASA Astrophysics Data System (ADS)

Sun, Y.; Tsuchiya, Y.; Yamada, T.; Taen, T.; Pyon, S.; Shi, Z. X.; Tamegai, T.

2014-09-01

We reported a detailed study of Fe1+yTe0.6Se0.4 single crystals annealed in the atmosphere of chalcogens (O2, S, Se, Te). After annealing with appropriate amount of chalcogens, Fe1+yTe0.6Se0.4 single crystals show Tc higher than 14 K with a sharp transition width ∼1 K. Critical current density Jc for the annealed crystals reach a very high value ∼2-4 × 105 A/cm2 under zero field, and is also robust under applied field at low temperatures. Magneto-optical imaging reveal that the Jc is homogeneously distributed in the annealed crystals and isotropic in the ab-plane. Our results show that annealing in the atmosphere of chalcogens can successfully induce bulk superconductivity in Fe1+yTe0.6Se0.4.

The atomic arrangement of iimoriite-(Y), Y2(SiO4)(CO3)

USGS Publications Warehouse

Hughes, J.M.; Foord, E.E.; Jai-Nhuknan, J.; Bell, J.M.

1996-01-01

Iimoriite-(Y) from Bokan Mountain, Prince of Wales Island, Alaska has been studied using single-crystal X-ray-diffraction techniques. The mineral, ideally Y2(SiO4)(CO3), crystallizes in space group P1, with a 6.5495(13), b 6.6291(14), c 6.4395(11)A??, ?? 116.364(15), ?? 92.556(15) and ?? 95.506(17)??. The atomic arrangement has been solved and refined to an R value of 0.019. The arrangement of atoms consists of alternating (011) slabs of orthosilicate groups and carbonate groups, with no sharing of oxygen atoms between anionic complexes in adjacent slabs. Y1 atoms separate adjacent tetrahedra along [100] within the orthosilicate slab, and Y2 atoms separate adjacent carbonate groups along [100] within the carbonate slab. Adjacent orthosilicate and carbonate slabs are linked in (100) by bonding Y atoms from each slab to oxygen atoms of adjacent slabs, in the form of YO8 polyhedra. The Y1 atoms exist in Y12O14 dimers in the orthosilicate slab, and the Y2 atoms exist in continuous [011] ribbons of edge-sharing Y2O8 polyhedra in the carbonate slab.

Thermal expansion and elastic anisotropy in single crystal Al2O3 and SiC reinforcements

NASA Technical Reports Server (NTRS)

Salem, Jonathan A.; Li, Zhuang; Bradt, Richard C.

1994-01-01

In single crystal form, SiC and Al2O3 are attractive reinforcing components for high temperature composites. In this study, the axial coefficients of thermal expansion and single crystal elastic constants of SiC and Al2O3 were used to determine their coefficients of thermal expansion and Young's moduli as a function of crystallographic orientation and temperature. SiC and Al2O3 exhibit a strong variation of Young's modulus with orientation; however, their moduli and anisotropies are weak functions of temperature below 1000 C. The coefficients of thermal expansion exhibit significant temperature dependence, and that of the non-cubic Al2O3 is also a function of crystallographic orientation.

Crystal growth and characterization of Ce:Gd3(Ga,Al)5O12 single crystal using floating zone method in different O2 partial pressure

NASA Astrophysics Data System (ADS)

Yoshikawa, Akira; Fujimoto, Yutaka; Yamaji, Akihiro; Kurosawa, Shunsuke; Pejchal, Jan; Sugiyama, Makoto; Wakahara, Shingo; Futami, Yoshisuke; Yokota, Yuui; Kamada, Kei; Yubuta, Kunio; Shishido, Toetsu; Nikl, Martin

2013-09-01

Multicomponent garnet Ce:Gd3(Ga,Al)5O12 (Ce:GAGG) single crystals show very high light yield with reasonably fast scintillation response. Therefore, they can be promising scintillators for gamma-ray detection. However, in the decay curve a very slow component does exist. Therefore, it is necessary to optimize further the crystal growth technology of Ce:GAGG. In this study, Ce:GAGG single crystals were grown by the floating zone (FZ) method under atmospheres of various compositions such as Ar 100%, Ar 80% + O2 20%, Ar 60% + O2 40% and O2 100%. Radioluminescence spectra are dominated by the band at about 540 nm due to Ce3+ 5d1-4f transition. The Ce:GAGG single crystal grown under Ar atmosphere shows an intense slower decay component. It can be related to the processes of the delayed radiative recombination and thermally induced ionization of 5d1 level of Ce3+ center possibly further affected by oxygen vacancies. This slower decay process is significantly suppressed in the samples grown under the O2 containing atmosphere.

Optimization of single crystals of solid electrolytes with tysonite-type structure (LaF3) for conductivity at 293 K: 2. Nonstoichiometric phases R 1- y M y F3- y ( R = La-Lu, Y; M = Sr, Ba)

NASA Astrophysics Data System (ADS)

Sorokin, N. I.; Sobolev, B. P.; Krivandina, E. A.; Zhmurova, Z. I.

2015-01-01

Single crystals of fluorine-conducting solid electrolytes R 1 - y Sr y F3 - y and R 1 - y Ba y F3 - y ( R = La-Lu, Y) with a tysonite-type structure (LaF3) have been optimized for room-temperature conductivity σ293 K. The optimization is based on high-temperature measurements of σ( T) in two-component nonstoichiometric phases R 1 - y M y F3 - y ( M = Sr, Ba) as a function of the MF2 content. Optimization for thermal stability is based on studying the phase diagrams of MF2- RF3 systems ( M = Sr, Ba) and the behavior of nonstoichiometric crystals upon heating when measuring temperature dependences σ( T). Single crystals of many studied R 1 - y Sr y F3 - y and R 1 - y Ba y F3 - y phases have σ293 K values large enough to use these materials in solid-state electrochemical devices (chemical sensors, fluorine-ion batteries, accumulators, etc.) operating at room temperature.

The Single-Crystal Elasticity of Yttria (Y2O3) to High Temperature

NASA Technical Reports Server (NTRS)

Kriven, Waltraud M.; Palko, James W.; Sinogeikin, Stanislav V.; Bass, Jay D.; Sayir, Ali; Levine, Stanley R. (Technical Monitor)

2000-01-01

The single-crystal elastic moduli of yttria have been measured by Brillouin spectroscopy up to 1200 C. The room temperature values obtained are C11 = 223.6 +/- 0.6 GPa, C44 = 74.6 +/- 0.5 GPa, and C12 = 112.4 +/- 1.0 GPa. The resulting bulk and (Voigt-Reuss-Hill) shear moduli are K = 149.5 +/- 1.0 GPa and G(sub VRH) = 66.3 +/- 0.8 GPa, respectively. These agree much more closely with experimental values reported for polycrystalline samples than do previous single-crystal measurements. Linear least squares regressions to the variation of bulk and shear moduli with temperature result in derivatives of dK/dT = -17 +/- 2 MPa/degC and dG(sub VRH)/dT = -8 +/- 2 MPa/degC. Elastic anisotropy was found to remain essentially constant over the temperature range studied.

Ultra-fast scintillation properties of β-Ga2O3 single crystals grown by Floating Zone method

NASA Astrophysics Data System (ADS)

He, Nuotian; Tang, Huili; Liu, Bo; Zhu, Zhichao; Li, Qiu; Guo, Chao; Gu, Mu; Xu, Jun; Liu, Jinliang; Xu, Mengxuan; Chen, Liang; Ouyang, Xiaoping

2018-04-01

In this investigation, β-Ga2O3 single crystals were grown by the Floating Zone method. At room temperature, the X-ray excited emission spectrum includes ultraviolet and blue emission bands. The scintillation light output is comparable to the commercial BGO scintillator. The scintillation decay times are composed of the dominant ultra-fast component of 0.368 ns and a small amount of slightly slow components of 8.2 and 182 ns. Such fast component is superior to most commercial inorganic scintillators. In contrast to most semiconductor crystals prepared by solution method such as ZnO, β-Ga2O3 single crystals can be grown by traditional melt-growth method. Thus we can easily obtain large bulk crystals and mass production.

Tunable bandgap in hybrid perovskite CH{sub 3}NH{sub 3}Pb(Br{sub 3−y}X{sub y}) single crystals and photodetector applications

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

Wang, L.; Duan, R. F.; Huang, F.

We report the synthesis of CH{sub 3}NH{sub 3}Pb(Br{sub 3−y}X{sub y}) (X=Cl and I) single crystals via a stepwise temperature control approach. High-quality CH{sub 3}NH{sub 3}Pb(Br{sub 3−y}X{sub y}) crystals with a tunable bandgap from 1.92 eV to 2.53 eV have been prepared successfully in this way. And further experiments revealed the influence of halogen content and preparation temperature on the structural and optical properties of these crystals. It is observed that chlorine can lower the critical nucleation energy, which results in crystallizing at lower temperature with the chlorine content increasing, while the nucleation energy increases slowly with increasing iodine content. Moreover,more » in contrast to Frank–van der Merwe growth with low heating rate, high heating rate leads to a mass of small size single crystals and Stranski-Krastanov growth. The single crystals with tunable band gap and impressive characteristics enable us to fabricate high performance photodetectors for different wavelengths.« less

Growth and physicochemical properties of organometallic (DL)-trithioureatartrato-O1,O2,O3-cadmium(II) single crystals

NASA Astrophysics Data System (ADS)

Sathyamoorthy, K.; Vinothkumar, P.; Irshad Ahamed, J.; Murali Manohar, P.; Priya, M.; Liu, Jinghe

2018-04-01

Single crystals of organometallic (DL)-trithioureatartrato-O1,O2,O3-cadmium(II) (TUDLC) have been grown from methanol solution by using the slow evaporation of solvent growth technique. The lattice structure and crystalline perfection have been determined by carrying out single crystal X-ray diffraction and high resolution X-ray diffraction measurements. The grown crystal was characterized thermally and mechanically by carrying out thermo-gravimetric and micro hardness measurements. The linear and nonlinear optical characterizations were made by carrying out optical transmittance, surface laser damage threshold, particle size-dependent second harmonic generation (SHG) efficiency and photo conductivity measurements. The grown crystal was electrically characterized by carrying out frequency-dependent dielectric measurements. Chemical etching study was also carried out and the dislocation density was estimated. Results obtained in the present study indicate that the grown TUDLC crystal is optically transparent with lower cut-off wavelength 304 nm, mechanically soft, thermally stable up to 101 °C and NLO active with SHG efficiency 2.13 (in KDP unit). The grown crystal is found to have considerably large size, good crystalline perfection, large specific heat capacity, higher surface laser damage threshold and negative photoconductivity.

Complete matrix properties of [001](c) and [011](c) poled 0.33Pb(In(1/2)Nb(1/2))O(3)-0.38Pb(Mg(1/3)Nb(2/3))O(3)-0.29PbTiO(3) single crystals.

PubMed

Sun, Enwei; Zhang, Rui; Wu, Fengmin; Cao, Wenwu

2013-03-15

The elastic, piezoelectric, and dielectric properties of [001](c) and [011](c) poled 0.33Pb(In(1/2)Nb(1/2))O(3)-0.38Pb(Mg(1/3)Nb(2/3))O(3)-0.29PbTiO(3) single crystals have been fully characterized at room temperature, and the temperature and frequency dependence of the dielectric susceptibility ε(33) were also measured. The depoling temperature of this crystal is more than 20 °C higher than that of the corresponding binary 0.71Pb(Mg(1/3)Nb(2/3))O(3)-0.29PbTiO(3) system. From the measured P-E hysteresis loops, the coercive fields along [001](c) and [011](c) directions have been determined to be 6.0 kV/cm and 6.6 kV/cm, respectively, which indicate that these domain engineered ternary relaxor-based ferroelectric single crystals are excellent candidates for high-power applications.

Synthesis of a mesoporous single crystal Ga2O3 nanoplate with improved photoluminescence and high sensitivity in detecting CO.

PubMed

Yan, Shicheng; Wan, Lijuan; Li, Zhaosheng; Zhou, Yong; Zou, Zhigang

2010-09-14

A new approach is proposed to synthesize a mesoporous single crystal Ga(2)O(3) nanoplate by heating a single crystal nanoplate of GaOOH, which involves an ion exchange between KGaO(2) and CH(3)COOH at room temperature for the formation of GaOOH and pseudomorphic and topotactic phase transformation from GaOOH to Ga(2)O(3).

Thermal conductivity of Ca3Co2O6 single crystals

NASA Astrophysics Data System (ADS)

Che, H. L.; Shi, J.; Wu, J. C.; Rao, X.; Liu, X. G.; Zhao, X.; Sun, X. F.

2018-05-01

Ca3Co2O6 is a rare example of one-dimensional Ising spin-chain material with the moments preferentially aligned along the c axis. In this work, we study the c-axis thermal conductivity (κc) of Ca3Co2O6 single crystal at low temperatures down to 0.3 K and in magnetic fields up to 14 T. The zero-field κc(T) shows a large phonon peak and can be well fitted by using the classical Debye model, which indicates that the heat transport is purely phononic. Moreover, the low-T κc(H) isotherms with H || c display a field-independent behavior. These results indicate that there is no contribution of magnetic excitations to the thermal conductivity in Ca3Co2O6, neither carrying heat nor scattering phonons, which can be attributed to the Ising-like spin anisotropy.

Realization of single terminated surface of perovskite oxide single crystals and their band profile: (LaAlO3)0.3(Sr2AlTaO6)0.7, SrTiO3 and KTaO3 case study

NASA Astrophysics Data System (ADS)

Tomar, Ruchi; Wadehra, Neha; Budhiraja, Vaishali; Prakash, Bhanu; Chakraverty, S.

2018-01-01

To characterize the physical properties of thin films without ambiguity and design interface with new functionalities, it is essential to have detailed knowledge of physical properties and appropriate estimation of the band profile of perovskite oxide substrates. We have developed and demonstrated a chemical free unified framework to realize single terminated surface of KTaO3, (LaAlO3)0.3 (Sr2AlTaO6)0.7 and SrTiO3 (001) oriented single crystals. The electronic band line-up of these single crystal substrates, using a combination of optical spectroscopy and Kelvin Probe Force Microscopy, has been constructed. A polar-polar interface of KTaO3 and LaBO3 (B-Transition metal ion) before and after the possible surface/electronic reconstruction has also been schematically presented.

Electrical conduction mechanism in La3Ta0.5Ga5.3Al0.2O14 single crystals

PubMed Central

Yaokawa, Ritsuko; Aota, Katsumi; Uda, Satoshi

2013-01-01

The electrical conduction mechanism in La3Ta0.5Ga5.3Al0.2O14 (LTGA) single crystals was studied by nonstoichiometric defect formation during crystal growth. Since stoichiometric LTGA is not congruent, the single crystal grown from the stoichiometric melt was Ta-poor and Al-rich, where Al atoms were substituted not only in Ga sites but also in Ta sites. The population of the substitutional Al in Ta sites increased with increasing oxygen partial pressure during growth (growth-pO2) in the range from 0.01 to 1 atm. Below 600 °C, substitutional Al atoms in Ta sites were ionized to yield holes, and thus the electrical conductivity of the LTGA crystal depended on temperature and the growth-pO2. The dependence of the electrical conductivity on the growth-pO2 decreased as temperature increased. The temperature rise increases ionic conductivity, for which the dominant carriers are oxygen defects formed by the anion Frenkel reaction. PMID:24396153

Peak effect in untwinned YBa 2Cu 3O 7-δ single crystals

NASA Astrophysics Data System (ADS)

D'Anna, G.; André, M.-O.; Indenbom, M. V.; Benoit, W.

1994-12-01

We report on the observation of a weak effect of the critical current density in untwinned YBa 2Cu 3O 7-δ single crystals of different purity, using a low frequency torsion pendulum. We construct the peak effect line and the irreversibility line.

Absorption of Dy3+ and Nd3+ ions in Ba R 2F8 single crystals

NASA Astrophysics Data System (ADS)

Apollonov, V. V.; Pushkar', A. A.; Uvarova, T. V.; Chernov, S. P.

2008-09-01

The Dy3+ absorption and excitation spectra of BaY2F8 and BaYb2F8 single crystals are investigated in the ultraviolet, vacuum ultraviolet, and visible ranges at a temperature of 300 K. These crystals exhibit intense broad absorption bands due to the spin-allowed 4 f-5 d transitions in the range (56-78) × 10-3 cm-1 and less intense absorption bands that correspond to the spin-forbidden transitions in the range (50-56) × 10-3 cm-1. The Nd3+ absorption spectra of BaY2F8 single crystals are studied in the range (34-82) × 10-3 cm-1 at 300 K for different crystal orientations.

Synthesis of Mesoporous Single Crystal Co(OH)2 Nanoplate and Its Topotactic Conversion to Dual-Pore Mesoporous Single Crystal Co3O4.

PubMed

Jia, Bao-Rui; Qin, Ming-Li; Li, Shu-Mei; Zhang, Zi-Li; Lu, Hui-Feng; Chen, Peng-Qi; Wu, Hao-Yang; Lu, Xin; Zhang, Lin; Qu, Xuan-Hui

2016-06-22

A new class of mesoporous single crystalline (MSC) material, Co(OH)2 nanoplates, is synthesized by a soft template method, and it is topotactically converted to dual-pore MSC Co3O4. Most mesoporous materials derived from the soft template method are reported to be amorphous or polycrystallined; however, in our synthesis, Co(OH)2 seeds grow to form single crystals, with amphiphilic block copolymer F127 colloids as the pore producer. The single-crystalline nature of material can be kept during the conversion from Co(OH)2 to Co3O4, and special dual-pore MSC Co3O4 nanoplates can be obtained. As the anode of lithium-ion batteries, such dual-pore MSC Co3O4 nanoplates possess exceedingly high capacity as well as long cyclic performance (730 mAh g(-1) at 1 A g(-1) after the 350th cycle). The superior performance is because of the unique hierarchical mesoporous structure, which could significantly improve Li(+) diffusion kinetics, and the exposed highly active (111) crystal planes are in favor of the conversion reaction in the charge/discharge cycles.

Optical and scintillation characteristics of Gd2YAl2Ga3O12:Ce and Lu2YAl2Ga3O12:Ce single crystals

NASA Astrophysics Data System (ADS)

Chewpraditkul, Warut; Sakthong, Ongsa; Pattanaboonmee, Nakarin; Chewpraditkul, Weerapong; Szczesniak, Tomasz; Swiderski, Lukasz; Moszynski, Marek; Kamada, Kei; Yoshikawa, Akira; Nikl, Martin

2017-06-01

The optical and scintillation characteristics of Gd2YAl2Ga3O12:Ce and Lu2YAl2Ga3O12:Ce single crystals are investigated. At 662 keV γ-rays, light yield (LY) of 37,900 ph/MeV and energy resolution of 7.0% obtained for Gd2YAl2Ga3O12:Ce are superior to those of 18,900 ph/MeV and 11.5% obtained for Lu2YAl2Ga3O12:Ce. Scintillation decays are measured using the time-correlated single photon counting technique. A fast component decay time of 45 ns with relative intensity of 88% obtained for Lu2YAl2Ga3O12:Ce is superior to that of 50 ns (65%) for Gd2YAl2Ga3O12:Ce. The linear attenuation coefficient at 662 keV γ-rays is also determined and discussed.

Field induced 4f5d [Re(salen)]2O3[Dy(hfac)3(H2O)]2 single molecule magnet.

PubMed

Pointillart, Fabrice; Bernot, K; Sessoli, R; Gatteschi, D

2010-05-03

The reaction between the mononuclear [ReO(salen)(OMe)] (salen(2-) = N,N'-ethan-1,2-diylbis(salicylidenamine) dianion) and Dy(hfac)(3).2H(2)O (hfac(-) = 1,1,1,5,5,5-hexafluoroacetylacetonate anion) complexes lead to the formation of a compound with the formula {[Re(salen)](2)O(3)[Dy(hfac)(3)(H(2)O)](2)}(CHCl(3))(2)(CH(2)Cl(2))(2) noted (Dy(2)Re(2)). This compound has been characterized by single crystal and powder X-ray diffraction and has been found isostructural to the Y(III) derivative (Y(2)Re(2)) that we previously reported. The cyclic voltammetry demonstrates the redox activity of the system. The characterization of both static and dynamic magnetic properties is reported. Static magnetic data has been analyzed after the cancellation of the crystal field contribution by two different methods. Weak ferromagnetic exchange interactions between the Dy(III) ions are highlighted. The compound Dy(2)Re(2) displays slow relaxation of the magnetization when an external magnetic field is applied. Alternating current susceptibility shows a thermally activated behavior with pre-exponential factors of 7.13 (+/-0.10) x 10(-6) and 5.76 (+/-0.27) x 10(-7) s, and energy barriers of 4.19 (+/-0.02) and 8.52 (+/-0.55) K respectively for low and high temperature regimes.

Magnetic and magnetostrictive behavior of Dy 3+ doped CoFe 2O 4 single crystals grown by flux method

NASA Astrophysics Data System (ADS)

Kambale, Rahul C.; Song, K. M.; Won, C. J.; Lee, K. D.; Hur, N.

2012-02-01

We studied the effect of Dy 3+ content on the magnetic properties of cobalt ferrite single crystal. The single crystals of CoFe 1.9Dy 0.1O 4 were grown by the flux method using Na 2B 4O 7.10 H 2O (Borax) as a solvent (flux). The black and shiny single crystals were obtained as a product. The X-ray diffraction analysis at room temperature confirmed the spinel cubic structure with lattice constant a=8.42 Å of the single crystals. The compositional analysis endorses the presence of constituents Co, Fe and Dy elements after sintering at 1300 °C within the final structure. The magnetic hysteresis measurements at various temperatures viz. 10 K, 100 K, 200 K and 300 K reveal the soft ferrimagnetic nature of the single crystal than that of for pure CoFe 2O 4. The observed saturation magnetization ( Ms) and coercivity ( Hc) are found to be lower than that of pure CoFe 2O 4 single crystal. The magnetostriction ( λ) measurement was carried out along the [001] direction. The magnetic measurements lead to conclude that the present single crystals can be used for magneto-optic recording media.

Superconductor-to-insulator transition and transport properties of underdoped YBa2Cu3O(y) crystals.

PubMed

Semba, K; Matsuda, A

2001-01-15

The carrier-concentration-driven superconductor-to-insulator (SI) transition as well as transport properties in underdoped YBa2Cu3O(y) twinned crystals is studied. The SI transition takes place at y approximately 6.3, carrier concentration n(SI)H approximately 3x10(20) cm(-3), anisotropy rho(c)/rho(ab) approximately 10(3), and the threshold resistivity rho(SI)ab approximately 0.8 mOmega cm which corresponds to a critical sheet resistance h/4e2 approximately 6.5 kOmega per CuO2 bilayer. The evolution of a carrier, nH infiniti y - 6.2, is clearly observed in the underdoped region. The resistivity and Hall coefficient abruptly acquire strong temperature dependence at y approximately 6.5 indicating a radical change in the electronic state.

Hydrogen centers and the conductivity of In 2O 3 single crystals

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

Yin, Weikai; Smithe, Kirby; Weiser, Philip

2015-02-24

A series of infrared absorption experiments and complementary theory have been performed in order to determine the properties of OH and OD centers in In 2O 3 single crystals. Annealing In 2O 3 samples in H 2 or D 2 at temperatures near 450°C produces an n-type layer ≈0.06mm thick with an n-type doping of 1.6×1019 cm -3. The resulting free-carrier absorption is correlated with an OH center with a vibrational frequency of 3306 cm -1 that we associate with interstitial H +. Additional O-H (O-D) vibrational lines are assigned to metastable configurations of the interstitial H +(D +) centermore » and complexes of H (D) with In vacancies. In addition, unlike other oxides studied recently where H trapped at an oxygen vacancy is the dominant shallow donor (ZnO and SnO 2, for example), interstitial H + is found to be the dominant H-related shallow donor in In 2O 3.« less

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

DOEpatents

Todt, V.; Miller, D.J.; Shi, D.; Sengupta, S.

1998-07-07

A method of fabricating bulk YBa{sub 2}Cu{sub 3}O{sub x} where compressed powder oxides and/or carbonates of Y and Ba and Cu present in mole ratios to form YBa{sub 2}Cu{sub 3}O{sub x} are heated in the presence of a Nd{sub 1+x}Ba{sub 2{minus}x}Cu{sub 3}O{sub y} seed crystal to a temperature sufficient to form a liquid phase in the YBa{sub 2}Cu{sub 3}O{sub x} while maintaining the seed crystal solid. The materials are slowly cooled to provide a YBa{sub 2}Cu{sub 3}O{sub x} material having a predetermined number of domains between 1 and 5. Crack-free single domain materials can be formed using either plate shaped seed crystals or cube shaped seed crystals with a pedestal of preferential orientation material. 7 figs.

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

DOEpatents

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

1998-01-01

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

Luminescence and Excitation Spectra of U 3+ doped RbY 2 Cl 7 Single Crystals

DOE PAGES

Karbowiak, M.; Murdoch, K.; Drożdżyński, J.; ...

1996-08-01

Uranium(3+) doped single crystals of RbY 2 Cl 7 with a uranium concentration of 0.05% and 0.2% were grown by the Bridgman-Stockbarger method using RbU 2 Cl 7 as the doping substance. Polished plates of ca. 5 mm in diameter were used for measurements of luminescence and excitation spectra. And since the U 3+ ions occupy two somewhat different site symmetries, a splitting of all observed f-f bands was observed. Furthermore, the analysis of the spectra enabled definitively an assignment of 22 crystal field bands for both site symmetries as well as the total crystal field splitting of the groundmore » level, equal to 473 cm -1 and 567 cm -1 for the first and second site symmetry, respectively.« less

Rise and fall of ferromagnetism in O-irradiated Al{sub 2}O{sub 3} single crystals

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

Li, Qiang; China Spallation Neutron Source, Institute of High Energy Physics, Chinese Academy of Sciences, Dongguan 523803; Xu, Juping

2015-06-21

In dilute magnetic semiconductors studies, sapphire was usually used as non-magnetic substrate for films. We observed weak ferromagnetic component in Al{sub 2}O{sub 3} single crystal substrate, and excluded the possibility of ferromagnetic contaminations carefully by inductively coupled plasma mass spectrometry and X-ray photoelectron spectroscopy. The ferromagnetism rise and fall during the process of annealing-oxygen irradiation-annealing of the sapphire. The ferromagnetic changes are consistent with Al-vacancy related defects detected by positron annihilation spectroscopy. With first-principle calculations, we confirm that Al-vacancy can introduce magnetic moment for 3 μB in Al{sub 2}O{sub 3} crystal and form stable V{sub Al}-V{sub Al} ferromagnetic coupling at roommore » temperature.« less

Photomagnetic switching of heterometallic complexes [M(dmf)4(H2O)3(mu-CN)Fe(CN)5].H2O (M=Nd, La, Gd, Y) analyzed by single-crystal X-ray diffraction and ab initio theory.

PubMed

Svendsen, Helle; Overgaard, Jacob; Chevallier, Marie A; Collet, Eric; Chen, Yu-Sheng; Jensen, Frank; Iversen, Bo B

2010-06-25

Single-crystal X-ray diffraction measurements have been carried out on [Nd(dmf)(4)(H(2)O)(3)(mu-CN)Fe(CN)(5)].H(2)O (1; dmf=dimethylformamide), [Nd(dmf)(4)(H(2)O)(3)(mu-CN)Co(CN)(5)].H(2)O (2), [La(dmf)(4)(H(2)O)(3)(mu-CN)Fe(CN)(5)].H(2)O (3), [Gd(dmf)(4)(H(2)O)(3)(mu-CN)Fe(CN)(5)].H(2)O (4), and [Y(dmf)(4)(H(2)O)(3)(mu-CN)Fe(CN)(5)].H(2)O (5), at 15(2) K with and without UV illumination of the crystals. Significant changes in unit-cell parameters were observed for all the iron-containing complexes, whereas 2 showed no response to UV illumination. Photoexcited crystal structures have been determined for 1, 3, and 4 based on refinements of two-conformer models, and excited-state occupancies of 78.6(1), 84(6), and 86.6(7)% were reached, respectively. Significant bond-length changes were observed for the Fe-ligand bonds (up to 0.19 A), the cyano bonds (up to 0.09 A), and the lanthanide-ligand bonds (up to 0.10 A). Ab initio theoretical calculations were carried out for the experimental ground-state geometry of 1 to understand the electronic structure changes upon UV illumination. The calculations suggest that UV illumination gives a charge transfer from the cyano groups on the iron atom to the lanthanide ion moiety, {Nd(dmf)(4)(H(2)O)(3)}, with a distance of approximately 6 A from the iron atom. The charge transfer is accompanied by a reorganization of the spin state on the {Fe(CN)(6)} complex, and a change in geometry that produces a metastable charge-transfer state with an increased number of unpaired electrons, thus accounting for the observed photomagnetic effect.

Evolution of electrical properties and domain configuration of Mn modified Pb(In1/2Nb1/2)O3-PbTiO3 single crystals

NASA Astrophysics Data System (ADS)

Qiao, Huimin; He, Chao; Yuan, Feifei; Wang, Zujian; Li, Xiuzhi; Liu, Ying; Guo, Haiyan; Long, Xifa

2018-04-01

The acceptor doped relaxor-based ferroelectric materials are useful for high power applications such as probes in ultrasound-guided high intensity focused ultrasound therapy. In addition, a high Curie temperature is desired because of wider temperature usage and improved temperature stability. Previous investigations have focused on Pb(Mg1/3Nb2/3)O3-PbTiO3 and Pb(Zn1/3Nb2/3)O3-PbTiO3 systems, which have a ultrahigh piezoelectric coefficient and dielectric constant, but a relatively low Curie temperature. It is desirable to study the binary relaxor-based system with a high Curie temperature. Therefore, Pb(In1/2Nb1/2)O3-PbTiO3 (PINT) single crystals were chosen to study the Mn-doped influence on their electrical properties and domain configuration. The evolution of ferroelectric hysteresis loops for doped and virgin samples exhibit the pinning effect in Mn-doped PINT crystals. The relaxation behaviors of doped and virgin samples are studied by fit of the modified Curie-Weiss law and Volgel-Fucher relation. In addition, a short-range correlation length was fitted to study the behavior of polar nanoregions based on the domain configuration obtained by piezoresponse force microscopy. Complex domain structures and smaller short-range correlation lengths (100-150 nm for Mn-doped PINT and >400 nm for pure PINT) were obtained in the Mn-doped PINT single crystals.

Low-temperature specific heat of single-crystal Bi2CaSr2Cu2O8 and Tl2Ca2Ba2Cu3O10

NASA Astrophysics Data System (ADS)

Urbach, J. S.; Mitzi, D. B.; Kapitulnik, A.; Wei, J. Y. T.; Morris, D. E.

1989-06-01

We report specific-heat measurements from 2 to 15 K on single crystals of Bi2CaSr2Cu2O8 and Tl2Ca2Ba2Cu3O10 We find low-temperature deviations from the Debye law that can be attributed to spin-glass behavior of a small concentration of isolated impurity copper moments. At higher temperatures, we observe contributions to the specific heat that can be attributed to a soft-phonon mode, possibly associated with the superstructure in the Bi-O and Tl-O layers. From our single-crystal data, we conclude that the thallium- and bismuth-based copper oxide superconductors show no measurable linear term in the specific heat [γ(0)<=1 mJ/mole K2].

Dependences of the density of M 1- x R x F2 + x and R 1- y M y F3- y single crystals ( M = Ca, Sr, Ba, Cd, Pb; R means rare earth elements) on composition

NASA Astrophysics Data System (ADS)

Sorokin, N. I.; Krivandina, E. A.; Zhmurova, Z. I.

2013-11-01

The density of single crystals of nonstoichiometric phases Ba1 - x La x F2 + x (0 ≤ x ≤ 0.5) and Sr0.8La0.2 - x Lu x F2.2 (0 ≤ x ≤ 0.2) with the fluorite (CaF2) structure type and R 1 - y Sr y F3 - y ( R = Pr, Nd; 0 ≤ y ≤ 0.15) with the tysonite (LaF3) structure type has been measured. Single crystals were grown from a melt by the Bridgman method. The measured concentration dependences of single crystal density are linear. The interstitial and vacancy models of defect formation in the fluorite and tysonite phases, respectively, are confirmed. To implement the composition control of single crystals of superionic conductors M 1 - x R x F2 + x and R 1 - y M y F3 - y in practice, calibration graphs of X-ray density in the MF2- RF3 systems ( M = Ca, Sr, Ba, Cd, Pb; R = La-Lu, Y) are plotted.

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.

Melt growth and properties of bulk BaSnO3 single crystals

NASA Astrophysics Data System (ADS)

Galazka, Z.; Uecker, R.; Irmscher, K.; Klimm, D.; Bertram, R.; Kwasniewski, A.; Naumann, M.; Schewski, R.; Pietsch, M.; Juda, U.; Fiedler, A.; Albrecht, M.; Ganschow, S.; Markurt, T.; Guguschev, C.; Bickermann, M.

2017-02-01

We present the first-time growth of bulk BaSnO3 single crystals from the melt by direct solidification, their basic electrical and optical properties as well as their structural quality. Our measurement of the melting point (MP) of BaSnO3 amounts to 1855 °C  ±  25 K. At this temperature an intensive decomposition and non-stoichiometric evaporation takes place as the partial pressure of SnO(g) is about 90 times higher than that of BaO(g). X ray powder diffraction identified only the BaSnO3 perovskite phase, while narrow rocking curves having a full width at half maximum of 26 arcsec and etch pit densities below 106 cm-2 confirm a high degree of structural perfection of the single crystals. In this respect they surpass the structural properties of those single crystals that were reported in the literature. The electrical conductivity of nominally undoped crystals depends on the growth conditions and ranges from insulating to medium n-type conductivity. After post-growth annealing in an oxidizing atmosphere undoped crystals are generally insulating. Doping the crystals with lanthanum during growth results in a high n-type conductivity. For a La doping concentration of 0.123 wt.% we measured an electron concentration of 3.3  ×  1019 cm-3 and an electron mobility of 219 cm2 V-1 s-1. Based on optical absorption measurements we determined an energy of 3.17  ±  0.04 eV at 5 K and of 2.99  ±  0.04 eV at 297 K for the indirect band gap of BaSnO3.

Polarized electronic absorption spectra of Cr2SiO4 single crystals

NASA Astrophysics Data System (ADS)

Furche, A.; Langer, K.

Polarized electronic absorption spectra, E∥a(∥X), E∥b(∥Y) and E∥c(∥Z), in the energy range 3000-5000 cm-1 were obtained for the orthorhombic thenardite-type phase Cr2SiO4, unique in its Cr2+-allocation suggesting some metal-metal bonding in Cr2+Cr2+ pairs with Cr-Cr distance 2.75 Å along [001]. The spectra were scanned at 273 and 120 K on single crystal platelets ∥(100), containing optical Y and Z, and ∥(010), containing optical X and Z, with thicknesses 12.3 and 15.6 μm, respectively. Microscope-spectrometric techniques with a spatial resolution of 20 μm and 1 nm spectral resolution were used. The orientations were obtained by means of X-ray precession photographs. The xenomorphic, strongly pleochroic crystal fragments (X deeply greenish-blue, Y faint blue almost colourless, Z deeply purple almost opaque) were extracted from polycrystalline Cr2SiO4, synthesized at 35 kbar, above 1440 °C from high purity Cr2O3, Cr (10% excess) and SiO2 in chromium capsules. The Cr2SiO4-phase was identified by X-ray diffraction (XRD). Four strongly polarized bands, at about 13500 (I), 15700 (II), 18700 (III) and 19700 (IV) cm-1, in the absorption spectra of Cr2SiO4 single crystals show properties (temperature behaviour of linear and integral absorption coefficients, polarization behaviour, molar absorptivities) which are compatible with an assignment to localized spin-allowed transitions of Cr2+ in a distorted square planar coordination of point symmetry C2. The crystal field parameter of Cr2+ is estimated to be 10 Dq =10700 cm-1. A relatively intense, sharp band at 18400 cm-1 and three other minor features can, from their small half widths, be assigned to spin-forbidden dd-transitions of Cr2+. The intensity of such bands strongly decreases on decreasing temperature. The large half widths, near 5000 cm-1 of band III are indicative of some Cr-Cr interactions, i.e. δ-δ* transitions of Cr24+, whereas the latter alone would be in conflict with the strong

Growth and electrical properties of (Mn,F) co-doped 0.92Pb(Zn 1/3Nb 2/3)O 3-0.08PbTiO 3 single crystal

NASA Astrophysics Data System (ADS)

Zhang, Shujun; Lebrun, Laurent; Randall, Clive A.; Shrout, Thomas R.

2004-06-01

The growth and characterization of (Mn,F) doped Pb(Zn 1/3Nb 2/3)O 3-PbTiO 3 (PZNT) single crystals are reported in this paper. The typical single crystal obtained is up to 30 mm size with dark brown color. The crystal lattice parameters of doped PZNT crystal are slightly decreased compared to the pure one. The room temperature dielectric permittivity along <0 0 1> direction is about 6000, which is lower than that of the pure PZNT8 because of the dopants. The Curie temperature of the doped crystal is about 180°C while the ferroelectric phase transition temperature is around 100°C, which are higher than those of the pure PZNT8 single crystal. The remnant polarization and coercive field of <0 0 1> oriented doped crystal measured at 1 Hz and 10 kV/cm field are about 27 μC/cm 2 and 4.2 kV/cm, respectively. The room temperature mechanical quality factor is ˜300. Piezoelectric coefficient of <0 0 1> oriented doped crystal is higher than 3500 pC/N and the longitudinal electromechanical coupling factor is larger than 93%. The piezoelectric properties of doped PZNT single crystal with temperature and orientations are also reported in this paper. The valence state of the manganese dopant was determined by electron spin resonance, indicating no Mn 4+ in the crystals, suggesting the valence of manganese ions in PZNT crystals may be 2+, which acts as a hardener, stabilizes the domain wall and pins the domain wall motion, on the other hand, the dopant will enter Ti 4+ position, shifting the crystal composition to higher PT content.

Extreme anisotropy and anomalous transport properties of heavily electron doped Lix(NH3)yFe2Se2 single crystals

NASA Astrophysics Data System (ADS)

Sun, Shanshan; Wang, Shaohua; Yu, Rong; Lei, Hechang

2017-08-01

We report the growth of heavily electron doped Li-NH3 intercalated FeSe single crystals that are free of material complexities and allow access to the intrinsic superconducting properties. Lix(NH3)yFe2Se2 single crystals show extremely large electronic anisotropy in both normal and superconducting states. They also exhibit anomalous transport properties in the normal state, which are believed to possibly be related to the anisotropy of relaxation time and/or temperature-dependent electron carrier concentration. Taking into account the great chemical flexibility of intercalants in the system, our findings provide a platform to understanding the origin of superconductivity in FeSe-related superconductors.

Inheritance of Crystallographic Orientation during Lithiation/Delithiation Processes of Single-Crystal α-Fe2O3 Nanocubes in Lithium-Ion Batteries.

PubMed

Ma, Xiaowei; Zhang, Manyu; Liang, Chongyun; Li, Yuesheng; Wu, Jingjing; Che, Renchao

2015-11-04

Iron oxides are very promising anode materials based on conversion reactions for lithium-ion batteries (LIBs). During conversion processes, the crystal structure and composition of the electrode material are drastically changed. Surprisingly, in our study, inheritance of a crystallographic orientation was found during lithiation/delithiation processes of single-crystal α-Fe2O3 nanocubes by ex situ transmission electron microscopy. Single-crystal α-Fe2O3 was first transformed into numerous Fe nanograins embedded in a Li2O matrix, and then the conversion between Fe and FeO nanograins became the main reversible electrochemical reaction for energy storage. Interestingly, these Fe/FeO nanograins had almost the same crystallographic orientation, indicating that the lithiated/delithiated products can inherit the crystallographic orientation of single-crystal α-Fe2O3. This finding is important for understanding the detailed electrochemical conversion processes of iron oxides, and this feature may also exist during lithiation/delithiation processes of other transition-metal oxides.

Temperature and electric-field induced phase transition behavior and electrical properties of [001]-oriented 0.23Pb(In1/2Nb1/2)O3-0.47Pb(Mg1/3Nb2/3)O3-0.3PbTiO3-Mn single crystals

NASA Astrophysics Data System (ADS)

Zhang, Zhang; Chen, Jianwei; Xu, Jialin; Li, Xiaobing; Luo, Haosu

2017-12-01

The temperature and electric-field induced phase transition behavior and dielectric, piezoelectric, and ferroelectric properties of [001]-oriented 0.23Pb(In1/2Nb1/2)O3-0.47Pb(Mg1/3Nb2/3)O3-0.3PbTiO3-Mn (PIMNT-Mn) single crystals were investigated. Dielectric performance analysis and temperature-dependent Raman spectra show three apparent ferroelectric phase transition temperatures around 120 °C(TR-M),145 °C(TM-T), and 170 °C(TT-C), respectively. In addition, the temperature dependence of the relative Raman intensities of Lorentzian peaks indicates the poled PIMNT-Mn single crystals exhibit rhombohedral(R) → monoclinic(M) → tetragonal(T) → cubic(C) phase transition path. The electrical properties of the PIMNT-Mn single crystals such as the longitudinal electrostrictive coefficient (Q), the converse piezoelectric constant (d33), and the maximum strain value (Smax%) have changed abnormally around the phase transition temperatures (TR-M and TM-T).

Growth and structural characterization of single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) obtained by the partial melting technique

NASA Astrophysics Data System (ADS)

Yamaki, K.; Bamba, Y.; Mochiku, T.; Funahashi, S.; Matsushita, Y.; Irie, A.

2018-05-01

In this study, cubic single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) with typical dimensions of 100-150 μm in length were grown by the partial melting technique. Multiple 00l reflections were first observed by XRD measurements of the bulk RuGd-1212 single crystals. The resistivity of the obtained crystals was roughly estimated to be ∼24-80 mΩ cm and no superconducting transition was observed down to 4.2 K. From the XRD measurements and refinement of the crystal structure, it was apparent that the Ru and Sr sites of the single-crystal RuGd-1212 were partially substituted by Cu and Gd, respectively. Oxygen defects were found to be minor (δ ≈ 0.1). The lattice parameters a and c of the single crystals were found to be larger and smaller, respectively, than those of a polycrystalline sample.

ESR and nonresonant microwave absorption of ErBa2Cu3O(7-delta) and HoBa2Cu3O(7-delta) single crystals

NASA Astrophysics Data System (ADS)

Tagaya, Kimihito; Fukuoka, Nobuo; Nakanishi, Shigemitsu

1990-12-01

ESR measurements were performed for ErBa2Cu3O(7-delta) and HoBa2Cu3O(7-delta) single crystals from 77 K to room temperature. The ESR signals of Er2BaCuO5 and Ho2BaCuO5 were observed, and their temperature variations were investigated. Nonresonant microwave absorption was also observed below the superconducting critical temperature of 93 K. The principal values of lower critical field were determined.

Doping of Czochralski-grown bulk β-Ga2O3 single crystals with Cr, Ce and Al

NASA Astrophysics Data System (ADS)

Galazka, Zbigniew; Ganschow, Steffen; Fiedler, Andreas; Bertram, Rainer; Klimm, Detlef; Irmscher, Klaus; Schewski, Robert; Pietsch, Mike; Albrecht, Martin; Bickermann, Matthias

2018-03-01

We experimentally evaluated segregation of Cr, Ce and Al in bulk β-Ga2O3 single crystals grown by the Czochralski method, as well as the impact of these dopants on optical properties. The segregation of Cr and Ce and their incorporation into the β-Ga2O3 crystal structure strongly depends on O2 concentration in the growth atmosphere which has a noticeable impact on decomposition of Ga2O3 and Cr2O3, as well as on the charge state of Cr and Ce. Effective segregation coefficients for Cr are in the range of 3.1-1.5 at 7-24 vol% O2, while for Ce they are roughly below 0.01 at 1.5-34 vol% O2. The effective segregation coefficient for Al is 1.1 at 1.5-21 vol% O2. Both dopants Ce and Al have a thermodynamically stabilizing effect on β-Ga2O3 crystal growth by supressing decomposition. While Ce has no impact on the optical transmittance in the ultraviolet and visible regions, in Cr doped crystals we observe three absorption bands due to Cr3+ on octahedral Ga sites, one in the ultraviolet merging with the band edge absorption of β-Ga2O3 and two in the visible spectrum, for which we estimate the absorption cross sections. Al doping also does not induce dopant related absorption bands but clearly shifts the absorption edge as one expects for a solid-solution crystal Ga2(1-x)Al2xO3 still in the monoclinic phase. For the highest doping concentration (Ga1.9Al0.1O3) we estimate an increase of the energy gap by 0.11 eV.

High-pressure floating-zone growth of perovskite nickelate LaNiO 3 single crystals

DOE PAGES

Zhang, Junjie; Zheng, Hong; Ren, Yang; ...

2017-04-07

We report the first single crystal growth of the correlated metal LaNiO 3 using a high-pressure optical-image floating zone furnace. The crystals were studied using single crystal/powder X-ray diffraction, resistivity, specific heat, and magnetic susceptibility. The availability of bulk LaNiO 3 crystals will (i) promote deep understanding in this correlated material, including the mechanism of enhanced paramagnetic susceptibility, and (ii) provide rich opportunities as a substrate for thin film growth such as important ferroelectric and/or multiferroic materials. As a result, this study demonstrates the power of high pO 2 single crystal growth of nickelate perovskites and correlated electron oxides moremore » generally.« less

Temperature dependence of luminescence behavior in Er3+-doped BaY2F8 single crystal

NASA Astrophysics Data System (ADS)

Wang, Shuai; Ruan, Yongfeng; Tsuboi, Taiju; Tong, Hongshuang; Wang, Youfa; Zhang, Shouchao

2013-12-01

BaY2F8 single crystals doped with Er3+ ions have been grown by the temperature gradient method. The absorption, excitation and emission spectra for Er3+-doped BaY2F8 crystals were measured at room temperature (297 K) and 12 K. The effect of temperature on the luminescence intensity and effective bandwidth was investigated in the range of 12-297 K. The temperature dependence of the fluorescence intensity ratio (FIR) for the 522 nm emission (2H11/2→4I15/2 transition) and the 552 nm emission (4S3/2→4I15/2 transition) was also studied in the range of 12-297 K. Based on the fitting FIR curve, the value of the constant term B (2.25) was obtained. The fitting FIR curve and FIR equation may have a potential application in the temperature measurement. In addition, the up-conversion spectrum at room temperature was recorded under excitation of 980 nm and the up-conversion mechanism was analyzed in detail.

Scintillation properties of Li6Y0.5Gd0.5(BO3)3: Ce3+ single crystal

NASA Astrophysics Data System (ADS)

Fawad, U.; Rooh, Gul; Kim, H. J.; Park, H.; Kim, Sunghwan; Khan, Sajid

2015-01-01

The Ce3+ doped mixed crystals of Li6Y(BO3)3 and Li6Gd(BO3)3 are grown by Czochralski technique with equal mole ratios of both Yttrium and Gadolinium i.e. Li6Y0.5Gd0.5(BO3)3. The grown crystals have the dimensions of ∅10×30 mm2. Powder X-ray diffraction (XRD) analysis confirmed single phase of the grown crystals. X-ray and laser induced luminescence spectra are presented. Scintillation properties such as energy resolution, light yield, decay time and α/β ratio under the excitation of 137Cs γ-ray photons and 241Am α-particles are also reported in this article.

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.

Scintillation properties of polycrystalline LaxY1-xO3 ceramic

NASA Astrophysics Data System (ADS)

Sahi, Sunil; Chen, Wei; Kenarangui, Rasool

2015-03-01

Scintillators are the material that absorbs the high-energy photons and emits visible photons. Scintillators are commonly used in radiation detector for security, medical imaging, industrial applications and high energy physics research. Two main types of scintillators are inorganic single crystals and organic (plastic or liquid) scintillators. Inorganic single crystals are expensive and difficult to grow in desire shape and size. Also, some efficient inorganic scintillator such as NaI and CsI are not environmental friendly. But on the other hand, organic scintillators have low density and hence poor energy resolution which limits their use in gamma spectroscopy. Polycrystalline ceramic can be a cost effective alternative to expensive inorganic single crystal scintillators. Here we have fabricated La0.2Y1.8O3 ceramic scintillator and studied their luminescence and scintillation properties. Ceramic scintillators were fabricated by vacuum sintering of La0.2Y1.8O3 nanoparticles at temperature below the melting point. La0.2Y1.8O3 ceramic were characterized structurally using XRD and TEM. Photoluminescence and radioluminescence studies were done using UV and X-ray as an excitation source. We have used gamma isotopes with different energy to studies the scintillation properties of La0.2Y1.8O3 scintillator. Preliminary studies of La0.2Y1.8O3 scintillator shows promising result with energy resolution comparable to that of NaI and CsI.

As-Deposited (La1-xSrx)(Ga1-y-zMgyCoz)O3-(x+y+z)/2 Crystallized Thin Films Prepared by Pulsed Laser Deposition for Application to Solid Oxide Fuel Cell Electrolyte

NASA Astrophysics Data System (ADS)

Mitsugi, Fumiaki; Kanazawa, Seiji; Ohkubo, Toshikazu; Nomoto, Yukiharu; Ishihara, Tatsumi; Takita, Yusaku

2004-01-01

Doped lanthanum gallate (La1-xSrx)(Ga1-y-zMgyCoz)O3-(x+y+z)/2 (LSGMCO) perovskite oxide films were deposited on a quartz glass, LaAlO3 single-crystal substrate and porous anode electrode of a solid oxide fuel cell (SOFC) by pulsed laser deposition. It was necessary to increase the substrate temperature up to 800°C for a crystallization of the LSGMCO films. The film deposited on the LaAlO3 single-crystal substrate grew along the c-axis. The as-deposited LSGMCO thick film fabricated on the porous substrate at 800°C and at an oxygen pressure of 20Pa was formed from polycrystal columns and showed a high conductivity of 0.7S/cm at a measurement temperature of 800°C. The activation energies were 0.72 eV at 600-800°C and 1.05 eV at 400-600°C.

Bio-inspired synthesis of Y2O3: Eu3+ red nanophosphor for eco-friendly photocatalysis

NASA Astrophysics Data System (ADS)

Prasanna kumar, J. B.; Ramgopal, G.; Vidya, Y. S.; Anantharaju, K. S.; Daruka Prasad, B.; Sharma, S. C.; Prashantha, S. C.; Premkumar, H. B.; Nagabhushana, H.

2015-04-01

We report the synthesis of Y2O3: Eu3+ (1-11 mol%) nanoparticles (NPs) with different morphologies via eco-friendly, inexpensive and simple low temperature solution combustion method using Aloe Vera gel as fuel. The formation of different morphologies of Y2O3: Eu3+ NPs were characterized by PXRD, SEM, TEM, HRTEM, UV-Visible and PL techniques. The PXRD data and Rietveld analysis confirms the formation of single phase Y2O3 with cubic crystal structure. The influence of Eu3+ ion concentration on the morphology, UV-Visible absorption, PL emission and photocatalytic activity of Y2O3: Eu3+ nanostructures were investigated. Y2O3: Eu3+ NPs exhibit intense red emission with CIE chromaticity coordinates (0.50, 0.47) and correlated color temperature values at different excitation ranges from 1868 to 2600 K. The control of Eu3+ ion on Y2O3 matrix influences the photocatalytic decolorization of methylene blue (MB) as a model compound was evaluated under UVA light. Enhanced photocatalytic activity of conical shaped Y2O3: Eu3+ (1 mol%) was attributed to dopant concentration, crystallite size, textural properties and capability of reducing the electron-hole pair recombination. The trend of inhibitory effect in the presence of different radical scavengers followed the order SO42- > Cl- > C2H5OH > HCO3- > CO32-. These findings show great promise of Y2O3: Eu3+ NPs as a red phosphor in warm white LEDs as well as eco-friendly heterogeneous photocatalysis.

Domain characterization of Pb(Zn1/3Nb2/3)O3-(6%-7%)PbTiO3 single crystals using scanning electron acoustic microscopy

NASA Astrophysics Data System (ADS)

Wong, Meng Fei; Heng, Xiangxin; Zeng, Kaiyang

2008-10-01

Domain structures of [001]T and [011]T-cut Pb(Zn1/3Nb2/3)O3-(6%-7%)PbTiO3 (PZN-PT) single crystals are studied using scanning electron acoustic microscope (SEAM) technique. The observation of the orientation of domain walls agree reasonably well with the trigonometric projection of rhombohedral and orthorhombic dipoles on the (001) and (011) surfaces, respectively. After mechanical loading with microindentation, domain switching is also observed to form a hyperbolic butterfly shape and extend preferentially along four diagonal directions, i.e., ⟨110⟩ on (001) surface and ⟨111¯⟩ on (011) surface. The critical shear stress to cause domain switching for PZN-PT crystal is estimated to be approximately 49 MPa for both {110} and {111¯} planes based on theoretical analysis. Generally, the SEAM technique has been successfully demonstrated to be a valid technique for observation of domain structures in single crystal PZN-PTs.

Flux growth of high-quality CoFe 2O 4 single crystals and their characterization

NASA Astrophysics Data System (ADS)

Wang, W. H.; Ren, X.

2006-04-01

We report the growth of high-quality CoFe 2O 4 single crystals using a borax flux method. The crystals were characterized by powder X-ray diffraction, electron probe microanalysis and Raman spectroscopy. We found the crystals are flux-free and highly homogeneous in composition. X-ray rocking curves of the CoFe 2O 4 single crystals showed a full-width at half-maximum of 0.15°. The saturation magnetization of the CoFe 2O 4 single crystals was measured to be 90 emu/g or equivalently 3.65 μ B/f.u. at 5 K.

Bio-inspired synthesis of Y2O3: Eu(3+) red nanophosphor for eco-friendly photocatalysis.

PubMed

Prasanna kumar, J B; Ramgopal, G; Vidya, Y S; Anantharaju, K S; Daruka Prasad, B; Sharma, S C; Prashantha, S C; Premkumar, H B; Nagabhushana, H

2015-04-15

We report the synthesis of Y2O3: Eu(3+) (1-11 mol%) nanoparticles (NPs) with different morphologies via eco-friendly, inexpensive and simple low temperature solution combustion method using Aloe Vera gel as fuel. The formation of different morphologies of Y2O3: Eu(3+) NPs were characterized by PXRD, SEM, TEM, HRTEM, UV-Visible and PL techniques. The PXRD data and Rietveld analysis confirms the formation of single phase Y2O3 with cubic crystal structure. The influence of Eu(3+) ion concentration on the morphology, UV-Visible absorption, PL emission and photocatalytic activity of Y2O3: Eu(3+) nanostructures were investigated. Y2O3: Eu(3+) NPs exhibit intense red emission with CIE chromaticity coordinates (0.50, 0.47) and correlated color temperature values at different excitation ranges from 1868 to 2600 K. The control of Eu(3+) ion on Y2O3 matrix influences the photocatalytic decolorization of methylene blue (MB) as a model compound was evaluated under UVA light. Enhanced photocatalytic activity of conical shaped Y2O3: Eu(3+) (1 mol%) was attributed to dopant concentration, crystallite size, textural properties and capability of reducing the electron-hole pair recombination. The trend of inhibitory effect in the presence of different radical scavengers followed the order SO4(2-)>Cl(-)>C2H5OH>HCO3(-)>CO3(2-). These findings show great promise of Y2O3: Eu(3+) NPs as a red phosphor in warm white LEDs as well as eco-friendly heterogeneous photocatalysis. Copyright © 2015 Elsevier B.V. All rights reserved.

Optical spectroscopy of low-phonon Ho3+ doped BaY2F8 single crystal

NASA Astrophysics Data System (ADS)

Li, Chun; Zeng, Fanming; Lin, Hai; Zheng, Dongyang; Yang, Xiaodong; Liu, Wang; Liu, Jinghe

2014-12-01

The Ho:BaY2F8 crystal was grown by Czochralski method. The crystal phase structure and absorption spectra were tested, the absorption peak exists near 899 nm, the absorption cross section was 1.27 × 10-21 cm2. The emission spectra of crystals in the vicinity of 2 and 3.9 μm were measured, the 2 μm near infrared light induced by 5I7 → 5I8 transition of Ho3+ ions was observed, as well as the fluorescence output at 3.9 μm (5I5 → 5I6), emission cross section at 3.9 μm was calculated to be 0.86 × 10-21 cm2. We suppose that the Ho:BaY2F8 crystal has a large application prospect for the 2-4 μm wavelength near infrared laser.

Monoclinic MB phase and phase instability in [110] field cooled Pb(Zn1/3Nb2/3)O3-4.5%PbTiO3 single crystals

NASA Astrophysics Data System (ADS)

Yao, Jianjun; Cao, Hu; Ge, Wenwei; Li, Jiefang; Viehland, D.

2009-08-01

We report the finding of a monoclinic MB phase in Pb(Zn1/3Nb2/3)O3-4.5%PbTiO3 single crystals. High precision x-ray diffraction investigations of [110] field cooled crystals have shown a transformation sequence of cubic(C)→tetragonal(T)→orthorhombic(O)→monoclinic(MB), which is different from that previously reported [A.-E. Renault et al., J. Appl. Phys. 97, 044105 (2005)]. Beginning in the zero-field-cooled condition at 383 K, a rhombohedral (R)→MB→O sequence was observed with increasing field. Coexisting MB and O phases were then found upon removal of field, which fully transformed to MB on cooling to room temperature.

Compositional segregation and electrical properties characterization of [001]- and [011]-oriented co-growth Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal

NASA Astrophysics Data System (ADS)

Song, Kexin; Li, Zhenrong; Guo, Haisheng; Xu, Zhuo; Fan, Shiji

2018-04-01

A Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 relaxor ferroelectric single crystal boule of 3 in. diameter was grown using [001]- and [011]-oriented co-growth crystals as seeds by the modified Bridgman method. The as-grown crystal boule was divided into two growth regions [001] and [011]. The composition and the electrical properties of samples of the two regions were characterized in detail along the growth direction in the whole crystal boule. The PT content of [001]-grown samples increased from 27.7 to 36.8 mol. % along the growth direction, especially they are averagely higher about 0.7 mol. % than those of [011]-grown samples at the same growth position. The PMN content of [001]-grown samples decreased from 43.0 to 34.8 mol. %, which is lower than that of the corresponding [011]-grown samples. The compositional segregation behavior along [001] and [011] growth directions was discussed based on the crystal growth theories. Variations in the rhombohedral to tetragonal phase transition temperature (TRT), the piezoelectric properties, the coercive electric field and the remnant polarization of [001] samples were discussed according to changes in compositional segregation and crystal anisotropy. Under the exact same growth conditions, the [011]-grown crystal has a larger composition segregation effect than that of the [001]-grown crystal. This result provides a positive effect on analysing the nature and reducing the effect of compositional segregation.

Intermediate phases in [111]- and [001]-oriented PbMg1/3Nb2/3O3-29PbTiO3 single crystals

NASA Astrophysics Data System (ADS)

Kamzina, L. S.

2017-09-01

Phase transformations in [111]- and [001]-oriented PbMg1/3Nb2/3O3-29PbTiO3 single crystals have been studied using dielectric and optical measurements before and after applying an electric field. It is shown that the subsequence of phase transitions rhombohedral ( R)—tetragonal ( T)—cubic ( C) phases is observed in nonpolarized samples of both orientations as temperature increases. In the [111]-oriented crystal, an additional intermediate monoclinic phase (it is possible, M a ) is induced after preliminary polarization at room temperature and the R- M a - T- C phase transitions are observed on heating. In the [001]-oriented crystal, after its polarization, the monoclinic phase forms instead of the rhombohedral phase even at room temperature and the M a - T- C transitions occur on heating. The results are discussed from the point of view of the existence polar nanoregions with different local symmetries in a glasslike matrix.

Crystal growth and piezoelectric properties of Ca3Ta(Ga0.9Sc0.1)3Si2O14 bulk single crystal

NASA Astrophysics Data System (ADS)

Igarashi, Yu; Yokota, Yuui; Ohashi, Yuji; Inoue, Kenji; Yamaji, Akihiro; Shoji, Yasuhiro; Kamada, Kei; Kurosawa, Shunsuke; Yoshikawa, Akira

2018-03-01

Ca3Ta(Ga0.9Sc0.1)3Si2O14 langasite-type single crystal with a diameter of 1 in. was grown by Czochralski (Cz) method. Obtained crystal had good crystallinity and its lattice constants exceeded those of Ca3TaGa3Si2O14 (CTGS) according to the X-ray analysis. A crack-free specimen cut from the grown crystal was used for the measurements of dielectric constant ε11T/ε0, electromechanical coupling factor k12, and piezoelectric constant d11. The accuracies of these measurements were better than those for the crystal grown by micro-pulling-down (μ-PD) method. Substitution of Ga with Sc resulted modification of these constants in the directions opposite to those observed after partial substitution of Ga (of CTGS) with Al. This suggests that increase of |d14| was most probably associated with enlargement of average size of the Ga sites. The crystal reported here had greater dimensions as compared to analogous crystals grown by the μ-PD method. As a result, accuracy of determination of acoustic constants of this material may be improved.

Reduction of electro-optic half-wave voltage of 0.93Pb(Zn1/3Nb2/3)O3-0.07PbTiO3 single crystal through large piezoelectric strain

PubMed Central

Sun, Enwei; Wang, Zhu; Zhang, Rui; Cao, Wenwu

2011-01-01

The influence of converse piezoelectric effect on the electro-optic coefficient of single domain relaxor-based 0.93Pb(Zn1/3Nb2/3)O3-0.07PbTiO3 (PZN-0.07PT) has been quantified under ambient conditions. It was found that the large piezoelectric constants d31 and d33 have significant influence to the half-wave voltage of electro-optic modulators. For single domain PZN-0.07PT crystal, Vπ13T is reduced by a factor of 8 and Vπ13L can be decreased by more than an order of magnitude due to the large piezoelectric effect. Compared to commonly used electro-optic crystal LiNbO3 and BaTiO3, PZN-xPT single crystal is much superior for optic phase modulation applications because they have much higher linear electro-optic coefficients and much lower half-wave voltage when piezoelectric strain influence is considered. PMID:21308004

Lower critical field measurements in YBa2Cu3O(6+x) single crystals

NASA Technical Reports Server (NTRS)

Kaiser, D. L.; Swartzendruber, L. J.; Gayle, F. W.; Bennett, L. H.

1991-01-01

The temperature dependence of the lower critical field in YBa2Cu3O(6+x) single crystals was determined by magnetization measurements with the applied field parallel and perpendicular to the c-axis. Results are compared with data from the literature and fitted to Ginzberg-Landau equations by assuming a linear dependence of the parameter kappa on temperature. A value of 7 plus or minus 2 kOe was estimated for the thermodynamic critical field at T = O by comparison of calculated H (sub c2) values with experimental data from the literature.

Preparation of a Non-Polar ZnO Film on a Single-Crystal NdGaO3 Substrate by the RF Sputtering Method

NASA Astrophysics Data System (ADS)

Kashiwaba, Y.; Tanaka, Y.; Sakuma, M.; Abe, T.; Imai, Y.; Kawasaki, K.; Nakagawa, A.; Niikura, I.; Kashiwaba, Y.; Osada, H.

2018-04-01

Preparation of non-polar ZnO ( 11\\overline{2} 0 ) films on single-crystal NdGaO3 (NGO) (001) substrates was successfully achieved by the radio frequency (RF) sputtering method. Orientation, deposition rate, and surface roughness of ZnO films strongly depend on the working pressure. Characteristics of ZnO films deposited on single-crystal NGO (001) substrates were compared with those of ZnO films deposited on single-crystal sapphire ( 01\\overline{1} 2 ) substrates. An x-ray diffraction peak of the ZnO ( 11\\overline{2} 0 ) plane was observed on ZnO films deposited on single-crystal NGO (001) substrates under working pressure of less than 0.5 Pa. On the other hand, uniaxially oriented ZnO ( 11\\overline{2} 0 ) films on single-crystal sapphire ( 01\\overline{1} 2 ) substrates were observed under working pressure of 0.1 Pa. The mechanism by which the diffraction angle of the ZnO ( 11\\overline{2} 0 ) plane on single-crystal NGO (001) substrates was shifted is discussed on the basis of anisotropic stress of lattice mismatch. The deposition rate of ZnO films decreased with an increase in working pressure, and the deposition rate on single-crystal NGO (001) substrates was larger than that on single-crystal sapphire ( 01\\overline{1} 2 ) substrates. Root mean square (RMS) roughness of ZnO films increased with an increase in working pressure, and RMS roughness of ZnO films on single-crystal NGO (001) substrates was smaller than that of ZnO films on single-crystal sapphire ( 01\\overline{1} 2 ) substrates even though the film thickness on single-crystal NGO (001) substrates was greater than that on sapphire substrates. It is thought that a single-crystal NGO (001) substrate is useful for deposition of non-polar ZnO ( 11\\overline{2} 0 ) films.

Growth and characterization of β-Ga2O3 crystals

NASA Astrophysics Data System (ADS)

Nikolaev, V. I.; Maslov, V.; Stepanov, S. I.; Pechnikov, A. I.; Krymov, V.; Nikitina, I. P.; Guzilova, L. I.; Bougrov, V. E.; Romanov, A. E.

2017-01-01

Here we report on the growth and characterization of β-Ga2O3 bulk crystals and polycrystalline layer on different substrates. Bulk β-Ga2O3 crystals were produced by free crystallisation of gallium oxide melt in sapphire crucible. Transparent single crystals measuring up to 8 mm across were obtained. Good structural quality was confirmed by x-ray diffraction rocking curve FWHM values of 46″. Young's modulus, shear modulus and hardness of the β-Ga2O3 crystals were measured by nanoindentation and Vickers microindentation techniques. Polycrystalline β-Ga2O3 films were deposited on silicon and sapphire substrates by sublimation method. It was found that structure and morphology of the films were greatly influenced by the material and orientation of the substrates. The best results were achieved on a-plane sapphire substrates where predominantly (111) oriented films were obtained.

Pinning-to-barrier crossover in YBa2Cu3O7-δ single crystals

NASA Astrophysics Data System (ADS)

Indenbom, M. V.; van der Beek, C. J.; Berseth, V.; Konczykowski, M.; Holtzberg, F.; Benoit, W.

1996-03-01

The behaviour of magnetic flux in high purity untwinned YBa2Cu3O7-δ (YBCO) single crystals is visualised by means of the magneto-optical technique. It is observed that after zero field-cooling at high temperatures near T c , flux penetrates directly to the sample center over a flux free edge area, in contrast to the usual Bean-like flux penetration from the edges. This fact clearly shows that volume pinning becomes negligible compared with the edge barrier. The role of the recently rediscovered geometrical barrier in the crystal magnetisation is discussed.

Characterizing the residual glass in a MgO/Al2O3/SiO2/ZrO2/Y2O3 glass-ceramic

PubMed Central

Seidel, Sabrina; Patzig, Christian; Wisniewski, Wolfgang; Gawronski, Antje; Hu, Yongfeng; Höche, Thomas; Rüssel, Christian

2016-01-01

The non-isochemical crystallization of glasses leads to glass-ceramics in which the chemical composition of the amorphous matrix differs from that of the parent glass. It is challenging to solely analyse the properties of these residual glassy phases because they frequently contain finely dispersed crystals. In this study, the composition of the residual glass matrix after the crystallization of a glass with the mol% composition 50.6 SiO2 · 20.7 MgO · 20.7 Al2O3 · 5.6 ZrO2 · 2.4 Y2O3 is analysed by scanning transmission electron microscopy (STEM) including energy dispersive X-ray analysis (EDXS). A batch of the residual glass with the determined composition is subsequently melted and selected properties are analysed. Furthermore, the crystallization behaviour of this residual glass is studied by X-ray diffraction, scanning electron microscopy including electron backscatter diffraction and STEM-EDXS analyses. The residual glass shows sole surface crystallization of indialite and multiple yttrium silicates while bulk nucleation does not occur. This is in contrast to the crystallization behaviour of the parent glass, in which a predominant bulk nucleation of spinel and ZrO2 is observed. The crystallization of the residual glass probably leads to different crystalline phases when it is in contact to air, rather than when it is enclosed within the microstructure of the parent glass-ceramics. PMID:27734918

Fabrication of Al2O3 coated 2D TiO2 nanoparticle photonic crystal layers by reverse nano-imprint lithography and plasma enhanced atomic layer deposition.

PubMed

Kim, Ki-Kang; Ko, Ki-Young; Ahn, Jinho

2013-10-01

This paper reports simple process to enhance the extraction efficiency of photoluminescence (PL) from Eu-doped yttrium oxide (Y2O3:Eu3+) thin-film phosphor (TFP). Two-dimensional (2D) photonic crystal layer (PCL) was fabricated on Y2O3:Eu3+ phosphor films by reverse nano-imprint method using TiO2 nanoparticle solution as a nano-imprint resin and a 2D hole-patterned PDMS stamp. Atomic scale controlled Al2O3 deposition was performed onto this 2D nanoparticle PCL for the optimization of the photonic crystal pattern size and stabilization of TiO2 nanoparticle column structure. As a result, the light extraction efficiency of the Y2O3:Eu3+ phosphor film was improved by 2.0 times compared to the conventional Y2O3:Eu3+ phosphor film.

Generation and characterization of point defects in SrTiO3 and Y3Al5O12

NASA Astrophysics Data System (ADS)

Selim, F. A.; Winarski, D.; Varney, C. R.; Tarun, M. C.; Ji, Jianfeng; McCluskey, M. D.

Positron annihilation lifetime spectroscopy (PALS) was applied to characterize point defects in single crystals of Y3Al5O12 and SrTiO3 after populating different types of defects by relevant thermal treatments. In SrTiO3, PALS measurements identified Sr vacancy, Ti vacancy, vacancy complexes of Ti-O (vacancy) and hydrogen complex defects. In Y3Al5O12 single crystals the measurements showed the presence of Al-vacancy, (Al-O) vacancy and Al-vacancy passivated by hydrogen. These defects are shown to play the major role in defining the electronic and optical properties of these complex oxides.

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

NASA Astrophysics Data System (ADS)

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

2016-01-01

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

Growth and electrical transport properties of La 0.7 Sr 0.3 MnO 3 thin films on Sr 2 IrO 4 single crystals

DOE PAGES

Moon, E. J.; May, A. F.; Shafer, P.; ...

2017-04-20

Here, we report the physical properties of La 0.7 Sr 0.3 MnO 3 thin films on Sr 2 IrO 4 single crystals. We also deposited the manganite films using oxide molecular beam epitaxy on flux-grown (001)-oriented iridate crystals. Temperature-dependent magnetotransport and x-ray magnetic circular dichroism measurements reveal the presence of a ferromagnetic metallic ground state in the films, consistent with films grown on SrTiO 3 and La 0.3 Sr 0.7 Al 0.65 Ta 0.35 O 3 . A parallel resistance model is used to separate conduction effects within the Sr 2 IrO 4 substrate and the La 0.7 Sr 0.3more » MnO 3 thin films, revealing that the measured resistance maximum does not correspond to the manganite Curie temperature but results from a convolution of properties of the near-insulating substrate and metallic film. Furthermore, the ability to grow and characterize epitaxial perovskites on Sr 2 IrO 4 crystals enables a new route for studying magnetism at oxide interfaces in the presence of strong spin-orbit interactions.« less

X-ray induced luminescence properties of (Y,Eu)AlO3 single crystals

NASA Astrophysics Data System (ADS)

Kuro, Tomoaki; Nakauchi, Daisuke; Okada, Go; Kawaguchi, Noriaki; Yanagida, Takayuki

2017-02-01

We investigated photoluminescence, scintillation and dosimeter properties of (Y1-x Eux)AlO3 (x = 0.001, 0.5 and 1) single crystals (hereafter denoted as Eu:YAP for x = 0.001, EYAP for x = 0.5 and EAP for x = 1). The samples were prepared by the Floating Zone method. In photoluminescence (PL), we observed a broad emission around 300-400 nm due to host under excitation of 280 nm, and emissions due to the 4f state transitions of Eu3+ appeared around 590 nm and 615 nm. Scintillation spectra also show emission peaks around 590 and 615 nm due to the 4f state transitions of Eu3+ in all the samples. In addition, emissions around 300-400 nm due to YAP host and around 550-700 nm due to 5d-4f transitions of Eu2+ appeared in Eu:YAP. The PL and scintillation decay time profiles consisted of several exponential decay components. The fast (ns) component group was possibly due to host emission, and especially Eu:YAP demonstrated a very fast PL decay time of 16 ns. The intermediate (μs) component group was due to the 5d-4f transitions of Eu2+. The slow (ms) component group was ascribed to the 4f state transitions of Eu3+ ion. The Eu:YAP sample showed intense thermally-stimulated luminescence (TSL) with peaks at 46, 155, 255 and 443 °C. The intensity was much higher than those of EAP and EYAP. In particular, the peak at 254 °C, which showed the highest intensity, was due to doping with Eu. The TSL dose response function showed a good linearity (R2 > 0.99) over a wide dose range from 0.1 mGy to 100 mGy for Eu:YAP, which showed the highest sensitivity among the present samples.

Ultrasound synthesis of Y2O3: Dy3+ nanophosphor: Structural and photometric properties suitable for wLEDs

NASA Astrophysics Data System (ADS)

Marappa, B.; Rudresha, M. S.; Nagabhsuhana, H.; Basavaraj, R. B.; Prasad, B. Daruka

2017-05-01

The facile ultrasound synthesis of Y2O3:Dy3+ nanostructures by using bio-surfactant mimosa pudica leaves extract. The concentration of bio-surfactant was the key factor in controlling the morphology of Y2O3 nanostructures. The formation of different morphologies of Y2O3: Dy3+ was characterized by SEM, TEM and HRTEM. The PXRD data and Rietveld analysis evident the formation of single phase Y2O3 with cubic crystal structure. The influence of Dy3+ concentration on the structure morphology, UV absorption, and PL emission of Y2O3: Dy3+ nanostructures were investigated systematically. Y2O3: Dy3+ exhibits intense warm white emission with CIE chromaticity coordinates (0.32, 0.33) and CCT value is 5525 K which corresponds to vertical day light. SEM micrographs showed superstructure morphology influenced by both sonication time as well as surfactant concentration. Pl emission spectra shows three intense peaks observed at 480, 574 and 666 nm attributed to the Dy3+ transitions. The photometric properties were studied by evaluating the CIE, CCT diagrams and the results were very fruitful in making the white light emitting diodes. This method has been considered to be the cost effective and eco-friendly to synthesize nanomaterials with superior morphology suitable for display device applications.

Dielectric and domain studies on Fe doped KNbO3 single crystal

NASA Astrophysics Data System (ADS)

Shamkuwar, Sanjaykumar H.; Patil, Naresh M.; Korde, Vivek B.; Pradnyakar, Namrata V.

2018-05-01

Synthesis of Fe doped KNbO3 single crystals by flux method is reported here. The effect of Fe-doping on phase transition temperatures of KNbO3 single crystals was investigated using dielectric studies. The phase transition temperatures were found to be 225°C and 425°C which almost same as reported by others. The domain studies were carried out using metallurgical microscope and it shows the presence of 60° and 90° domains in the grown crystals.

Dependences of the density of M{sub 1-x}R{sub x}F{sub 2+x} and R{sub 1-y}M{sub y}F{sub 3-y} single crystals (M = Ca, Sr, Ba, Cd, Pb; R means rare earth elements) on composition

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

Sorokin, N. I., E-mail: sorokin@ns.crys.ras.ru; Krivandina, E. A.; Zhmurova, Z. I.

2013-11-15

The density of single crystals of nonstoichiometric phases Ba{sub 1-x}La{sub x}F{sub 2+x} (0 {<=} x {<=} 0.5) and Sr{sub 0.8}La{sub 0.2-x}Lu{sub x}F{sub 2.2} (0 {<=} x {<=} 0.2) with the fluorite (CaF{sub 2}) structure type and R{sub 1-y}Sr{sub y}F{sub 3-y} (R = Pr, Nd; 0 {<=} y {<=} 0.15) with the tysonite (LaF{sub 3}) structure type has been measured. Single crystals were grown from a melt by the Bridgman method. The measured concentration dependences of single crystal density are linear. The interstitial and vacancy models of defect formation in the fluorite and tysonite phases, respectively, are confirmed. To implement themore » composition control of single crystals of superionic conductors M{sub 1-x}R{sub x}F{sub 2+x} and R{sub 1-y}M{sub y}F{sub 3-y} in practice, calibration graphs of X-ray density in the MF{sub 2}-RF{sub 3} systems (M = Ca, Sr, Ba, Cd, Pb; R = La-Lu, Y) are plotted.« less

Electrochemical preparation of single-crystalline Cr 2O 3 from molten salts

NASA Astrophysics Data System (ADS)

Abe, Hideki; Nishida, Kenji; Imai, Motoharu; Kitazawa, Hideaki

2004-06-01

Single crystals of Cr 2O 3 have been grown by means of electrolysis on a 1:100 stoichiometric mixture of CrO 3 and cesium molybdate, Cs 2MoO 4, fused at 1000°C in an ambient atmosphere. Potentiometric measurements on the molten salts have shown the existence of a critical voltage of -320 mV below which hexagonal platelets-shaped single-crystalline Cr 2O 3 is grown on the surface of the working electrode. Coulometry measurements have revealed that the Cr ions are at their highest oxidation state of Cr +6 in the molten electrolyte, which suggests that the electric reduction of Cr +6 to Cr +3 drives the single-crystal growth of Cr 2O 3.

[Preparation and photoluminescence study of Er3+ : Y2O3 transparent ceramics].

PubMed

Luo, Jun-ming; Li, Yong-xiu; Deng, Li-ping

2008-10-01

Y2O3 acted as the matrix material, which was doped with different concentrations of Er3+, Er3+ : Y2O3 nanocrystalline powder was prepared by co-precipitation method, and Er3+ : Y2O3 transparent ceramics was fabricated by vacuum sintering at 1700 degrees C, 1 x 10(-3) Pa for 8 h. By using the X-ray diffraction (D/MAX-RB), transmission electron microscopy(Philips EM420), automatic logging spectrophotometer(DMR-22), fluorescence analyzer (F-4500) and 980 nm diode laser, the structural, morphological and luminescence properties of the sample were investigated. The results show that Er3+ dissolved completely in the Y2O3 cubic phase, the precursor was amorphous, weak diffraction peaks appeared after calcination at 400 degrees C, and if calcined at 700 degrees C, the precursor turned to pure cubic phase. With increasing the calcining temperature, the diffraction peaks became sharp quickly, and when the calcining temperature reached 1100 degrees C, the diffraction peaks became very sharp, indicating that the grains were very large. The particles of Er+ : Y2O3 is homogeneous and nearly spherical, the average diameter of the particles is in the range of 40-60 nm after being calcined at 1000 degrees C for 2 h. The relative density of Er3+ : Y2O3 transparent ceramics is 99.8%, the transmittance of the Er2+ : Y2O3 transparent ceramics is markedly lower than the single crystal at the short wavelength, but the transmittance is improved noticeably with increasing the wavelength, and the transmittance exceeds 60% at the wavelength of 1200 nm. Excited under the 980 nm diode laser, there are two main up-conversion emission bands, green emission centers at 562 nm and red emission centers at 660 nm, which correspond to (4)S(3/2) / (2)H(11/2) - (4)I(15/2) and (4)F(9/2) - (4)I(15/2) radiative transitions respectively. By changing the doping concentrations of Er3+, the color of up-conversion luminescence can be tuned from green to red gradually. The luminescence intensity is not reinforce

Optical Properties of LiNbO3 Single Crystal Grown by Czochralski Method

NASA Astrophysics Data System (ADS)

Sahar, M. R.; Naim, N. M.; Hamzah, K.

2011-03-01

Pure LiNbO3 single crystal was grown by Czochralski method using Automatic Diameter Control—Crystal Growth System (ADC-CGS). The transmission spectrum was determined by using Infrared Spectroscopy while the refractive index was determined using UV-Vis spectroscopy via the Sellmeier equation. The density was also measured using the Archimedes principle. It was found that the peak for the absorption vibrational spectrum for LiNbO3 crystal occurs at 801 cm-1, 672 cm-1, 639 cm-1 and 435 cm-1. The refractive index, ne was found to be 2.480 and the crystal density was around 4.64 g/cm3.

High-quality single crystal growth and magnetic property of Mn4Ta2O9

NASA Astrophysics Data System (ADS)

Cao, Yiming; Xu, Kun; Yang, Ya; Yang, Wangfan; Zhang, Yuanlei; Kang, Yanru; He, Xijia; Zheng, Anmin; Liu, Mian; Wei, Shengxian; Li, Zhe; Cao, Shixun

2018-06-01

A large-size single crystal of Mn4Ta2O9 with ∼3.5 mm in diameter and ∼65 mm in length was successfully grown for the first time by a newly designed one-step method based on the optical floating zone technique. Both the clear Laue spots and sharp XRD Bragg reflections suggest the high quality of the single crystal. In Mn4Ta2O9 single crystal, an antiferromagnetic phase transition was observed below Néel temperature 102 K along c axis, which is similar to the isostructural compound Mn4Nb2O9, but differs from the isostructural Co4Nb2O9. Relative dielectric constant at 30 kOe suggests that no magnetoelectric coupling exists in Mn4Ta2O9.

Menzerite-(Y) a New Species {(Y REE)(Ca Fe2plus)2}[(Mg Fe2plus)(Fe3plus Al)](Si3)O12 from a Felsic Granulite Parry Sound Ontario and a New Garnet End-member (Y2Ca)Mg2(SiO4)3

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

E Grew; J Marsh; M Yates

2011-12-31

Menzerite-(Y), a new mineral species, forms reddish brown cores, n = 1.844 (20), up to 70 {micro}m across, rimmed successively by euhedral almandine containing up to 2.7 wt% Y{sub 2}O{sub 3} and by K-feldspar in a felsic granulite on Bonnet Island in the interior Parry Sound domain, Grenville Orogenic Province, Canada. It is named after Georg Menzer (1897-1989), the German crystallographer who solved the crystal structure of garnet. Single-crystal X-ray-diffraction results yielded space group Ia3d, a = 11.9947(6) {angstrom}. An electron-microprobe analysis of the grain richest in Y (16.93 wt% Y{sub 2}O{sub 3}) gave the following formula, normalized to eightmore » cations and 12 oxygen atoms: {l_brace}Y{sub 0.83}Gd{sub 0.01}Dy{sub 0.05}Ho{sub 0.02}Er{sub 0.07}Tm{sub 0.01}Yb{sub 0.06}Lu{sub 0.02}Ca{sub 1.37}Fe{sub 0.49}{sup 2+}Mn{sub 0.07}{r_brace} [Mg{sub 0.55}Fe{sub 0.42}{sup 2+}Fe{sub 0.58}{sup 3+}Al{sub 0.35} V{sub 0.01}Sc{sub 0.01}Ti{sub 0.08}](Si{sub 2.82}Al{sub 0.18})O{sub 12}, or {l_brace}(Y,REE)(Ca,Fe{sup 2+}){sub 2}{r_brace}[(Mg,Fe{sup 2+})(Fe{sup 3+},Al)](Si{sub 3})O{sub 12}. Synchrotron micro-XANES data gave Fe{sup 3+}/{Sigma}Fe = 0.56(10) versus 0.39(2) calculated from stoichiometry. The scattering power refined at the octahedral Y site, 17.68 epfu, indicates that a relatively light element contributes to its occupancy. Magnesium, as determined by electron-microprobe analyses, would be a proper candidate. In addition, considering the complex occupancy of this site, the average Y-O bond length of 2.0244(16) {angstrom} is in accord with a partial occupancy by Mg. The dominance of divalent cations with Mg > Fe{sup 2+} and the absence of Si at the octahedral Y site (in square brackets) are the primary criteria for distinguishing menzerite-(Y) from other silicate garnet species; the menzerite-(Y) end-member is {l_brace}Y{sub 2}Ca{r_brace}[Mg{sub 2}](Si{sub 3})O{sub 12}. The contacts of menzerite-(Y) with almandine are generally sharp and, in places, cuspate

Single crystal synthesis and magnetism of the Ba Ln 2O 4 family ( Ln = lanthanide)

DOE PAGES

Besara, Tiglet; Lundberg, Matthew S.; Sun, Jifeng; ...

2014-05-27

The series of compounds in the Ba Ln 2O 4 family (Ln = La–Lu, Y) has been synthesized for the first time in single crystalline form, using a molten metal flux. The series crystallizes in the CaV 2O 4 structure type with primitive orthorhombic symmetry (space group Pnma, #62), and a complete structural study of atomic positions, bonds, angles, and distortions across the lanthanide series is presented. With the exception of the Y, La, Eu, and Lu members, magnetic susceptibility measurements were performed between 2 K and 300 K. BaCe 2O 4 and BaYb 2O 4 display large crystal fieldsmore » effects and suppression of magnetic ordering. As a result, all compounds show signs of magnetic frustration due to the trigonal arrangements of the trivalent lanthanide cations in the structure.« less

Scintillation and optical properties of Sn-doped Ga2O3 single crystals

NASA Astrophysics Data System (ADS)

Usui, Yuki; Nakauchi, Daisuke; Kawano, Naoki; Okada, Go; Kawaguchi, Noriaki; Yanagida, Takayuki

2018-06-01

Sn-doped Ga2O3 single crystals were synthesized by the Floating Zone (FZ) method. In photoluminescence (PL) under the excitation wavelength of 280 nm, we observed two types of luminescence: (1) defect luminescence due to recombination of the donor/acceptor pairs which appears at 430 nm and (2) the nsnp-ns2 transitions of Sn2+ which appear at 530 nm. The PL and scintillation decay time curves of the Sn-doped samples were approximated by a sum of exponential decay functions. The faster two components were ascribed to the defect luminescence, and the slowest component was owing to the nsnp-ns2 transitions. In the pulse height spectrum measurements under 241Am α-rays irradiation, all the Sn-doped Ga2O3 samples were confirmed to show a full energy absorption peak but the undoped one. Among the present samples, the 1% Sn-doped sample exhibited the highest scintillation light yield (1,500 ± 150 ph/5.5 MeV-α).

Depoling and fatigue behavior of Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal at megahertz frequencies under bipolar electric field

NASA Astrophysics Data System (ADS)

Chen, Zhaojiang; Li, Shiyang; Zhang, Yang; Cao, Wenwu

2017-05-01

Bipolar electric field induced degradation in [001]c poled Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (PMN-0.29PT) single crystals was investigated at megahertz frequencies. The electromechanical coupling factor kt, dielectric constant ɛr, dielectric loss D, and piezoelectric constant d33 were measured as a function of amplitude, frequency, and number of cycles of the applied electric field. Our results showed that samples degrade rapidly when the field amplitude is larger than a critical value due to the onset of domain switching. We define this critical value as the effective coercive field Ec at high frequencies, which increases drastically with frequency. We also demonstrate an effective counter-depoling method by using a dc bias, which could help the design of high field driven devices based on PMN-PT single crystals and operated at megahertz frequencies.

Investigation on growth and macro-defects of Er3+-doped BaY2F8 laser crystal

NASA Astrophysics Data System (ADS)

Wang, Shuai; Ruan, Yongfeng; Tsuboi, Taiju; Zhang, Shouchao; Wang, Youfa; Tong, Hongshuang

2013-08-01

Large BaY2F8 and Er3+-doped BaY2F8 single crystals were grown by the temperature gradient method. Three kinds of macro-defects were found in BaY2F8 single crystals. These macro-defects include cracks, growth striations and straight pipes. The morphologies and distribution regularities of these macro-defects were observed and studied using a solid polarization microscope. The formation mechanisms and the methods of eliminating these defects were discussed.

Preparation of single-crystal spherical γ-Mo2N by temperature-programmed reaction between β-MoO3 and NH3

NASA Astrophysics Data System (ADS)

Wang, Lu; Zhang, Guo-Hua; Chou, Kuo-Chih

2017-10-01

In the present wok, single-crystalline spherical γ-Mo2N powders was successfully prepared by the temperature-programmed reaction of single-crystal spherical β-MoO3 with NH3 in the temperature ranges of 1013-1073 K. Herein, the Mo source used was monoclinic system, β-MoO3, a metastable phase of MoO3. It is found that the characterizations of the as-prepared γ-Mo2N powders are strongly depended on the selection of the MoO3 precursor. In other words, the as-prepared γ-Mo2N powders inherited the shape, size and structure of the used β-MoO3 precursors upon reaction with NH3. In order to make a comparison, β-MoO3 was also reduced by the mixed gases of N2 and H2 with the flow rate ratio of 1:3 at the identical conditions. It was found that pure β-Mo2N polycrystalline can be obtained when the temperature was 1013 K; while further increasing the reaction temperature, metal Mo powder will be turned up.

Y{sub 2}MoSe{sub 3}O{sub 12} and Y{sub 2}MoTe{sub 3}O{sub 12}: Solid-state synthesis, structure determination, and characterization of two new quaternary mixed metal oxides containing asymmetric coordination environment

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

Bang, Seong-eun; Pan, Zhi; Kim, Yeong Hun

Two new quaternary yttrium molybdenum selenium/tellurium oxides, Y{sub 2}MoSe{sub 3}O{sub 12} and Y{sub 2}MoTe{sub 3}O{sub 12} have been prepared by standard solid-state reactions using Y{sub 2}O{sub 3}, MoO{sub 3}, and SeO{sub 2} (or TeO{sub 2}) as reagents. Single-crystal X-ray diffraction was used to determine the crystal structures of the reported materials. Although both of the materials contain second-order Jahn–Teller (SOJT) distortive cations and are stoichiometrically similar, they reveal different structural features: while Y{sub 2}MoSe{sub 3}O{sub 12} shows a three-dimensional framework consisting of YO{sub 8}, MoO{sub 6}, and SeO{sub 3} groups, Y{sub 2}MoTe{sub 3}O{sub 12} exhibits a layered structure composed ofmore » YO{sub 8}, MoO{sub 4}, TeO{sub 3}, and TeO{sub 4} polyhedra. With the Mo{sup 6+} cations in Y{sub 2}MoSe{sub 3}O{sub 12}, a C{sub 3}-type intraoctahedral distortion toward a face is observed, in which the direction of the out-of-center distortion for Mo{sup 6+} is away from the oxide ligand linked to a Se{sup 4+} cation. The Se{sup 4+} and Te{sup 4+} cations in both materials are in asymmetric coordination environment attributed to the lone pairs. Elemental analyses, infrared spectroscopy, thermal analyses, intraoctahedral distortions, and dipole moment calculations for the compounds are also presented. - Graphical abstract: Y{sub 2}MoSe{sub 3}O{sub 12} reveals a three-dimensional framework consisting of YO{sub 8}, MoO{sub 6}, and SeO{sub 3} polyhedra, whereas Y{sub 2}MoTe{sub 3}O{sub 12} exhibits a layered structure composed of YO{sub 8}, MoO{sub 4}, TeO{sub 3}, and TeO{sub 4} groups. - Highlights: • Two new selenite and tellurite (Y{sub 2}MoQ{sub 3}O{sub 12}; Q=Se and Te) are synthesized. • Y{sub 2}MoQ{sub 3}O{sub 12} contain second-order Jahn–Teller distortive cations in asymmetric environments. • The intra-octahedral distortion of the Mo{sup 6+} is influenced by the Se{sup 4+}.« less

Synthesis, crystal structure, and thermal behavior of the rare earth sulfates (H{sub 5}O{sub 2})M(SO{sub 4}){sub 2} (M = Ho, Er, Y)

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

Wickleder, M.S.

1998-10-01

The compounds (H{sub 5}O{sub 2})M(SO{sub 4}){sub 2} (M = Ho, Er, Y) were obtained from the metal oxides M{sub 2}O{sub 3} (M = Ho, Er,m Y) using diluted sulfuric acid (80%). The crystal structure of the isotypic compounds has been determined from single-crystal data by direct and Fourier methods. The characteristic feature of the crystal structure is a network of edge-sharing [MO{sub 8}] trigon dodecahedra and [SO{sub 4}] tetrahedra providing channels along [111] which are occupied by disordered H{sub 5}O{sub 2}{sup +} ions. In situ X-ray powder investigations exhibit that the compounds are also formed as intermediate phases during themore » reaction of the hydrogen sulfates M(HSO{sub 4}){sub 3} (M = Ho, Er, Y) with water. According to DSC measurements and temperature-dependent powder diffraction studies, the thermal decomposition of the title compounds follows a two-step mechanism. Around 150 C, two molecules of water are driven off, yielding M(HSO{sub 4})(SO{sub 4}) (M = Ho, Er, Y), and finally, at 320 C, H{sub 2}SO{sub 4} (H{sub 2}O + SO{sub 3}) is released to give the anhydrous sulfates M{sub 2}(SO{sub 4}){sub 3}.« less

Optical study of Tm-doped solid solution (Sc0.5Y0.5)2SiO5 crystal

NASA Astrophysics Data System (ADS)

Shi, Jiaojiao; Liu, Bin; Zheng, Lihe; Wang, Qingguo; Tang, Huili; Liu, Junfang; Su, Liangbi; Wu, Feng; Zhao, Hengyu; He, Nuotian; Li, Na; Li, Qiu; Guo, Chao; Xu, Jun; Yang, Kejian; Xu, Xiaodong; Ryba-Romanowski, Witold; Lisiecki, Radosław; Solarz, Piotr

2018-04-01

Tm-doped (Sc0.5Y0.5)2SiO5 (SYSO) crystals were grown by Czochralski method. The UV-VIR-NIR absorption spectra and the near-infrared emission spectra were measured and analysed by the Judd-Ofelt approach. Temperature influence on both absorption and emission spectra has been determined from the data recorded at room temperature and 10 K. It has been found that the structural disorder resulting from dissimilar ionic radii of Sc3+ and Y3+ in the solid solution (Sc0.5Y0.5)2SiO5 crystal brings about a strong inhomogeneous broadening of Tm3+ ions spectra. However, it affects the excited state relaxation dynamics inherent to thulium-doped Y2SiO5 and Sc2SiO5 hosts weakly.

Local strain heterogeneity and elastic relaxation dynamics associated with relaxor behavior in the single-crystal perovskite Pb (I n1 /2N b1 /2 ) O3-PbZr O3-Pb (M g1 /3N b2 /3 ) O3-PbTi O3

NASA Astrophysics Data System (ADS)

He, Wenhui; Carpenter, Michael A.; Lampronti, Giulio I.; Li, Qiang; Yan, Qingfeng

2017-10-01

Recently, Pb (In1/2Nb1/2 ) O3-PbZr O3-Pb (Mg1/3Nb2/3 ) O3-PbTiO3 (PIN-PZ-PMN-PT) relaxor single crystals were demonstrated to possess improved temperature-insensitive properties, which would be desirable for high-power device applications. The relaxor character associated with the development of local random fields (RFs) and a high rhombohedral-tetragonal (R-T) ferroelectric transition temperature (TR-T>120°C) would be critical for the excellent properties. A significant effect of the chemical substitution of In3+ and Zr4+ in PMN-PT to give PIN-PZ-PMN-PT is the development of local strain heterogeneity, which acts to suppress the development of macroscopic shear strains without suppressing the development of local ferroelectric moments and contribute substantially to the RFs in PIN-PZ-PMN-PT. Measurements of elastic and anelastic properties by resonant ultrasound spectroscopy show that PIN-PZ-PMN-PT crystal has a quite different form of elastic anomaly due to Vogel-Fulcher freezing, rather than the a discrete cubic-T transition seen in a single crystal of PMN-28PT. It also has high acoustic loss of the relaxor phase down to TR-T. Analysis of piezoresponse force microscopy phase images at different temperatures provides a quantitative insight into the extent to which the RFs influence the microdomain structure and the short-range order correlation length 〈ξ 〉 .

Effect of Ge-GeO2 co-doping on non-ohmic behaviour of TiO2-V2O5-Y2O3 varistor ceramics

NASA Astrophysics Data System (ADS)

Kunyong, Kang; Guoyou, Gan; Jikang, Yan; Jianhong, Yi; Jiamin, Zhang; Jinghong, Du; Wenchao, Zhao; Xuequan, Rong

2015-07-01

An investigation was made into the effect of doping with the elemental crystal Ge or/and GeO2 on the TiO2-V2O5-Y2O3 varistor ceramics. The result shows that as the doping contents of V2O5 and Y2O3 are 0.5 mol%, respectively, co-doping with 0.3 mol% Ge and 0.9 mol% GeO2 makes the highest α value (α = 12.8), the lowest breakdown voltage V1mA (V1mA = 15.8 V/mm) and the highest grain boundary barrier ΦB (ΦB = 1.48 eV), which is remarkably superior to the TiO2-V2O5-Y2O3 varistor ceramics undoped with Ge and GeO2 and mono-doped with Ge or GeO2. The TiO2-V2O5-Y2O3-Ge-GeO2 ceramic has the prospect of becoming a novel varistor ceramic with excellent electrical properties. Project supported by the National Natural Science Foundation of China (Nos. 51262017, 51362017).

Magnetic and crystal structures of the honeycomb lattice Na2IrO3 and single layer Sr2IrO4

NASA Astrophysics Data System (ADS)

Ye, Feng

2013-03-01

5 d based iridates have recently attracted great attention due to the large spin-orbit coupling (SOC). It is now recognized that the SOC that competes with other relevant energies, particularly the on-site Coulomb interaction U, and have driven novel electronic and magnetic phases. Combining single crystal neutron and x-ray diffractions, we have investigated the magnetic and crystal structures of the honeycomb lattice Na2IrO3. The system orders magnetically below 18.1 K with Ir4+ ions forming zigzag spin chains within the layered honeycomb network with ordered moment of 0.22 μB /Ir site. Such a configuration sharply contrasts the Neel or stripe states proposed in the Kitaev-Heisenberg model. The structure refinement reveals that the Ir atoms form nearly ideal 2D honeycomb lattice while the IrO6 octahedra experience a trigonal distortion that is critical to the ground state. The results of this study provide much-needed experimental insights into the magnetic and crystal structure crucial to the understanding of the exotic magnetic order and possible topological characteristics in the 5 d-electron based honeycomb lattice. Neutron diffraction experiments are also performed to investigate the magnetic and crystal structure of the single layer iridate Sr2IrO4, where new structural information and spin order are obtained that is not available from previous neutron powder diffraction measurement. This work was sponsored in part by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy.

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

Brownmillerite Ca 2 Co 2 O 5 : Synthesis, Stability, and Re-entrant Single Crystal to Single Crystal Structural Transitions

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

Zhang, Junjie; Zheng, Hong; Malliakas, Christos D.

2014-11-20

We synthesized Ca 2Co 2O 5 in the brownmillerite form using a high-pressure optical-image floating zone furnace, and single crystals with dimensions up to 1.4×0.8×0.5 mm 3 were obtained. At room temperature, Ca 2Co 2O 5 crystallizes as a fully ordered brownmillerite variant in the orthorhombic space group Pcmb (No. 57) with unit cell parameters a=5.28960(10) Å, b=14.9240(2) Å, and c=10.9547(2) Å. Furthermore, with decreasing temperature, it undergoes re-entrant sequence of first-order structural phase transitions (Pcmb→ P2/c11→ P121/m1→ Pcmb) that is unprecedented among brownmillerites, broadening the family of space groups available to these materials and challenging current approaches for sortingmore » the myriad variants of brownmillerite structures. Magnetic susceptibility data indicate antiferromagnetic ordering in Ca 2Co 2O 5 occurs near 240 K, corroborated by neutron powder diffraction. Below 140 K, Ca 2Co 2O 5 shows a weak ferromagnetic component directed primarily along the b axis, and it also exhibits thermal and magnetic history dependence in magnetization.« less

Antiferromagnetic defect structure in LaNi O3 -δ single crystals

NASA Astrophysics Data System (ADS)

Wang, Bi-Xia; Rosenkranz, S.; Rui, X.; Zhang, Junjie; Ye, F.; Zheng, H.; Klie, R. F.; Mitchell, J. F.; Phelan, D.

2018-06-01

The origins of the metal-insulator and magnetic transitions exhibited by perovskite rare-earth nickelates, RNiO3 (where R is a rare-earth element), remain open issues, with charge disproportionation, magnetic interactions, and lattice response across multiple length scales being among the many possible origins. Recently, growth of single crystals of LaNiO3, which is the only member of these compounds that remains metallic in its ground state, has been reported, opening a new chapter in the investigation of the perovskite nickelates. Here, using a combination of magnetometry, heat capacity, and neutron scattering on as-grown and purposely reduced LaNi O3 -δ crystals, we show that both antiferromagnetic and ferromagnetic phases with a Néel temperature of ˜152 K and a Curie temperature of ˜225 K can be induced by reduction of the oxygen content. Transmission electron microscopy shows that these phases are characterized by ordered oxygen vacancy defect structures that exist as dilute secondary phases in as-grown crystals despite growth in partial oxygen pressures up to at least 130 bar. The demonstration of antiferromagnetism resulting from oxygen vacancy ordered structures implies that stoichiometry must be explicitly considered when interpreting the bulk properties of LaNi O3 -δ single crystals; accordingly, the implications of our results for putative oxygen-stoichiometric LaNiO3 are discussed.

Anomalous red luminescence of Sm3+ ions in Sm3+:LaKNaTaO5 single crystals

NASA Astrophysics Data System (ADS)

Korzeniowski, Kamil; Sobczyk, Marcin

2018-05-01

For the first time much more intense 4G5/2 → 6H9/2 transition than others 4G5/2→6HJ/2 transitions of the Sm3+-doped oxides have been observed. The Sm3+-doped LaKNaTaO5 single crystals have been grown by the flux growth method. The emission and excitation spectra as well as decay profiles of the 4G5/2 luminescent level of the Sm3+ ion have been measured. The decay curve has been fitted by the Inokuti-Hirayama energy transfer model which revealed that electric dipole-dipole interaction is responsible for the energy transfer processes in the Sm3+:LaKNaTaO5 single crystals. The title phosphors may be potentially used as red phosphor for white light-emitting diodes.

Hydrothermal Synthesis, Crystal Structure, and Photoluminescent Properties of Li[UO2(CH3COO)3]3[Co(H2O)6

NASA Astrophysics Data System (ADS)

AlDamen, Murad A.; Juwhari, Hassan K.; Al-zuheiri, Aya M.; Alnazer, Louy A.

2017-12-01

Single crystal of Li[UO2(CH3COO)3]3[Co(H2O)6] was prepared and found to crystallize in the monoclinic crystal system in the sp. gr. C2/ c, with Z = 2, and unit cell parameters a = 22.1857(15) Å, b = 13.6477(8) Å, c = 15.6921(10) Å, β = 117.842(9)°, V = 4201.3(4) Å3. The crystal was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The single crystal X-ray diffraction analysis revealed that the crystal has a lamellar structure in which a cobalt hydrate is sandwiched within the Li[UO2(CH3COO)3]3 2- chains. Furthermore, the room temperature photoluminescence spectrum of the complex was investigated in the solid state.

Properties of Lu3Al5O12, Lu3Al5O12:Pr, Lu3Al5O12:Pr,Mo, and (Lu1-x Y x )3Al5O12:Pr scintillator crystals

NASA Astrophysics Data System (ADS)

Talik, E.; Kusz, J.; Guzik, A.; Szubka, M.; Balin, K.; Kisielewski, J.; Wierzchowski, W.; Malinowska, A.; Strojny-Nedza, A.; Pajaczkowska, A.; Drozdowski, W.

2017-05-01

Lattice parameters, magnetic susceptibility, electronic structure, distribution of the elements and thermal properties were examined for single crystals of Lu3Al5O12 (LuAG) and (Lu1-x Y x )3Al5O12 (LuYAG) (x  =  0.25, 0.50, 0.75), either pure or doped with Pr and optionally co-doped with Mo, which are predicted as potential fast and efficient scintillators. It was indicated that specific cage-like surrounding of rare earth and aluminum ions built from oxygen ions and proper doping can influence the thermal conductivity and the emission process. Maximum light emission (LY) was observed at praseodymium concentration about 0.3 at.%. The growth atmosphere (Ar or N2) influences the crystal quality. Additional molybdenum doping below 0.01 at% concentration increases LY.

Temperature-dependent index of refraction of monoclinic Ga2O3 single crystal.

PubMed

Bhaumik, Indranil; Bhatt, R; Ganesamoorthy, S; Saxena, A; Karnal, A K; Gupta, P K; Sinha, A K; Deb, S K

2011-11-01

We present temperature-dependent refractive index along crystallographic b[010] and a direction perpendicular to (100)-plane for monoclinic phase (β) Ga(2)O(3) single crystal grown by the optical floating zone technique. The experimental results are consistent with the theoretical result of Litimein et al.1. Also, the Sellmeier equation for wavelengths in the range of 0.4-1.55 μm is formulated at different temperatures in the range of 30-175 °C. The thermal coefficient of refractive index in the above specified range is ~10(-5)/°C. © 2011 Optical Society of America

Crystallization kinetics of BaO-Al2O3-SiO2 glasses

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Hyatt, Mark J.

1989-01-01

Barium aluminosilicate glasses are being investigated as matrix materials in high-temperature ceramic composites for structural applications. Kinetics of crystallization of two refractory glass compositions in the barium aluminosilicate system were studied by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). From variable heating rate DTA, the crystallization activation energies for glass compositions (wt percent) 10BaO-38Al2O3-51SiO2-1MoO3 (glass A) and 39BaO-25Al2O3-35SiO2-1MoO3 (glass B) were determined to be 553 and 558 kJ/mol, respectively. On thermal treatment, the crystalline phases in glasses A and B were identified as mullite (3Al2O3-2SiO2) and hexacelsian (BaO-Al2O3-2SiO2), respectively. Hexacelsian is a high-temperature polymorph which is metastable below 1590 C. It undergoes structural transformation into the orthorhombic form at approximately 300 C accompanied by a large volume change which is undesirable for structural applications. A process needs to be developed where stable monoclinic celsian, rather than hexacelsian, precipitates out as the crystal phase in glass B.

Crystallization kinetics of BaO-Al2O3-SiO2 glasses

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Hyatt, Mark J.

1988-01-01

Barium aluminosilicate glasses are being investigated as matrix materials in high-temperature ceramic composites for structural applications. Kinetics of crystallization of two refractory glass compositions in the barium aluminosilicate system were studied by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). From variable heating rate DTA, the crystallization activation energies for glass compositions (wt percent) 10BaO-38Al2O3-51SiO2-1MoO3 (glass A) and 39BaO-25Al2O3-35SiO2-1MoO3 (glass B) were determined to be 553 and 558 kJ/mol, respectively. On thermal treatment, the crystalline phases in glasses A and B were identified as mullite (3Al2O3-2SiO2) and hexacelsian (BaO-Al2O3-2SiO2), respectively. Hexacelsian is a high-temperature polymorph which is metastable below 1590 C. It undergoes structural transformation into the orthorhombic form at approximately 300 C accompanied by a large volume change which is undesirable for structural applications. A process needs to be developed where stable monoclinic celsian, rather than hexacelsian, precipitates out as the crystal phase in glass B.

Growth of Nd doped (Lu, Gd)3(Ga, Al)5O12 single crystal by the micro pulling down method and their scintillation properties

NASA Astrophysics Data System (ADS)

Kamada, Kei; Kurosawa, Shunsuke; Yamaji, Akihiro; Shoji, Yasuhiro; Pejchal, Jan; Ohashi, Yuji; Yokota, Yuui; Yoshikawa, Akira

2015-03-01

Nd 1 mol% doped (Lu, Gd)3(Ga, Al)5O12 (LGGAG) single crystals were grown by the micro-pulling down (μ-PD) method. Luminescence and scintillation properties such as absorption, excitation and emission spectra, light yield and decay time were evaluated. Nd1%:Lu3Al5O12 showed the highest light output of around 8200 photons/MeV among the grown crystals. Scintillation decay time of Nd:Y3Al5O12 was 1.32 μs (36%) 2.02 μs (64%). Nd:Lu3Ga3Al2O12 was relatively high dense scintillator of 7.38 g/cm3 with good light yield of 6800 photons/MeV and scintillation decay time of 0.20 μs (5%) 2.60 μs (95%).

HOPPING CONDUCTIVITY AND MAGNETIC TRANSITIONS OF THE Cu2+ SPINS IN SINGLE-CRYSTAL La2CuO4+y

NASA Astrophysics Data System (ADS)

Thio, Tineke; Birgeneau, R. J.; Chen, C. Y.; Freer, B. S.; Gabbe, D. R.; Jenssen, H. P.; Kastner, M. A.; Picone, P. J.; Preyer, N. W.

Measurements are reported of the magnetoresistance (MR) for fields up to 23T in La2CuO4+y single crystals in which the Cu2+ spins order antiferromagnetically at TN˜240K, and in which the conductivity at low temperature is characterised by hopping between localised states. Using the MR, we map out the phase diagram of the spin flop transition, observed when the magnetic field is applied parallel to the zero-field staggered magnetisation, and that of the weak-ferromagnetic transition, observed with the field perpendicular to the CuO planes. In both transitions the antiferromagnetic propagation vector changes from the ěca direction at zero field to the ěcc direction at the highest fields. This rather subtle change of the Cu spin ordering is accompanied by a large increase in the interlayer hopping conductivity: up to a factor 2. We show that the magnetoconductance is proportional to the three-dimensional staggered moment with propagation vector in the orthorhombic ěcc direction. The origin of this unusual behaviour is an important unsolved problem.

Giant anisotropy of magnetocaloric effect in TbMnO3 single crystals

NASA Astrophysics Data System (ADS)

Jin, Jin-Ling; Zhang, Xiang-Qun; Li, Guo-Ke; Cheng, Zhao-Hua; Zheng, Lin; Lu, Yi

2011-05-01

The magnetocaloric effect (MCE) in TbMnO3 single crystals was investigated by isothermal magnetization curves for the ab plane at low temperatures. Large magnetic entropy change, ΔSM = -18.0 J/kg K, and the refrigerant capacity, RC = 390.7 J/kg, are achieved near the ordering temperature of Tb3+ moment (TNTb) under 70 kOe along the a axis. Furthermore, the TbMnO3 single crystal exhibits a giant MCE anisotropy. The difference of ΔSMand RC between the a and b axes is field and temperature dependent, which reaches maximum values of 11.4 J/kg K and 304.1 J/kg, respectively. By taking magnetocrystalline anisotropy into account, the rotating ΔSMwithin the ab plane can be well simulated, indicating that the anisotropy of ΔSMis directly contributed from the magnetocrystalline anisotropy. Our finding for giant MCE anisotropy in TbMnO3 single crystals explores the possibility of using this material for magnetic refrigerators by rotating its magnetization vector rather than moving it in and out of the magnet.

Thermal conductivity of Er{sup +3}:Y{sub 2}O{sub 3} films grown by atomic layer deposition

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

Raeisi Fard, Hafez; Hess, Andrew; Pashayi, Kamyar

2013-11-04

Cross-plane thermal conductivity of 800, 458, and 110 nm erbium-doped crystalline yttria (Er{sup +3}:Y{sub 2}O{sub 3}) films deposited via atomic layer deposition was measured using the 3ω method at room temperature. Thermal conductivity results show 16-fold increase in thermal conductivity from 0.49 W m{sup −1}K{sup −1} to 8 W m{sup −1}K{sup −1} upon post deposition annealing, partially due to the suppression of the number of the -OH/H{sub 2}O bonds in the films after annealing. Thermal conductivity of the annealed film was ∼70% lower than undoped bulk single crystal yttria. The cumulative interface thermal resistivity of substrate-Er{sup +3}:Y{sub 2}O{sub 3}-metal heater was determined tomore » be ∼2.5 × 10{sup −8} m{sup 2} K/W.« less

Rich structural chemistry in new alkali metal yttrium tellurites: three-dimensional frameworks of NaYTe4O10, KY(TeO3)2, RbY(TeO3)2, and a novel variant of hexagonal tungsten bronze, CsYTe3O8.

PubMed

Kim, Youngkwon; Lee, Dong Woo; Ok, Kang Min

2015-01-05

Pure polycrystalline phases and single crystals of four new quaternary alkali metal yttrium tellurites, NaYTe4O10, KY(TeO3)2, RbY(TeO3)2, and CsYTe3O8, have been prepared by solid-state and hydrothermal reactions using A2CO3 (A = Na, K, Rb, and Cs), Y(NO3)3·6H2O, Y2O3, and TeO2 as starting reagents. X-ray diffraction analyses suggest that NaYTe4O10 exhibits a highly symmetric three-dimensional (3D) framework consisting of YO8 square antiprisms and chains of TeO4 polyhedra. Within the framework, six- (6-) and eight-membered ring (8-MR) channels are observed. KY(TeO3)2 and RbY(TeO3)2 are isostructural to each other and reveal another 3D framework with structures containing YO6 octahedra and TeO3 trigonal pyramids with 4-MR and 12-MR channels. CsYTe3O8 shows a hexagonal tungsten bronze (HTB)-like topology composed of hexagonal tungsten oxide-like layers of TeO4 polyhedra and YO6 octahedral linkers with 3-MR and 6-MR channels. Thermal analyses, elemental analyses, and spectroscopic characterizations, such as UV-vis diffuse reflectance and infrared spectra, are presented, as are local dipole moment calculations for the constituent asymmetric polyhedra TeO3 and TeO4.

The photoluminescent properties of Y2O3:Bi3+, Eu3+, Dy3+ phosphors for white-light-emitting diodes.

PubMed

Han, Xiumei; Feng, Xu; Qi, Xiwei; Wang, Xiaoqiang; Li, Mingya

2014-05-01

Bi3+, Eu3+, Dy3+ activated Y2O3 phosphors were prepared through the sol-gel process. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, and photoluminescence (PL) spectra were used to characterize the resulting phosphors. The XRD patterns show the refined crystal structure of Y2O3. The energy transfer processes of Bi(3+)-Eu3+ occurred in the host lattices. The thermal stability of Y2O3:Bi3+, Eu3+, Dy3+ phosphors was studied. Under short wavelength UV excitation, the phosphors show excellent characteristic red, blue, and yellow emission with medium intensity.

Sonochemical synthesis of highly luminescent Ln 2O 3:Eu 3+ (Y, La, Gd) nanocrystals

DOE PAGES

Alammar, Tarek; Cybinska, Joanna; Campbell, Paul S.; ...

2015-05-12

In this study, sonication of Ln(CH 3COO) 3·H 2O, Eu(CH 3COO) 3·H 2O and NaOH dissolved in the ionic liquid-butyl-3-methylimidazolium bis(trifluoromethane)sulfonylamide lead to Ln(OH) 3:Eu (Ln: Gd, La, Y) nanoparticles. Subsequent calcination at 800 °C for 3 h allowed to obtain Ln 2O 3:Eu nanopowders. Gd 2O 3 and Y 2O 3 were obtained in the C-type lanthanide sequioxide structure, whereas La 2O 3 crystallized in the A-type. Structure, morphology, and luminescent properties of the nano-oxides were investigated by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), dispersive X-ray (EDX), and photoluminescence (PL). SEM studies revealed that the synthesized Gdmore » 2O 3:Eu, La 2O 3:Eu, and Y 2O 3:Eu formed nano-spindle, -sheets, and -rods in shape, respectively. The nanoscale materials show very efficient red emission due to the intraconfigurational f–f transitions of Eu 3+. The quantum yields for Ln 2O 3:Eu (5%) were determined to be 4.2% for Ln=Gd, 13.8% for Ln=Y and 5.2% for Ln=La. The asymmetric ratio I 02/I 01 of Eu 3+ varies from 5.3 for Gd 2O 3, to 5.6 for Y 2O 3 to 6.5 for La 2O 3, which increased the color chromaticity.« less

Crystal growth and electrical properties of CuFeO 2 single crystals

NASA Astrophysics Data System (ADS)

Dordor, P.; Chaminade, J. P.; Wichainchai, A.; Marquestaut, E.; Doumerc, J. P.; Pouchard, M.; Hagenmuller, P.; Ammar, A.

1988-07-01

Delafossite-type CuFeO 2 single crystals have been prepared by a flux method: crystals obtained in a Cu crucible with LiBO 2 as flux are n-type whereas those prepared in a Pt crucible with a Cu 2O flux are p-type. Electrical measurements have revealed that n-type crystals exhibit weak anisotropic conductivities with large activation energies and small mobilities (r.t. values perpendicular and parallel to the c-axis: μ⊥ = 5 × 10 -5 and μ‖ = 10 -7 cm -2 V -1 sec -1). p-type crystals, less anisotropic, are characterized by low activation energies and higher mobilities ( μ⊥ = 34 and μ‖ = 8.9 cm 2 V -1 sec -1). A two -conduction-band model is proposed to account for the difference observed between the energy gap value deduced from photoelectrochemical measurements and the activation energy of the electrical conductivity in the intrinsic domain.

Single-crystalline oxide films of the Al2O3-Y2O3-R2O3 system as optical sensors of various types of ionizing radiation: significant advantages over volume analogs

NASA Astrophysics Data System (ADS)

Zorenko, Yuri V.; Batenchuk, M.; Gorbenco, V.; Pashkovsky, M.

1997-02-01

This investigation is dedicated to studying of peculiarities of luminescent properties of the single crystalline films (SCF) of Al2O3-Y2O3-R2O3 oxide system with alpha-Al2O3 and garnet structure, which are used as various types of ionizing radiation luminescent detectors. These peculiarities define the number of nontrivial advantages over their volume analogues. It is shown that SCF are characterized by the low concentrations of vacancy type defects and substituent defects, and the high concentration of Pb ion as dopant. This allows us to substantially increase the spatial resolution and selectivity of cathodoluminophores on the base of these compounds.

Radiation damage induced in Al2O3 single crystal by 90 MeV Xe ions

NASA Astrophysics Data System (ADS)

Zirour, H.; Izerrouken, M.; Sari, A.

2015-12-01

Radiation damage induced in Al2O3 single crystal by 90 MeV Xe ions were investigated by optical absorption measurements, Raman spectroscopy and X-ray diffraction (XRD) techniques. The irradiations were performed at the GANIL accelerator in Caen, France for the fluence in the range from 1012 to 6 × 1013 cm-2 at room temperature under normal incidence. The F+ and F22+ centers kinetic as a function of fluence deduced from the optical measurements explains that the single defects (F and F+) aggregate to F center clusters (F2 , F2+, F22+) during irradiation at high fluence (>1013 cm-2). Raman and XRD analysis reveal a partial disorder of 40% of Al2O3 in the studied fluence range in accordance with Kabir et al. (2008) study. The result suggests that this is due to the stress relaxation process which occurs at high fluence (>1013 cm-2).

Luminescent properties of Cr-doped (GdX, Y1-X)3Al5O12 infra-red scintillator crystals

NASA Astrophysics Data System (ADS)

Suzuki, Akira; Kurosawa, Shunsuke; Yamaji, Akihiro; Shoji, Yasuhiro; Pejchal, Jan; Kamada, Kei; Yokota, Yuui; Yoshikawa, Akira

2014-10-01

Cr-doped (GdX Y1-X)3Al5O12 (X = 0, 0.25, 0.50) crystals prepared by the micro-pulling down method were investigated to develop a infra-red scintillator for implantable patient dosimeter in radiation therapy. In order to evaluate their optical and scintillation performance, the following properties were measured: (i) transmittance between ultra-violet and near-infra red region, (ii) photoluminescence spectra under Xe-lamp excitation, and (iii) X-ray excited radio-luminescence spectra. Cr:Y3Al5O12 and Cr:(Gd0.25 Y0.75)3Al5O12 crystals showed increased transmittance of 80%, while Cr:(Gd0.50 Y0.50)3Al5O12 had a lower transmittance of 40% due to its polycrystalline structure. In addition, all the Cr:(GdX Y1-X)3Al5O12 crystals showed sharp scintillation luminescence peaks ascribed to Cr3+ d-d transitions. Therefore, these results suggested that Cr:Y3Al5O12 and Cr:(Gd0.25 Y0.75)3Al5O12 crystals can be candidate materials for the dosimeter use.

Synthesis, crystal structure and magnetic properties of superconducting single crystals of HgBa2CuO4+δ

NASA Astrophysics Data System (ADS)

Bertinotti, A.; Viallet, V.; Colson, D.; Marucco, J.-F.; Hammann, J.; Forget, A.; Le Bras, G.

1996-02-01

Single crystals of HgBa2CuO4+δ of submillimetric sizes were grown with the same one step, low pressure, gold amalgamation technique used to obtain single crystals of HgBa2Ca2Cu3O8+δ. Remarkable superconducting properties are displayed by the samples which are optimally doped as grown. The sharpness of the transition profiles of the magnetic susceptibility, its anisotropy dependence and the volume fraction exhibiting the Meissner effect exceed the values obtained with the best crystal samples of Hg-1223. X-rays show that no substitutional defects have been found in the mercury plane, in particular no mixed occupancy of copper at the mercury site. The interstitial oxygen content at (1/2, 1/2, 0) δ = 0.066+/-0.008 is about one third that observed in optimally doped Hg-1223, resulting in an identical doping level per CuO2 plane in both compounds.

Raman scattering spectra of superconducting Bi2Sr2CaCu2O8 single crystals

NASA Astrophysics Data System (ADS)

Kirillov, D.; Bozovic, I.; Geballe, T. H.; Kapitulnik, A.; Mitzi, D. B.

1988-12-01

Raman spectra of Bi2Sr2CaCu2O8 single crystals with superconducting phase-transition temperature of 90 K have been studied. The spectra contained phonon lines and electronic continuum. Phonon energies and polarization selection rules were measured. A gap in the electronic continuum spectrum was observed in a superconducting state. Noticeable similarity between Raman spectra of Bi2Sr2CaCu2O8 and YBa2Cu3O7 was found.

Floating zone growth of α-Na 0.90MnO 2 single crystals

DOE PAGES

Dally, Rebecca; Clement, Raphaele J.; Chisnell, Robin; ...

2016-12-03

Here, single crystal growth of α-Na xMnO 2 (x=0.90) is reported via the floating zone technique. The conditions required for stable growth and intergrowth-free crystals are described along with the results of trials under alternate growth atmospheres. Chemical and structural characterizations of the resulting α-Na 0.90MnO 2 crystals are performed using ICP-AES NMR, XANES, XPS, and neutron diffraction measurements. As a layered transition metal oxide with large ionic mobility and strong correlation effects, α-Na xMnO 2 is of interest to many communities, and the implications of large volume, high purity, single crystal growth are discussed.

Growth and properties of oxygen- and ion-doped Bi2Sr2CaCu2O8+δ single crystals

NASA Astrophysics Data System (ADS)

Mitzi, D. B.; Lombardo, L. W.; Kapitulnik, A.; Laderman, S. S.; Jacowitz, R. D.

1990-04-01

A directional solidification method for growing large single crystals in the Bi2Sr2CaCu2O8+δ system is reported. Ion doping, with replacement of La for Sr and Y for Ca, as well as oxygen doping in these crystals has been explored. Doped and undoped crystals have been characterized using microprobe analysis, x-ray diffraction, thermogravimetric analysis, and magnetic and Hall measurements. Ion doping results in little change of the superconducting transition for substitution levels below 20-25%, while beyond this level the Meissner signal broadens and the low-temperature Meissner signal decreases. Microprobe analysis and x-ray diffraction performed on these more highly substituted single crystals provide evidence for inhomogeneity and phase segregation into regions of distinct composition. Annealing unsubstituted crystals in increasing partial pressures of oxygen reversibly depresses the superconducting transition temperature from 90 (as made) to 77 K (oxygen pressure annealed), while the carrier concentrations, as determined from Hall effect measurements, increase from n=3.1(3)×1021 cm-3 (0.34 holes per Cu site) to 4.6(3)×1021 cm-3 (0.50 holes per Cu site). No degradation of the Meissner transition or other indications of inhomogeneity or phase segregation with doping are noted, suggesting that oxygen-doped Bi2Sr2CaCu2O8+δ is a suitable system for pursuing doping studies. The decrease in Tc with concentration for 0.34<=n<=0.50 indicates that a high-carrier-concentration regime exists in which Tc decreases with n and suggests that this decrease does not arise from material inhomogeneity or other materials problems. An examination of the variation of Tc with the density of states and lattice constants for all of the doped and undoped superconducting samples considered here indicates that changes in Tc with doping are primarily affected by changes in the density of states (or carrier concentration) rather than by structural variation induced by the doping.

Preparation of fine single crystals of magnetic superconductor RuSr2GdCu2O8-δ by partial melting

NASA Astrophysics Data System (ADS)

Yamaki, Kazuhiro; Bamba, Yoshihiro; Irie, Akinobu

2018-03-01

In this study, fine uniform RuSr2GdCu2O8-δ (RuGd-1212) single crystals have been successfully prepared by partial melting. Synthesis temperature could be lowered to a value not exceeding the decomposition temperature of RuGd-1212 using the Sr-Gd-Cu-O flux. The crystals grown by alumina boats are cubic, which coincides with the result of a previous study of RuGd-1212 single crystals using platinum crucibles. The single crystals were up to 15 × 15 × 15 µm3 in size and their lattice constants were consistent with those of polycrystalline samples reported previously. Although the present size of single crystals is not sufficient for measurements, the partial melting technique will be beneficial for future progress of research using RuGd-1212 single crystals. Appropriate nominal composition, sintering atmosphere, and temperature are essential factors for growing RuGd-1212 single crystals.

Effects of SiO 2 overlayer at initial growth stage of epitaxial Y 2O 3 film growth

NASA Astrophysics Data System (ADS)

Cho, M.-H.; Ko, D.-H.; Choi, Y. G.; Lyo, I. W.; Jeong, K.; Whang, C. N.

2000-12-01

We investigated the dependence of the Y 2O 3 film growth on Si surface at initial growth stage. The reflection high-energy electron diffraction, X-ray scattering, and atomic force microscopy showed that the film crystallinity and morphology strongly depended on whether Si surface contained O or not. In particular, the films grown on oxidized surfaces revealed significant improvement in crystallinity and surface smoothness. A well-ordered atomic structure of Y 2O 3 film was formed on 1.5 nm thick SiO 2 layer with the surface and interfacial roughness markedly enhanced, compared with the film grown on the clean Si surfaces. The epitaxial film on the oxidized Si surface exhibited extremely small mosaic structures at interface, while the film on the clean Si surface displayed an island-like growth with large mosaic structures. The nucleation sites for Y 2O 3 were provided by the reaction between SiO 2 and Y at the initial growth stage. The SiO 2 layer known to hinder crystal growth is found to enhance the nucleation of Y 2O 3, and provides a stable buffer layer against the silicide formation. Thus, the formation of the initial SiO 2 layer is the key to the high-quality epitaxial growth of Y 2O 3 on Si.

Antiferromagnetic defect structure in LaNi O 3 – δ single crystals

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

Wang, Bi -Xia; Rosenkranz, Stephan; Rui, X.

Here, the origins of the metal-insulator and magnetic transitions exhibited by perovskite rare-earth nickelates, RNiO 3 (where R is a rare-earth element), remain open issues, with charge disproportionation, magnetic interactions, and lattice response across multiple length scales being among the many possible origins. Recently, growth of single crystals of LaNiO 3, which is the only member of these compounds that remains metallic in its ground state, has been reported, opening a new chapter in the investigation of the perovskite nickelates. Here, using a combination of magnetometry, heat capacity, and neutron scattering on as-grown and purposely reduced LaNiO 3–δ crystals, wemore » show that both antiferromagnetic and ferromagnetic phases with a Néel temperature of ~152 K and a Curie temperature of ~225 K can be induced by reduction of the oxygen content. Transmission electron microscopy shows that these phases are characterized by ordered oxygen vacancy defect structures that exist as dilute secondary phases in as-grown crystals despite growth in partial oxygen pressures up to at least 130 bar. The demonstration of antiferromagnetism resulting from oxygen vacancy ordered structures implies that stoichiometry must be explicitly considered when interpreting the bulk properties of LaNiO 3–δ single crystals; accordingly, the implications of our results for putative oxygen-stoichiometric LaNiO 3 are discussed.« less

Antiferromagnetic defect structure in LaNi O 3 – δ single crystals

DOE PAGES

Wang, Bi -Xia; Rosenkranz, Stephan; Rui, X.; ...

2018-06-12

Here, the origins of the metal-insulator and magnetic transitions exhibited by perovskite rare-earth nickelates, RNiO 3 (where R is a rare-earth element), remain open issues, with charge disproportionation, magnetic interactions, and lattice response across multiple length scales being among the many possible origins. Recently, growth of single crystals of LaNiO 3, which is the only member of these compounds that remains metallic in its ground state, has been reported, opening a new chapter in the investigation of the perovskite nickelates. Here, using a combination of magnetometry, heat capacity, and neutron scattering on as-grown and purposely reduced LaNiO 3–δ crystals, wemore » show that both antiferromagnetic and ferromagnetic phases with a Néel temperature of ~152 K and a Curie temperature of ~225 K can be induced by reduction of the oxygen content. Transmission electron microscopy shows that these phases are characterized by ordered oxygen vacancy defect structures that exist as dilute secondary phases in as-grown crystals despite growth in partial oxygen pressures up to at least 130 bar. The demonstration of antiferromagnetism resulting from oxygen vacancy ordered structures implies that stoichiometry must be explicitly considered when interpreting the bulk properties of LaNiO 3–δ single crystals; accordingly, the implications of our results for putative oxygen-stoichiometric LaNiO 3 are discussed.« less

Schottky barrier diode based on β-Ga2O3 (100) single crystal substrate and its temperature-dependent electrical characteristics

NASA Astrophysics Data System (ADS)

He, Qiming; Mu, Wenxiang; Dong, Hang; Long, Shibing; Jia, Zhitai; Lv, Hangbing; Liu, Qi; Tang, Minghua; Tao, Xutang; Liu, Ming

2017-02-01

The Pt/β-Ga2O3 Schottky barrier diode and its temperature-dependent current-voltage characteristics were investigated for power device application. The edge-defined film-fed growth (EFG) technique was utilized to grow the (100)-oriented β-Ga2O3 single crystal substrate that shows good crystal quality characterized by X-ray diffraction and high resolution transmission electron microscope. Ohmic and Schottky electrodes were fabricated by depositing Ti and Pt metals on the two surfaces, respectively. Through the current-voltage (I-V) measurement under different temperature and the thermionic emission modeling, the fabricated Pt/β-Ga2O3 Schottky diode was found to show good performances at room temperature, including rectification ratio of 1010, ideality factor (n) of 1.1, Schottky barrier height (ΦB) of 1.39 eV, threshold voltage (Vbi) of 1.07 V, ON-resistance (RON) of 12.5 mΩ.cm2, forward current density at 2 V (J@2V) of 56 A/cm2, and saturation current density (J0) of 2 × 10-16 A/cm2. The effective donor concentration Nd - Na was calculated to be about 2.3 × 1014 cm3. Good temperature dependent performance was also found in the device. The Schottky barrier height was estimated to be about 1.3 eV-1.39 eV at temperatures ranging from room temperature to 150 °C. With increasing temperature, parameters such as RON and J@2V become better, proving that the diode can work well at high temperature. The EFG grown β-Ga2O3 single crystal is a promising material to be used in the power devices.

Positron annihilation on the surfaces of SiO 2 films thermally grown on single crystal of Cz-Si

NASA Astrophysics Data System (ADS)

Deng, Wen; Yue, Li; Zhang, Wei; Cheng, Xu-xin; Zhu, Yan-yan; Huang, Yu-yang

2009-09-01

Two-detector coincidence system and mono-energetic slow positron beam has been applied to measure the Doppler broadening spectra for single crystals of SiO2, SiO2 films with different thickness thermally grown on single crystal of Cz-Si, and single crystal of Si without oxide film. Oxygen is recognized as a peak at about 11.85 × 10-3m0c on the ratio curves. The S parameters decrease with the increase of positron implantation energy for the single crystal of SiO2 and Si without oxide film. However, for the thermally grown SiO2-Si sample, the S parameters in near surface of the sample increase with positron implantation energy. It is due to the formation of silicon oxide at the surface, which lead to lower S value. S and W parameters vary with positron implantation depth indicate that the SiO2-Si system consist of a surface layer, a SiO2 layer, a SiO2-Si interface layer and a semi-infinite Si substrate.

Raman Spectrum of Er-Y-codoped ZrO2 and Fluorescence Properties of Er3+

NASA Astrophysics Data System (ADS)

He, Jun; Luo, Meng-fei; Jin, Ling-yun; He, Mai; Fang, Ping; Xie, Yun-long

2007-02-01

Er-Y-codoped ZrO2 mixed oxides with monoclinic, tetragonal and cubic structures were prepared by a sol-gel method. The crystal structure of ZrO2 matrix and the effect of the ZrO2 phases on the fluorescence properties of Er3+ were studied using Raman spectroscopy. The results indicated that the fluorescence properties of Er3+ depend on its local ZrO2 crystal structures. As ZrO2 matrix transferred from monoclinic to tetragonal and cubic phase, the Raman and fluorescence bands of Er3+ decreased in intensities and tended to form a single peak. With 632.8 nm excitation, the bands between 640 and 680 nm were attributed to the fluorescence of Er3+ in the ZrO2 environment. However, only the fluorescence was observed and no Raman spectra were seen under 514.5 nm excitation, while only Raman spectra were observed under 325 nm excitation. UV Raman spectroscopy was found to be more sensitive in the surface region while the information provided by XRD mainly came from the bulk. The phase with lower symmetry forms more easily on the surface than in the bulk.

Molecular dynamics simulation of fast particle irradiation on the single crystal CeO2

NASA Astrophysics Data System (ADS)

Sasajima, Y.; Ajima, N.; Osada, T.; Ishikawa, N.; Iwase, A.

2013-11-01

We used a molecular dynamics method to simulate structural relaxation caused by the high-energy-ion irradiation of single crystal CeO2. As the initial condition, we assumed high thermal energy was supplied to the individual atoms within a cylindrical region of nanometer-order diameter located in the center of the single crystal. The potential proposed by Inaba et al. was utilized to calculate interactions between atoms [H. Inaba, R. Sagawa, H. Hayashi, K. Kawamura, Solid State Ionics 122 (1999) 95-103]. The supplied thermal energy was first spent to change the crystal structure into an amorphous one within a short period of about 0.3 ps, then it was dissipated in the crystal. We compared the obtained results with those of computer simulations for UO2 and found that CeO2 was more stable than UO2 when supplied with high thermal energy.

Growth and spectroscopic properties of Tm3+:NaBi(MoO4)2 single crystal

NASA Astrophysics Data System (ADS)

Gusakova, N. V.; Mudryi, A. V.; Demesh, M. P.; Yasukevich, A. S.; Pavlyuk, A. A.; Kornienko, A. A.; Dunina, E. B.; Khodasevich, I. A.; Orlovich, V. A.; Kuleshov, N. V.

2018-06-01

In this work we report the spectroscopic properties of Tm3+:NaBi(MoO4)2 crystals with the dopant concentrations of 0.7 at.% and 3 at.%. The energy levels of the Tm3+ in the NaBi(MoO4)2 host were determined from polarized optical absorption and photoluminescence spectra measured at 77.4 K. Radiative properties of the crystals were calculated in context of Judd-Ofelt theory. Raman spectra of the crystal were studied. The concentration dependences of emission decay times of 3H4 and 3F4 levels were analyzed. The potential of the crystal for building tunable and ultrafast pulse lasers is shown on the base of cross sections and gain coefficient in the range of 1.9 μm.

Highly polarized single-c-domain single-crystal Pb(Mn,Nb)O(3)-PZT thin films.

PubMed

Wasa, Kiyotaka; Adachi, Hideaki; Nishida, Ken; Yamamoto, Takashi; Matsushima, Tomoaki; Kanno, Isaku; Kotera, Hidetoshi

2012-01-01

In-plane unstrained single-c-domain/single-crystal thin films of PZT-based ternary ferroelectric perovskite, ξPb(Mn,Nb)O3-(1 - ξ)PZT, were grown on SrRuO(3)/Pt/MgO substrates using magnetron sputtering followed by quenching. The sputtered unstrained thin films exhibit unique ferroelectric properties: high coercive field, Ec > 180 kV/cm, large remanent polarization, P(r) = 100 μC/cm(2), small relative dielectric constants, ε* = 100 to 150, high Curie temperature, Tc = ~600 °C, and bulk-like large transverse piezoelectric constants, e31,f = -12.0 C/m(2) for PZT(48/52) at ξ = 0.06. The unstrained thin films are an ideal structure to extract the bulk ferroelectric properties. Their micro-structures and ferroelectric properties are discussed in relation to the potential applications for piezoelectric MEMS. © 2012 IEEE

Comparative study of flux pinning, creep and critical currents between YBaCuO crystals with and without Y2BaCuO5 inclusions

NASA Technical Reports Server (NTRS)

Murakami, Masato; Gotoh, Satoshi; Fujimoto, Hiroyuki; Koshizuka, Naoki; Tanaka, Shoji

1991-01-01

In the Y-Ba-Cu-O system, YBa2Cu3O(x) phase is produced by the following peritectic reaction: Y2BaCuO5 + liquid yields 2YBa2Cu3O(x). Through the control of processing conditions and starting compositions, it becomes possible to fabricate large crystals containing fine Y2BaCuO5(211) inclusions. Such crystals exhibit Jc values exceeding 10000 A/sq cm at 77 K and 1T. Recently, researchers developed a novel process which can control the volume fraction of 211 inclusions. Elimination of 211 inclusions is also possible. In this study, researchers prepared YBaCuO crystals with and without 211 inclusions using the novel process, and compared flux pinning, flux creep and critical currents. Magnetic field dependence of Jc for YBaCuO crystals with and with 211 inclusions is shown. It is clear that fine 211 inclusions can contribute to flux pinning. It was also found that flux creep rate could be reduced by increasing flux pinning force. Critical current density estimates based on the conventional flux pinning theory were in good agreement with experimental results.

Fabrication of SiO2@ZrO2@Y2O3:Eu3+ core-multi-shell structured phosphor.

PubMed

Gao, Xuan; He, Diping; Jiao, Huan; Chen, Juan; Meng, Xin

2011-08-01

ZrO2 interface was designed to block the reaction between SiO2 and Y2O3 in SiO2@Y2O3:Eu coreshell structure phosphor. SiO2@ZrO2@Y2O3:Eu core-multi-shell phosphors were successfully synthesized by combing an LBL method with a Sol-gel process. Based on electron microscopy, X-ray diffraction, and spectroscopy experiments, compelling evidence for the formation of the Y2O3:Eu outer shell on ZrO2 were presented. The presence of ZrO2 layer on SiO2 core can block the reaction of SiO2 core and Y2O3 shell effectively. By this kind of structure, the reaction temperature of the SiO2 core and Y2O3 shell in the SiO2@Y2O3:Eu core-shell structure phosphor can be increased about 200-300 degrees C and the luminescent intensity of this structure phosphor can be improved obviously. Under the excitation of ultraviolet (254 nm), the Eu3+ ion mainly shows its characteristic red (611 nm, 5D0-7F2) emissions in the core-multi-shell particles from Y2O3:Eu3+ shells. The emission intensity of Eu3+ ions can be tuned by the annealing temperatures, the number of coating times, and the thickness of ZrO2 interface, respectively.

Structural properties of Y2O3–Al2O3 liquids and glasses: An overview

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

Wilding, Martin C.; Wilson, Mark; McMillan, Paul F.

2015-01-01

Liquids in the system Y2O3- Al2O3 have been the subject of considerable study because of the reported occurrence of a first-order density and entropy-driven liquid-liquid phase transition (LLPT) in the supercooled liquid state. The observations have become controversial because of the presence of crystalline material that can be formed simultaneously and that can mask the nucleation and growth of the lower density liquid. The previous work is summarized here along with arguments for and against the different viewpoints. Also two studies have been undertaken to investigate the LLPT in this refractory system with emphasis on determining the structure of unequivocallymore » amorphous materials. These include the in situ high energy X-ray diffraction (HEXRD) of supercooled Y2O3 - Al2O3 liquids and the low frequency vibrational dynamics of recovered glasses. Manybody molecular dynamics simulations are also used to interpret the results of both studies. The HEXRD measurements, combined with aerodynamic levitation and rapid data acquisition techniques, show that for the 20 mol% Y2O3 (i.e. AlY20) liquid there is a shift in the position of the first peak in the diffraction pattern over a narrow temperature range (2100-1800 K) prior to crystallization. Microbeam Raman spectroscopy measurements made on AlY20 glasses clearly show contrasting spectra in the low frequency part of the spectrum for low(LDA) and high-density (HDA) glassy regions. The molecular dynamics simulations identify contrasting coordination environments around oxygen anions for the high- (HDL) and low-density (LDL) liquids. (C) 2014 Elsevier B.V. All rights reserved.« less

Structural properties of Y 2O 3–Al 2O 3 liquids and glasses: An overview

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

Wilding, Martin C.; Wilson, Mark; McMillan, Paul F.

2015-01-01

Liquids in the system Y 2O 3–Al 2O 3 have been the subject of considerable study because of the reported occurrence of a first-order density and entropy-driven liquid-liquid phase transition (LLPT) in the supercooled liquid state. The observations have become controversial because of the presence of crystalline material that can be formed simultaneously and that can mask the nucleation and growth of the lower density liquid. The previous work is summarized here along with arguments for and against the different viewpoints. Also two studies have been undertaken to investigate the LLPT in this refractory system with emphasis on determining themore » structure of unequivocally amorphous materials. These include the in situ high energy X-ray diffraction (HEXRD) of supercooled Y 2O 3–Al 2O 3 liquids and the low frequency vibrational dynamics of recovered glasses. Manybody molecular dynamics simulations are also used to interpret the results of both studies. The HEXRD measurements, combined with aerodynamic levitation and rapid data acquisition techniques, show that for the 20 mol% Y 2O 3 (i.e. AlY20) liquid there is a shift in the position of the first peak in the diffraction pattern over a narrow temperature range (2100-1800 K) prior to crystallization. Microbeam Raman spectroscopy measurements made on AlY20 glasses clearly show contrasting spectra in the low frequency part of the spectrum for low(LDA) and high-density (HDA) glassy regions. The molecular dynamics simulations identify contrasting coordination environments around oxygen anions for the high- (HDL) and low-density (LDL) liquids. (C) 2014 Elsevier B.V. All rights reserved.« less

Effect of CeO2 and Y2O3 on microstructure, bioactivity and degradability of laser cladding CaO-SiO2 coating on titanium alloy.

PubMed

Li, H C; Wang, D G; Chen, C Z; Weng, F

2015-03-01

To solve the lack of strength of bulk biomaterials for load-bearing applications and improve the bioactivity of titanium alloy (Ti-6Al-4V), CaO-SiO2 coatings on titanium alloy were fabricated by laser cladding technique. The effect of CeO2 and Y2O3 on microstructure and properties of laser cladding coating was analyzed. The cross-section microstructure of ceramic layer from top to bottom gradually changes from cellular-dendrite structure to compact cellular crystal. The addition of CeO2 or Y2O3 refines the microstructure of the ceramic layer in the upper and middle regions. The refining effect on the grain is related to the kinds of additives and their content. The coating is mainly composed of CaTiO3, CaO, α-Ca2(SiO4), SiO2 and TiO2. Y2O3 inhibits the formation of CaO. After soaking in simulated body fluid (SBF), the calcium phosphate layer is formed on the coating surface, indicating the coating has bioactivity. After soaking in Tris-HCl solution, the samples doped with CeO2 or Y2O3 present a lower weight loss, indicating the addition of CeO2 or Y2O3 improves the degradability of laser cladding sample. Copyright © 2015 Elsevier B.V. All rights reserved.

Valence-band and core-level photoemission study of single-crystal Bi2CaSr2Cu2O8 superconductors

NASA Astrophysics Data System (ADS)

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

1988-12-01

High-quality single crystals of Bi2CaSr2Cu2O8 superconductors have been prepared and cleaved in ultrahigh vacuum. Low-energy electron diffraction measurements show that the surface structure is consistent with the bulk crystal structure. Ultraviolet photoemission and x-ray photoemission experiments were performed on these well-characterized sample surfaces. The valence-band and the core-level spectra obtained from the single-crystal surfaces are in agreement with spectra recorded from polycrystalline samples, justifying earlier results from polycrystalline samples. Cu satellites are observed both in the valence band and Cu 2p core level, signaling the strong correlation among the Cu 3d electrons. The O 1s core-level data exhibit a sharp, single peak at 529-eV binding energy without any clear satellite structures.

Synthesis of single-crystal perovskite PbCrO3 through a new reaction route at high pressure

NASA Astrophysics Data System (ADS)

Han, Yunxia; Wang, Shanmin; Liu, Yinjuan; Ma, Dejiang; He, Duanwei; Zhao, Yusheng

2018-04-01

As a new member in the family of Mott system, perovskite PbCrO3 has recently been uncovered to exhibit fantastic structural transition under pressure, coupled with magnetic, electronic, and ferromagnetic transitions, which provide many opportunities for understanding of correlated system. However, it is still challenging to synthesize high-quality single-crystal PbCrO3, leading to the limited exploration of this Mott compound. In this work, we formulate a new high-pressure reaction route for preparation of high-quality PbCrO3 crystals between PbCl2 and Na2CrO4 at high pressure of 5-10 GPa and at high temperature of 750-1500°C. Because of the formation of reaction byproduct NaCl, the final product can readily be separated by washing with water. The obtained sample is in the form of single crystal with crystallite size up to 200 μm. In addition, combined with X-ray diffraction measurement, a tentative pressure-temperature synthesis diagram of PbCrO3 is mapped out from the reaction between PbCl2 and Na2CrO4 and the reaction mechanism is also explored in detail.

Novel ZrO2 based ceramics stabilized by Fe2O3, SiO2 and Y2O3

NASA Astrophysics Data System (ADS)

Rada, S.; Culea, E.; Rada, M.

2018-03-01

Samples in the 5Fe2O3·10SiO2·xY2O3·(85-x)ZrO2 composition where x = 5, 10 and 15 mol% Y2O3 were synthesized and investigated by XRD, SEM, density measurements, FTIR, UV-Vis, EPR and PL spectroscopies. X-ray diffraction patterns confirm the presence of the tetragonal and cubic ZrO2 crystalline phases in all samples. The IR data show the overlaps of absorption bands assigned to Zrsbnd Osbnd Zr and Sisbnd Osbnd linkages in samples. UV-Vis and PL data indicate higher concentrations of intrinsic defects by doping with Y2O3 concentrations. The EPR spectra are characterized by two resonance lines situated at about g ∼ 4.3 and g ∼ 2 for lower Y2O3 contents.

Crystal field excitations from Yb3 + ions at defective sites in highly stuffed Yb2Ti2O7

NASA Astrophysics Data System (ADS)

Sala, G.; Maharaj, D. D.; Stone, M. B.; Dabkowska, H. A.; Gaulin, B. D.

2018-06-01

The pyrochlore magnet Yb2Ti2O7 has been proposed as a quantum spin ice candidate, a spin liquid state expected to display emergent quantum electrodynamics with gauge photons among its elementary excitations. However, Yb2Ti2O7 's ground state is known to be very sensitive to its precise stoichiometry. Powder samples, produced by solid-state synthesis at relatively low temperatures, tend to be stoichiometric, while single crystals grown from the melt tend to display weak "stuffing" wherein ˜2 % of the Yb3 +, normally at the A site of the A2B2O7 pyrochlore structure, reside as well at the B site. In such samples Yb3 + ions should exist in defective environments at low levels and be subjected to crystalline electric fields very different from those at the stoichiometric A sites. Neutron scattering measurements of Yb3 + in four compositions of Yb2 +xTi2 -xO7 -y show the spectroscopic signatures for these defective Yb3 + ions and explicitly demonstrate that the spin anisotropy of the Yb3 + moment changes from X Y -like for stoichiometric Yb3 + to Ising-like for "stuffed" B site Yb3 + or for A site Yb3 + in the presence of oxygen vacancies.

Defect types and room-temperature ferromagnetism in undoped rutile TiO2 single crystals

NASA Astrophysics Data System (ADS)

Li, Dong-Xiang; Qin, Xiu-Bo; Zheng, Li-Rong; Li, Yu-Xiao; Cao, Xing-Zhong; Li, Zhuo-Xin; Yang, Jing; Wang, Bao-Yi

2013-03-01

Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane. By combining X-ray absorption near the edge structure spectrum and positron annihilation lifetime spectroscopy, Ti3+—VO defect complexes (or clusters) have been identified in annealed crystals at a high vacuum. We elucidate that the unpaired 3d electrons in Ti3+ ions provide the observed room-temperature ferromagnetism. In addition, excess oxygen ions in the TiO2 lattice could induce a number of Ti vacancies which obviously increase magnetic moments.

Hydrothermal synthesis of Y{sub 2}O{sub 3} coated Y{sub 2}O{sub 3}:Eu{sup 3+} nanotubes for enhanced photoluminescence properties

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

Gao, Linhui, E-mail: gaolhui@zstu.edu.cn; Wang, Guangfa; Zhu, Hongliang

Highlights: • Eu{sup 3+} doped Y{sub 2}O{sub 3} nanotubes. • Hydrothermal synthesis of Y{sub 2}O{sub 3} coated Y{sub 2}O{sub 3}:Eu{sup 3+} nanostructures assissted with a further heat treatment. • Tunable coating ratios of Y{sub 2}O{sub 3} coated Y{sub 2}O{sub 3}:Eu{sup 3+} nanophosphor. • Enhanced photoluminescence intensity of Y{sub 2}O{sub 3}:Eu{sup 3+} more than 60% by Y{sub 2}O{sub 3} surface coating. - Abstract: Novel Y{sub 2}O{sub 3} coated Y{sub 2}O{sub 3}:Eu{sup 3+} nanotubes with different coating ratios were synthesized successfully by a facile two-step process, including hydrothermal synthesis of Y(OH){sub 3} coated Y(OH){sub 3}:Eu{sup 3+} as precursors and then calcination ofmore » them at 1000 °C for 2 h. X-ray diffraction patterns and field emission scanning electron microscope images indicated these Y{sub 2}O{sub 3} coated Y{sub 2}O{sub 3}:Eu{sup 3+} phosphors possess tubular nanostructures. The photoluminescence properties of Y{sub 2}O{sub 3} coated Y{sub 2}O{sub 3}:Eu{sup 3+} were systematically investigated by photoluminescence spectra, and photoluminescence enhancement was observed after proper coating. In other words, the coating ratio played a crucial role in photoluminescence efficiency. When it was 1/9, the photoluminescence intensity of {sup 5}D{sub 0} → {sup 7}F{sub 2} emission (about 613 nm) was 60% higher than that of Y{sub 2}O{sub 3}: Eu{sup 3+} phosphors under 255 nm excitation. Therefore, surface coating may be an alternative route for enhanced photoluminescence properties of the Y{sub 2}O{sub 3}:Eu{sup 3+} red-emitting phosphor.« less

Thermodynamic Assessment of the Y2o3-yb2o3-zro2 System

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Liu, Zi-Kui; Kaufman, Larry; Zhang, Fan

2002-01-01

Yttria-zirconia (Y2O3-ZrO2) is the most widely used of the rare earth oxide-zirconia systems. There are numerous experimental studies of the phase boundaries in this system. In this paper, we assess these data and derive parameters for the solution models in this system. There is current interest in other rare earth oxide-zirconia systems as well as systems with several rare earth oxides and zirconia, which may offer improved properties over the Y2O3-ZrO2 system. For this reason, we also assess the ytterbia-zirconia (Yb2O3-ZrO2) and Y2O3-Yb2O3-ZrO2 system.

Scintillation properties of Gd3Al2Ga3O12:Ce3+ single crystal scintillators

NASA Astrophysics Data System (ADS)

Sakthong, Ongsa; Chewpraditkul, Weerapong; Wanarak, Chalerm; Kamada, Kei; Yoshikawa, Akira; Prusa, Petr; Nikl, Martin

2014-07-01

The scintillation properties of Gd3Al2Ga3O12:Ce3+ (GAGG:Ce) single crystals grown by the Czochralski method with 1 at% cerium in the melt were investigated and results were compared with so far published results in the literature. The light yield (LY) and energy resolution were measured using a XP5200B photomultiplier. Despite about twice higher LY for GAGG:Ce, the energy resolution is only slightly better than that of LuAG:Ce due to its worse intrinsic resolution and non-proportionality of LY. The LY dependences on the sample thickness and amplifier shaping time were measured. The estimated photofraction in pulse height spectra of 320 and 662 keV γ-rays and the total mass attenuation coefficient at 662 keV γ-rays were also determined and compared with the theoretical ones calculated using the WinXCom program.

A second metastable spin-ordered state on ferrimagnetic single crystal Cu2 OSeO 3

NASA Astrophysics Data System (ADS)

Chou, Chih Chieh; Huang, C. L.; Tseng, K. F.; Mukherjee, S.; Her, J. L.; Matsuda, Y. H.; Kindo, K.; Berger, H.; Yang, H. D.

2011-03-01

DC and AC susceptibilities were executed on ferrimagnetic single crystal Cu 2 OSe O3 under magnetic field (H) and hydrostatic pressure (P) circumstance. With increasing H , the ferrimagnetic transition at TC ~ 60 K tends to a higher temperature. Furthermore, the TC rises with a linear slope and magnetization is enhanced with increasing P . Features of the ladder shown in the M vs. H curve or the peak observed in the d M / d H vs. H curve are noted at HSF ~ 0.5 kOe, exhibiting a competing ordered state in magnetic fields below TC . Remarkably, another shoulder is observed at ~ 1 kOe in the d M / d H vs. H curve, revealing a metastable spin ordered state in Cu 2 OSe O3 . In addition, the novel state is retained and enhanced by applied pressure. However, at H up to 55 T, there is no more observable slop change in magnetization. These magnetic properties suggest a complex spin orientation in the spin-frustrated system Cu 2 OSe O3 .

Phase coexistence and domain configuration in Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 single crystal revealed by synchrotron-based X-ray diffractive three-dimensional reciprocal space mapping and piezoresponse force microscopy

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

Wang, Ruixue; Xu, Han; Yang, Bin

The crystalline phases and domain configuration in the morphotropic phase boundary composition Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 (PMN-0.34PT) single crystal have been investigated by synchrotronbased X-ray 3D Reciprocal Space Mapping (3D-RSM) and Piezoresponse Force Microscopy. The coexistence of tetragonal (T) and monoclinic MC phases in this PMN-0.34PT single crystal is confirmed. The affiliation of each diffraction spot in the 3D-RSM was identified with the assistance of qualitative simulation. Most importantly, the twinning structure between different domains in such a mixed phase PMN-PT crystal is firmly clarified, and the spatial distribution of different twin domains is demonstrated. In addition, the lattice parameters of T andmore » MC phases in PMN-0.34PT single crystal as well as the tilting angles of crystal lattices caused by the interfacial lattice mismatch are determined.« less

Effect of K3PO4 addition as sintering inhibitor during calcination of Y2O3 nanoparticles

NASA Astrophysics Data System (ADS)

Soga, K.; Okumura, Y.; Tsuji, K.; Venkatachalam, N.

2009-11-01

Erbium-doped yttrium oxide nanoparticle is one of the most important for fluorescence bioimaging under near infrared excitation. Particle size of it below 100 nm is an important requirement for a cellular bioimaging. However, the synthesis with such small particles is difficult at the calcination temperature above 1200 °C due to the sintering and crystal growth of the particles. In this study, yttrium oxide nanoparticles with average size of 30 nm were successfully synthesized by using K3PO4 as a sintering inhibitor during the calcination. A single phase of cubic Y2O3 as the resultant material was confirmed by XRD, which was also confirmed to emit a bright upconversion emission under 980-nm excitation. Improvement of chemical durability due to the introduction of phosphate group on the surface of the Y2O3 particles is also reported.

Growth and characterization of CaCu3Ti4O12 single crystals

NASA Astrophysics Data System (ADS)

Kim, Hui Eun; Yang, Sang-don; Lee, Jung-Woo; Park, Hyun Min; Yoo, Sang-Im

2014-12-01

The CaCu3Ti4O12 (CCTO) single crystals could be grown from the melt with the nominal composition of Ca:Cu:Ti=1:59:20 in a platinum (Pt) crucible using a self-flux method. The flux-grown CCTO single crystals have well-developed {100} habit planes, and their compositions are close to the ratio of Ca:Cu:Ti=1:3:4. Interestingly, flux-grown CCTO single crystals exhibited two different back reflection Laue patterns; one exhibited only [100] cubic Laue patterns, and the other showed not only [100] cubic Laue patterns but also the satellite spots related to the twin boundary, implying that twin-free CCTO single crystals can be grown by the self-flux method. Both the dielectric constants and losses of twinned CCTO single crystal are significantly higher than those of untwined CCTO crystal at relatively low frequency regime (<10 kHz), suggesting that the dielectric property is sensitive to the twin boundary.

Crystal structure and electrical conductivity of lanthanum-calcium chromites-titanates La 1-xCa xCr 1-yTi yO 3-δ ( x=0-1, y=0-1)

NASA Astrophysics Data System (ADS)

Vashook, V.; Vasylechko, L.; Zosel, J.; Gruner, W.; Ullmann, H.; Guth, U.

2004-10-01

Five series of perovskite-type compounds in the system La1-xCaxCr1-yTiyO3 with the nominal compositions y = 0 , x = 0 - 0.5 ; y = 0.2 , x = 0.2 - 0.8 ; y = 0.5 , x = 0.5 - 1.0 ; y = 0.8 , x = 0.6 - 1.0 and y = 1 , x = 0.8 - 1 were synthesized by a ceramic technique in air (final heating 1350 °C). On the basis of the X-ray analysis of the samples with (Ca/Ti)⩾1, the phase diagram of the CaTiO3-LaCrIIIO3-CaCrIVO3 quasi-ternary system was constructed. Extended solid solution with a wide homogeneity range is formed in the quasi-ternary system CaCrIVO3-CaTiO3-LaCrIIIO3. The solid solution La(1-x‧-y)Ca(x‧+y)CrIVx‧CrIII(1-x‧-y)TiyO3 exists by up to 0.6-0.7 mol fractions of CaCrIVO3 (x‧ < 0.6 - 0.7) at the experimental conditions. The crystal structure of the compounds is orthorhombic in the space group Pbnm at room temperature. The lattice parameters and the average interatomic distances of the samples within the solid solution ranges decrease uniformly with increasing Ca content. Outside the quasi-ternary system, the nominal compositions La0.1Ca0.9TiO3, La0.2Ca0.8TiO3, La0.4Ca0.6Cr0.2Ti0.8O3 and La0.3Ca0.7Cr0.2Ti0.8O3 in the system La1-xCaxCr1-yTiyO3 were found as single phases with an orthorhombic structure. In the temperature range between 850 and 1000 °C, the synthesized single-phase compositions are stable at pO2=6×10-16-0.21×105 Pa. Oxygen stoichiometry and electrical conductivity of the separate compounds were investigated as functions of temperature and oxygen partial pressure. The chemical stability of these oxides with respect to oxygen release during thermal dissociation decreases with increasing Ca-content. At 900 °C and oxygen partial pressure 1×10-15-0.21×105 Pa, the compounds with x > y (acceptor doped) are p-type semiconductors and those with x < y (donor doped) and x = y are n-type semiconductors. The type and level of electrical conductivity are functions of the concentration ratios of cations occupying the B-sites of the perovskite

Nd3+, Y3+-codoped SrF2 laser ceramics

NASA Astrophysics Data System (ADS)

Li, Weiwei; Mei, Bingchu; Song, Jinghong

2015-09-01

0.15 at.% Nd3+, 5 at.% Y3+-codoped SrF2 laser ceramic based on single crystal was prepared by extensive plastic deformation. Microstructure, optical and laser properties of the Nd3+, Y3+:SrF2 ceramic were investigated. The lasing of Nd3+, Y3+-codoped SrF2 ceramics with diode pumping have been observed and true CW laser operation around 1057 nm and 1050 nm was obtained with a slope efficiency of 31.9%. In particular, the fracture toughness of the ceramic is 0.98 MPa m1/2, which is approximately two times higher than that of single crystal.

Eu3+-doped (Y0.5La0.5)2O3: new nanophosphor with the bixbyite cubic structure

NASA Astrophysics Data System (ADS)

Đorđević, Vesna; Nikolić, Marko G.; Bartova, Barbora; Krsmanović, Radenka M.; Antić, Željka; Dramićanin, Miroslav D.

2013-01-01

New red sesquioxide phosphor, Eu3+-doped (Y0.5La0.5)2O3, was synthesized in the form of nanocrystalline powder with excellent structural ordering in cubic bixbyite-type, and with nanoparticle sizes ranging between 10 and 20 nm. Photoluminescence measurements show strong, Eu3+ characteristic, red emission ( x = 0.66 and y = 0.34 CIE color coordinates) with an average 5D0 emission lifetime of about 1.3 ms. Maximum splitting of the 7F1 manifold of the Eu3+ ion emission behaves in a way directly proportional to the crystal field strength parameter, and experimental results show perfect agreement with theoretical values for pure cubic sesquioxides. This could be used as an indicator of complete dissolution of Y2O3 and La2O3, showing that (Y0.5La0.5)2O3:Eu3+ behaves as a new bixbyite structure oxide, M2O3, where M acts as an ion having average ionic radius of constituting Y3+ and La3+. Emission properties of this new phosphor were documented with detailed assignments of Eu3+ energy levels at 10 K and at room temperature. Second order crystal field parameters were found to be B 20 = -66 cm-1 and B 22 = -665 cm-1 at 10 K and B 20 = -78 cm-1 and B 22 = -602 cm-1 at room temperature, while for the crystal field strength the value of 1495 cm-1 was calculated at 10 K and 1355 cm-1 at room temperature.

Crystal-field, exchange interactions and magnetism in pyrochlore ferromagnet R2V2O7 (R3+=Y, Lu)

NASA Astrophysics Data System (ADS)

Ali Biswas, A.; Jana, Y. M.

2013-03-01

The temperature dependence of the observed bulk magnetic susceptibility, magnetization, paramagnetic Curie temperature θCW, magnetic specific heat of ferromagnetic semi-conducting pyrochlore-based vanadate compounds Y2V2O7 and Lu2V2O7, which are the simplest of R2M2O7 pyrochlore series of oxides, are simulated and analyzed, simultaneously and consistently, within the frame work of the appropriate crystal-field (CF) theory and a mean-field approximation by introducing effective anisotropic molecular-field tensors and also taking account of appreciable spin-orbit coupling. The electronic and magnetic properties are correlated to the structural parameters. Ten-fold degenerate 2D term of 3d1 V4+-ions is split into five Kramers doublets with overall CF splitting Δ1≈2 eV and the total splitting of the 2T2g state Δ0≈0.4 eV under combined actions of octahedral CF, trigonal (D3d) distortion at V-site and spin-orbit coupling. The ground doublet is a well-isolated effectively spin s=1/2 state, characterized by the anisotropic g-tensors and directional magnetic moments. The degeneracy of the ground state is lifted by the spin-spin correlations among V4-tetrahedra at T∼170 K, which causes the formation of ferromagnetic clusters in these pyrochlores. The temperature dependence of the calculated directional site-susceptibilities shows that the V4+ ions have a substantial easy-axis single-ion anisotropy along local <111> axis of a given V4-tetrahedron in the magnetic phase where ferromagnetic clusters coexist with paramagnetic phase.

Numerical simulation and growth of Li2Zn2(MoO4)3 single crystals by the top seeded solution growth technique

NASA Astrophysics Data System (ADS)

Sukharev, V.; Sukhanova, E.; Mozhevitina, E.; Sadovsky, A.; Avetissov, I.

2017-06-01

Li2O - ZnO - MoO3 pseudo ternary system was used for the growth of Li2Zn2(MoO4)3 crystals by the top seeded solution growth technique in which MoO3 was used as a solvent. Properties of the melts (density, viscosity) have been experimentally measured at different temperatures and compositions of Li2O - ZnO - MoO3 pseudo ternary system. Heat mass transfer in the crystal growth setup was numerically simulated. Using the simulation results a real growth setup was made, Li2Zn2(MoO4)3 crystals were grown and their properties were studied.

Growth and optical properties of Dy:Y3Al5O12 crystal

NASA Astrophysics Data System (ADS)

Pan, Yuxin; Zhou, Shidong; Li, Dongzhen; Liu, Bin; Song, Qingsong; Liu, Jian; Liu, Peng; Ding, Yuchong; Wang, Xiaodan; Xu, Xiaodong; Xu, Jun

2018-02-01

High optical quality Dy:Y3Al5O12 (Dy:YAG) crystal has been grown by the Czochralski method. Absorption spectra, fluorescence spectra and fluorescence decay curve of Dy:YAG have been recorded at room temperature. The strongest emission of Dy:YAG crystal is near 583 nm, corresponding to the 4F9/2 → 6H13/2 transition. The Judd-Ofelt parameters Ω2, Ω4 and Ω6 were calculated to be 1.49 × 10-20 cm2, 0.94 × 10-20 cm2 and 3.20 × 10-20 cm2, respectively. The radiative transition rates, branching ratios and the emission cross sections were calculated. The fluorescence and radiative lifetimes are 0.40 ms and 1.02 ms, respectively, resulting in a quantum efficiency of 39.2%. The results indicate that the Dy:YAG crystal would be a promising yellow solid state laser material.

The crystal structure of galgenbergite-(Ce), CaCe2(CO3)4•H2O

NASA Astrophysics Data System (ADS)

Walter, Franz; Bojar, Hans-Peter; Hollerer, Christine E.; Mereiter, Kurt

2013-04-01

Galgenbergite-(Ce) from the type locality, the railroad tunnel Galgenberg between Leoben and St. Michael, Styria, Austria, was investigated. There it occurs in small fissures of an albite-chlorite schist as very thin tabular crystals building rosette-shaped aggregates associated with siderite, ancylite-(Ce), pyrite and calcite. Electron microprobe analyses gave CaO 9.49, Ce2O3 28.95, La2O3 11.70, Nd2O3 11.86, Pr2O3 3.48, CO2 30.00, H2O 3.07, total 98.55 wt.%. CO2 and H2O calculated by stoichiometry. The empirical formula (based on Ca + REE ∑3.0) is C{{a}_{1.00 }}{{( {C{{e}_{1.04 }}L{{a}_{0.42 }}N{{d}_{0.42 }}P{{r}_{0.12 }}} )}_{2.00 }}{{( {C{{O}_3}} )}_4}\\cdot {{H}_2}O , and the simplified formula is CaC{{e}_2}{{( {C{{O}_3}} )}_4}\\cdot {{H}_2}O . According to X-ray single crystal diffraction galgenbergite-(Ce) is triclinic, space group Poverline{1},a=6.3916(5) , b = 6.4005(4), c = 12.3898(9) Å, α = 100.884(4), β = 96.525(4), γ = 100.492(4)°, V = 483.64(6) Å3, Z = 2. The eight strongest lines in the powder X-ray diffraction pattern are [ d calc in Å/( I)/ hkl]: 5.052/(100)/011; 3.011/(70)/0-22; 3.006/(66)/004; 5.899/(59)/-101; 3.900/(51)/1-12; 3.125/(46)/-201; 2.526/(42)/022; 4.694/(38)/-102. The infrared absorption spectrum reveals H2O (OH-stretching mode at 3,489 cm-1, HOH bending mode at 1,607 cm-1) and indicates the presence of distinctly non-equivalent CO3-groups by double and quadruple peaks of their ν1, ν2, ν3 and ν4 modes. The crystal structure of galgenbergite-(Ce) was refined with X-ray single crystal data to R1 = 0.019 for 2,448 unique reflections ( I > 2 σ( I)) and 193 parameters. The three cation sites of the structure Ca(1), Ce(2) and Ce(3) have a modest mixed site occupation by Ca and small amount of REE (Ce, La, Pr, Nd) and vice versa. The structure is based on double layers parallel to (001), which are composed of Ca(1)Ce(2)(CO3)2 single layers with an ordered chessboard like arrangement of Ca and Ce, and with a roof tile

On the development of two characteristically different crystal morphology in SiO(2)-MgO-Al (2)O (3)-K (2)O-B (2)O (3)-F glass-ceramic system.

PubMed

Roy, Shibayan; Basu, Bikramjit

2009-01-01

The present work demonstrates how crystals with two different characteristic morphologies can be formed in SiO(2)-MgO-Al(2)O(3)-K(2)O-B(2)O(3)-F glass-ceramic system by adopting two sets of heat treatment experiments. In our study, single stage heat treatment experiments were performed at 1,000 degrees C for varying holding time of 8-24 h with 4 h time interval and as a function of temperature in the range of 1,000-1,120 degrees C with 40 degrees C temperature interval. The constant heating rate of 10 degrees C/min was employed for both sets of experiments. The microstructural changes were investigated using Fourier transformed infrared spectroscopy (FT-IR), SEM-EDS and XRD. For temperature variation batches, the microstructure is characterized by interlocked, randomly oriented mica plates ('house-of-cards' morphology). An important and new observation of complex crystal morphology is made in the samples heat treated at 1,000 degrees C for varying holding times. Such morphology appears to be the results of composite spherulitic-dendritic like growth of mica rods radiating from a central nucleus. The possible mechanism for such characteristic crystal growth morphology is discussed with reference to a nucleation-growth kinetics based model. The activation energy for crystal nucleation and Avrami index are computed to be 388 kJ/mol and 1.3 respectively, assuming Johnson-Mehl-Avrami model of crystallization. Another important result is that a maximum of around 70% of spherulitic-dendritic like crystal morphology can be obtained after heat treatment at 1,000 degrees C for 24 h, while a lower amount (approximately 58%) of interlocked plate like mica crystals is formed after heat treatment at 1,040 degrees C for 4 h.

Wavelength dependence of Verdet constant of Tb{sup 3+}:Y{sub 2}O{sub 3} ceramics

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

Snetkov, I. L., E-mail: snetkov@appl.sci-nnov.ru; Palashov, O. V.; Permin, D. A.

2016-04-18

Samples of the magneto-active material—Tb{sup 3+}:Y{sub 2}O{sub 3} ceramics with Tb{sup 3+} ion concentrations of 10%, 20%, 30%, and 100% (Tb{sub 2}O{sub 3})—were prepared and studied. The wavelength dependence of Verdet constant in the 380 nm–1750 nm range was approximated for all investigated ceramic samples and was predicted for a pure Tb{sub 2}O{sub 3} material. Tb{sub 2}O{sub 3} ceramics demonstrates a more than three times higher Verdet constant in comparison with terbium gallium garnet crystal or ceramics. The linear dependence of the Verdet constant on Tb{sup 3+} ion concentration in the Tb{sup 3+}:Y{sub 2}O{sub 3} ceramics was demonstrated. The obtained data willmore » be useful for fabricating magneto-optical elements of Faraday devices based on Tb{sup 3+}:Y{sub 2}O{sub 3} with arbitrary Tb{sup 3+} ion concentration operating at room temperature in the wavelength range of 380 nm–1750 nm.« less

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

Y 3-xMg 2AlSi 2O 12: Cex3+ phosphors - prospective for warm-white light emitting diodes

NASA Astrophysics Data System (ADS)

Katelnikovas, Arturas; Bareika, Tomas; Vitta, Pranciškus; Jüstel, Thomas; Winkler, Holger; Kareiva, Aivaras; Žukauskas, Artūras; Tamulaitis, Gintautas

2010-07-01

Y 3-xMg 2AlSi 2O 12: Cex3+ (YMASG:Ce) phosphors were synthesized by sol-gel combustion technique at different temperatures from 1400 to 1550 °C. Samples with x = 0.015, 0.03, 0.045, and 0.06 were fabricated and characterized using powder X-ray diffraction (XRD), photoluminescence spectroscopy, and fluorescence lifetime measurements in frequency domain. XRD patterns confirmed single-phase garnet crystal structure for all the samples independently of their substitutional level and annealing temperature. In respect to Y 3Al 5O 12:Ce 3+ (YAG:Ce) phosphor, which was synthesized for comparison by a different sol-gel procedure, the photoluminescence band of these garnets is red shifted, indicating a prospective for application of this novel phosphor in warm-white light emitting diodes (LEDs). The luminescence decays bi-exponentially. The main component has a characteristic decay time decreasing from 72 to of 50 ns with increasing sintering temperature and cerium content, while ˜2% of the excitation decays with a characteristic decay time of ˜8 ns.

Crystal chemistry of hydrous phases in the Al2O3-Fe2O3-H2O system: implications for water cycle in the deep lower mantle

NASA Astrophysics Data System (ADS)

Zhang, L.

2016-12-01

Hydrous minerals play an important role in the transportation and storage of water in the Earth's interior. Recently a pyrite-structured iron oxide (FeO2) (P-phase) was found stable at 76 GPa and 1800 K [1] and this discovery has brought new insights into the H2-O2 cycles in the deep mantle. In this study, we perform in situ synchrotron X-ray experiments in the Al2O3-Fe2O3-H2O system in a laser-heated diamond anvil cell (DAC) at P-T conditions in the deep lower mantle. The new results added more complexity to the H2-O2/H2O cycles in the deep lower mantle. The symmetry and unit-cell parameters of each phase in the run products were determined using the multigrain approach [2]. On the other hand, the d-H solid solution AlOOH-MgSiO2(OH)2 is the stable hydrous phase coexisting with bridgmanite or post-perovskite under equilibrium P-T conditions to the deepest lower mantle [3]. The detailed crystal chemistry of the newly found hydrous phases and its relations to the d-H phase have been investigated using both first-principles calculations and experiments, providing new understanding to the hydration mechanism and water storage in the deep mantle. It is worth mentioning that recent development in high pressure multigrain method has realized separation of each individual phase in a multiphase assemblage and even allowed in situ crystal structure determination of a minor phase in the assemblage contained in a DAC [4]. [1] Q. Hu, D. Y. Kim, W. Yang, L. Yang, Y. Meng, L. Zhang, and H. K. Mao, Nature 534, 241 (2016). [2] H. O. Sørensen et al., Zeitschrift für Kristallographie 227, 63 (2012). [3] I. Ohira, E. Ohtani, T. Sakai, M. Miyahara, N. Hirao, Y. Ohishi, and M. Nishijima, Earth and Planetary Science Letters 401, 12 (2014). [4] L. Zhang, D. Popov, Y. Meng, J. Wang, C. Ji, B. Li, and H.-k. Mao, American Mineralogist 101, 231 (2016).

Effect of Slag Composition on the Crystallization Kinetics of Synthetic CaO-SiO2-Al2O3-MgO Slags

NASA Astrophysics Data System (ADS)

Esfahani, Shaghayegh; Barati, Mansoor

2018-04-01

The crystallization kinetics of CaO-SiO2-Al2O3-MgO (CSAM) slags was studied with the aid of single hot thermocouple technique (SHTT). Kinetic parameters such as the Avrami exponent ( n), rate coefficient ( K), and effective activation energy of crystallization ( E A ) were obtained by kinetic analysis of data obtained from in situ observation of glassy to crystalline transformation and image analysis. Also, the dependence of nucleation and growth rates of crystalline phases were quantified as a function of time, temperature, and slag basicity. Together with the observations of crystallization front, they facilitated establishing the dominant mechanisms of crystallization. In an attempt to predict crystallization rate under non-isothermal conditions, a mathematical model was developed that employs the rate data of isothermal transformation. The model was validated by reproducing an experimental continuous cooling transformation diagram purely from isothermal data.

High-pressure investigations of yttrium(III) oxoarsenate(V): Crystal structure and luminescence properties of Eu3+-doped scheelite-type Y[AsO4] from xenotime-type precursors

NASA Astrophysics Data System (ADS)

Ledderboge, Florian; Nowak, Jan; Massonne, Hans-Joachim; Förg, Katharina; Höppe, Henning A.; Schleid, Thomas

2018-07-01

Colourless, water- and air-stable single crystals of yttrium(III) oxoarsenate(V) Y[AsO4] in the xenotime-type crystal structure were prepared by the reaction of yttrium sesquioxide (Y2O3) dissolved in aqueous nitric acid (13%) with a solution of arsenic(V) oxide hydrate (As2O5·3H2O) and subsequent neutralization with 1 M caustic soda. Y[AsO4] crystallizes tetragonally in the space group I41/amd with the lattice parameters a = 704.63(6) and c = 628.94(5) pm for Z = 4 and is isotypic to the minerals xenotime RE[PO4] (RE: mainly Y and Yb) and chernovite RE[AsO4] (RE: mainly Y and Ce). This xenotime-type yttrium compound was used as precursor in a high-pressure experiment (20 kbar) at 700 °C to create a new tetragonal modification of Y[AsO4]. It shows the scheelite-type structure (space group: I41/a) with the lattice parameters a = 498.23(4) and c = 1120.71(9) pm for Z = 4, named after the mineral scheelite (Ca[WO4]). Both tetragonal structures are characterized by only one crystallographically unique position for each of the Y3+, As5+ and O2- ions with distances of d(Y-O) = 232 and 241 pm (C.N. = 8) as well as d(As-O) = 169 pm (C.N. = 4) in the case of the scheelite-type structure. The xenotime-type compound shows an unexpected slight decrease in average bond lengths for the yttrium to oxygen (d(Y-O) = 230 and 241 pm, C.N. = 8) as well as for the arsenic to oxygen distances (d(As-O) = 168 pm, C.N. = 4), accompanied by a drastic density increase from Dx = 4.85 (xenotime type) to Dx = 5.44 g • cm-3 (scheelite type). Luminescence spectroscopic measurements of the Eu3+-doped Y[AsO4] samples, obtained in experiments at similar conditions as for the pure compounds, show a bright, reddish lighting for the scheelite type, which does not occur for the xenotime type of yttrium(III) oxoarsenate(V).

Calculation of Phase Equilibria in the Y2O3-Yb2O3-ZrO2 System

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Liu, Zi-Kui; Kaufman, Larry; Zhang, Fan

2001-01-01

Rare earth oxide stabilized zirconias find a wide range of applications. An understanding of phase equilibria is essential to all applications. In this study, the available phase boundary data and thermodynamic data is collected and assessed. Calphad-type databases are developed to completely describe the Y2O3-ZrO2, Yb2O3-ZrO2, and Y2O3-Yb2O3 systems. The oxide units are treated as components and regular and subregular solution models are used. The resultant calculated phase diagrams show good agreement with the experimental data. Then the binaries are combined to form the database for the Y2O3-Yb2O3-ZrO2 psuedo-ternary.

Single crystal growth, magnetic and thermal properties of perovskite YFe0.6Mn0.4O3 single crystal

NASA Astrophysics Data System (ADS)

Xie, Tao; Shen, Hui; Zhao, Xiangyang; Man, Peiwen; Wu, Anhua; Su, Liangbi; Xu, Jiayue

2016-11-01

High quality YFe0.6Mn0.4O3 single crystal was grown by floating zone technique using a four-mirror-image-furnace under flowing air. Powder X-ray diffraction gives well evidence that the specimen has an orthorhombic structure, with space group Pbnm. Temperature dependence of the magnetizations of YFe0.6Mn0.4O3 single crystal were studied under ZFC and FC modes in the temperature range from 5 K to 400 K. A clear spin reorientation transition behavior (Γ4→Γ1) is observed in the temperature range of 322-316 K, due to the substitution of Mn at the Fe site of YFeO3. Its Néel temperature is around 385 K. Moreover, the spin reorientation is verified by the change of magnetic hysteresis loops of the sample along [001] axis in the temperature range of 50-385 K. The thermal properties of the sample were measured by the differential scanning calorimeter (DSC) from 300 K to 500 K, which also clearly appear anomaly in the spin reorientation region.

Synthesis and characterization of polymer eight-coordinate (enH 2)[Y III(pdta)(H 2O)] 2·10H 2O as well as the interaction of [Y III(pdta)(H 2O)] 22- with BSA

NASA Astrophysics Data System (ADS)

Liu, Bin; Wang, Jun; Wang, Xin; Liu, Bing-Mi; He, Ling-Ling; Xu, Shu-Kun

2010-12-01

The eight-coordinate (enH 2)[Y III(pdta)(H 2O)] 2·10H 2O (en = ethylenediamine and H 4pdta = 1,3-propylenediamine- N, N, N', N'-tetraacetic acid) was synthesized, meanwhile its molecular and crystal structures were determined by single-crystal X-ray diffraction technology. The interaction between [Y III(pdta)(H 2O)] 22- and bovine serum albumin (BSA) was investigated by UV-vis and fluorescence spectra. The results indicate that [Y III(pdta)(H 2O)] 22- quenched effectively the intrinsic fluorescence of BSA via a static quenching process with the binding constant ( Ka) of the order of 10 4. Meanwhile, the binding and damaging sites to BSA molecules were also estimated by synchronous fluorescence. Results indicate that the hydrophobic environments around Trp and Tyr residues were all slightly changed. The thermodynamic parameters (Δ G = -25.20 kJ mol -1, Δ H = -26.57 kJ mol -1 and Δ S = -4.58 J mol -1 K -1) showed that the reaction was spontaneous and exothermic. What is more, both Δ H and Δ S were negative values indicated that hydrogen bond and Van der Waals forces were the predominant intermolecular forces between [Y III(pdta)(H 2O)] 22- and BSA.

Synthesis and Characterization of Yttria-Stabilized Zirconia Nanoparticles Doped with Ytterbium and Gadolinium: ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3

NASA Astrophysics Data System (ADS)

Bahamirian, M.; Hadavi, S. M. M.; Rahimipour, M. R.; Farvizi, M.; Keyvani, A.

2018-03-01

Defect cluster thermal barrier coatings (TBCs) are attractive alternatives to Yttria-stabilized zirconia (YSZ) in advanced applications. In this study, YSZ nanoparticles doped with ytterbium and gadolinium (ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3 (ZGYbY)) were synthesized through a chemical co-precipitation and calcination method, and characterized by in situ high-temperature X-ray diffraction analysis in the temperature range of 25 °C to 1000 °C (HTK-XRD), thermogravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM). Precise cell parameters of t-prime phase and the best zirconia phase for TBC applications were calculated by Cohen's and Rietveld refinement methods. Optimum crystallization temperature of the precursor powder was found to be 1000 °C. Furthermore, FE-SEM results for the calcined ZGYbY powders indicated orderly particles of uniform shape and size with a small tendency toward agglomeration. Average lattice thermal expansion coefficient in the temperature range of 25 °C to 1000 °C was determined to be 31.71 × 10-6 K-1.

Synthesis and Characterization of Yttria-Stabilized Zirconia Nanoparticles Doped with Ytterbium and Gadolinium: ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3

NASA Astrophysics Data System (ADS)

Bahamirian, M.; Hadavi, S. M. M.; Rahimipour, M. R.; Farvizi, M.; Keyvani, A.

2018-06-01

Defect cluster thermal barrier coatings (TBCs) are attractive alternatives to Yttria-stabilized zirconia (YSZ) in advanced applications. In this study, YSZ nanoparticles doped with ytterbium and gadolinium (ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3 (ZGYbY)) were synthesized through a chemical co-precipitation and calcination method, and characterized by in situ high-temperature X-ray diffraction analysis in the temperature range of 25 °C to 1000 °C (HTK-XRD), thermogravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM). Precise cell parameters of t-prime phase and the best zirconia phase for TBC applications were calculated by Cohen's and Rietveld refinement methods. Optimum crystallization temperature of the precursor powder was found to be 1000 °C. Furthermore, FE-SEM results for the calcined ZGYbY powders indicated orderly particles of uniform shape and size with a small tendency toward agglomeration. Average lattice thermal expansion coefficient in the temperature range of 25 °C to 1000 °C was determined to be 31.71 × 10-6 K-1.

Study on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 single crystal with nano-patterned composite electrode

PubMed Central

Chang, Wei-Yi; Huang, Wenbin; Bagal, Abhijeet; Chang, Chih-Hao; Tian, Jian; Han, Pengdi; Jiang, Xiaoning

2013-01-01

Effect of nano-patterned composite electrode and backswitching poling technique on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 was studied in this paper. Composite electrode consists of Mn nano-patterns with pitch size of 200 nm, and a blanket layer of Ti/Au was fabricated using a nanolithography based lift-off process, heat treatment, and metal film sputtering. Composite electrode and backswitching poling resulted in 27% increase of d33 and 25% increase of dielectric constant, and we believe that this is attributed to regularly defined nano-domains and irreversible rhombohedral to monoclinic phase transition in crystal. The results indicate that nano-patterned composite electrode and backswitching poling has a great potential in domain engineering of relaxor single crystals for advanced devices. PMID:24170960

A new series of mixed oxalates MM'(C 2O 4) 3(H 2O) 3· nH 2O (M = Cd, Hg, Pb; M' = Zr, Hf) based on eight-fold coordinated metals: Synthesis, crystal structure from single-crystal and powder diffraction data and thermal behaviour

NASA Astrophysics Data System (ADS)

Gavilan, Elisabeth; Audebrand, Nathalie; Jeanneau, Erwann

2007-11-01

A new series of mixed oxalates MM'(C 2O 4) 3(H 2O) 3· nH 2O (M = Cd, Hg, Pb; M' = Zr, Hf) has been prepared. The crystal structures have been solved from single-crystal and powder diffraction data. The isotypical compounds crystallise with space group P2 1/ c (No. 14). The structures consist of honeycomb layers formed by eight-fold coordinated metals, in a distorted square-based antiprismatic conformation, connected together via oxalates which act as bidentate ligands and also as monodentate in a less-common μ3-bridging mode. Sheets are built from two shifted honeycomb layers and linked to each other through a hydrogen network. The resulting frameworks of the series display a compact two-dimensional arrangement of polyhedra MO 8 and M'O 8. Weakly-bonded water molecules are located between and within the sheets. Comparisons with the 3D open-framework structures of related metal oxalates are made. The dehydration processes occur in three or four steps. The final products are MO, M'O 2 and PbZrO 3 resulting from the sublimation of PbO in air. The size of PbZrO 3 crystallites, which are on average isotropic, has been evaluated to be 1055 Å from line-broadening analysis.

Photoelectron spectroscopy and density functional theory study of TiAlO(y) (-) (y=1-3) and TiAl(2)O(y) (-) (y=2-3) clusters.

PubMed

Zhang, Zeng-Guang; Xu, Hong-Guang; Zhao, Yuchao; Zheng, Weijun

2010-10-21

Small titanium-aluminum oxide clusters, TiAlO(y) (-) (y=1-3) and TiAl(2)O(y) (-) (y=2-3), were studied by using anion photoelectron spectroscopy. The adiabatic detachment energies of TiAlO(y) (-) (y=1-3) were estimated to be 1.11±0.05, 1.70±0.08, and 2.47±0.08eV based on their photoelectron spectra; those of TiAl(2)O(2) (-) and TiAl(2)O(3) (-) were estimated to be 1.17±0.08 and 2.2±0.1eV, respectively. The structures of these clusters were determined by comparison of density functional calculations with the experimental results. The structure of TiAlO(-) is nearly linear with the O atom in the middle. That of TiAlO(2) (-) is a kite-shaped structure. TiAlO(3) (-) has a kite-shaped TiAlO(2) unit with the third O atom attaching to the Ti atom. TiAl(2)O(2) (-) has two nearly degenerate Al-O-Ti-O-Al chain structures that can be considered as cis and trans forms. TiAl(2)O(3) (-) has two low-lying isomers, kite structure and book structure. The structures of these clusters indicate that the Ti atom tends to bind to more O atoms.

STM/STS Study of LixCoO2 Single Crystals

NASA Astrophysics Data System (ADS)

Iwaya, Katsuya; Minato, Taketoshi; Miyoshi, Kiyotaka; Takeuchi, Jun; Kim, Yousoo; Hitosugi, Taro

2012-02-01

We have performed low temperature scanning tunneling microscopy/spectroscopy (STM/STS) measurements on LixCoO2 (x=0.66) single crystal surfaces. A (1x1) hexagonal lattice was clearly observed and found to be moved by changing bias-voltage polarity, indicating that this could be associated with Li ions on the surface. Under the (1x1) hexagonal lattice, we imaged almost randomly distributed bright dots that were strongly dependent on bias-voltage, with insulating spectroscopic features. Different area on the surface showed a (2x2) hexagonal lattice that could be related to an ordering of Co^3+ and Co^4+ ions. These results suggest the electronic structure of LixCoO2 surface is inhomogeneous possibly due to segregation of Li ions.

Piezoelectric energy harvesting based on shear mode 0.71Pb(Mg(1/3)Nb(2/3))O3-0.29PbTiO3 single crystals.

PubMed

Ren, Bo; Or, Siu Wing; Wang, Feifei; Zhao, Xiangyong; Luo, Haosu; Li, Xiaobing; Zhang, Qinhui; Di, Wenning; Zhang, Yaoyao

2010-06-01

In this paper we theoretically and experimentally present a nonresonant vibration energy harvesting device based on the shear mode of 0.71Pb(Mg(1/3)Nb(2/3))O3-0.29PbTiO3 single crystals. The electrical properties of the energy harvesting device were evaluated using an analytical method. Good consistency was obtained between the analytical and experimental results. Under a mass load of 200 g, a peak voltage of 11.3 V and maximum power of 0.70 mW were obtained at 500 Hz when connecting a matching load resistance of 91 komega. A high output could always be obtained within a very wide frequency range. The results demonstrate the potential of the device in energy harvesting applied to low-power portable electronics and wireless sensors.

Growth of single crystals of BaFe12O19 by solid state crystal growth

NASA Astrophysics Data System (ADS)

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

2016-10-01

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

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

PubMed Central

Sun, Enwei; Cao, Wenwu

2014-01-01

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

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

PubMed

Sun, Enwei; Cao, Wenwu

2014-08-01

In the past decade, domain engineered relaxor-PT ferroelectric single crystals, including (1- x )Pb(Mg 1/3 Nb 2/3 )O 3 - x PbTiO 3 (PMN-PT), (1- x )Pb(Zn 1/3 Nb 2/3 )O 3 - x PbTiO 3 (PZN-PT) and (1- x - y )Pb(In 1/2 Nb 1/2 )O 3 - y Pb(Mg 1/3 Nb 2/3 )O 3 - x PbTiO 3 (PIN-PMN-PT), with compositions near the morphotropic phase boundary (MPB) have triggered a revolution in electromechanical devices owing to their giant piezoelectric properties and ultra-high electromechanical coupling factors. Compared to traditional PbZr 1- x Ti x O 3 (PZT) ceramics, the piezoelectric coefficient d 33 is increased by a factor of 5 and the electromechanical coupling factor k 33 is increased from < 70% to > 90%. Many emerging rich physical phenomena, such as charged domain walls, multi-phase coexistence, domain pattern symmetries, etc., have posed challenging fundamental questions for scientists. The superior electromechanical properties of these domain engineered single crystals have prompted the design of a new generation electromechanical devices, including sensors, transducers, actuators and other electromechanical devices, with greatly improved performance. It took less than 7 years from the discovery of larger size PMN-PT single crystals to the commercial production of the high-end ultrasonic imaging probe "PureWave". The speed of development is unprecedented, and the research collaboration between academia and industrial engineers on this topic is truly intriguing. It is also exciting to see that these relaxor-PT single crystals are being used to replace traditional PZT piezoceramics in many new fields outside of medical imaging. The new ternary PIN-PMN-PT single crystals, particularly the ones with Mn-doping, have laid a solid foundation for innovations in high power acoustic projectors and ultrasonic motors, hinting another revolution in underwater SONARs and miniature actuation devices. This article intends to provide a comprehensive review on the development of relaxor

Crystal Growth and Scintillation Properties of Ce Doped Gd3Ga,Al5O12 Single Crystals

NASA Astrophysics Data System (ADS)

Kamada, Kei; Yanagida, Takayuki; Pejchal, Jan; Nikl, Martin; Endo, Takanori; Tsutsumi, Kousuke; Fujimoto, Yutaka; Fukabori, Akihiro; Yoshikawa, Akira

2012-10-01

Ce1%, 2% and 3% doped Gd3(Ga,Al)5O12 (GAGG) single crystals were grown by the Cz method. Luminescence and scintillation properties were measured. Light yield change along the growth direction and effects of Ce concentration on scintillation properties in Ce:GAGG were studied. Ce3+ 5d-4f emission within 520-530 nm was observed in the Ce:GAGG crystals. The Ce1%:GAGG sample with 3×3×1 mm size showed the highest light yield of 46000 photon/MeV. The energy resolution was 7.8%@662 keV. With increasing solidification fraction, the LY were decreased. It is proposed that the increase of Ga concentration along the growth direction is the main cause of the decrease of LY. The scintillation decay times were accelerated with increasing Ce concentration in the Ce:GAGG crystals. The scintillation decay times were 92.0 ns, 79.1 ns and 68.3 ns in the Ce1, 2 and 3% GAGG, respectively.

ZnTeO{sub 3} crystal growth by a modified Bridgman technique

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

Nawash, Jalal M., E-mail: nawashj@uww.edu; Lynn, Kelvin G.

2014-12-15

Highlights: • ZnTeO{sub 3} single crystals were grown for the first time by a modified Bridgman method. • The growth is still possible in a system that lacks congruent melting. • A growth is best when melt is exposed to a steeper axial thermal gradient. • Optical and electrical properties were investigated for the grown crystals. - Abstract: Zinc Tellurite (ZnTeO{sub 3}) crystals were grown for the first time using a modified Bridgman method with a 2.5 kHz radio frequency (RF) furnace. Single crystal growth of ZnTeO{sub 3} was hindered by many complicating factors, such as the evaporation of TeO{submore » 2} above 700 °C and the formation of more than one phase during crystal growth. While there were several successful runs that produced ZnTeO{sub 3} single crystals, it was found that large (≥10 cm{sup 3}) single ZnTeO{sub 3} crystals resulted when the crucible was exposed to a steeper vertical thermal gradient and when the temperature of the melt was raised to at least 860 °C. The results of powder X-ray diffraction (XRD) patterns were in accordance with the X-ray powder diffraction file (PDF) for ZnTeO{sub 3}. Some optical, electrical and structural properties of ZnTeO{sub 3} single crystals were reported in this paper.« less

Ultrahigh energy density harvested from domain-engineered relaxor ferroelectric single crystals under high strain rate loading

NASA Astrophysics Data System (ADS)

Shkuratov, Sergey I.; Baird, Jason; Antipov, Vladimir G.; Talantsev, Evgueni F.; Chase, Jay B.; Hackenberger, Wesley; Luo, Jun; Jo, Hwan R.; Lynch, Christopher S.

2017-04-01

Relaxor ferroelectric single crystals have triggered revolution in electromechanical systems due to their superior piezoelectric properties. Here the results are reported on experimental studies of energy harvested from (1-y-x)Pb(In1/2Nb1/2)O3-(y)Pb(Mg1/3Nb2/3)O3-(x)PbTiO3 (PIN-PMN-PT) crystals under high strain rate loading. Precise control of ferroelectric properties through composition, size and crystallographic orientation of domains made it possible to identify single crystals that release up to three times more electric charge density than that produced by PbZr0.52Ti0.48O3 (PZT 52/48) and PbZr0.95Ti0.05O3 (PZT 95/5) ferroelectric ceramics under identical loading conditions. The obtained results indicate that PIN-PMN-PT crystals became completely depolarized under 3.9 GPa compression. It was found that the energy density generated in the crystals during depolarization in the high voltage mode is four times higher than that for PZT 52/48 and 95/5. The obtained results promise new single crystal applications in ultrahigh-power transducers that are capable of producing hundreds kilovolt pulses and gigawatt-peak power microwave radiation.

Ultrahigh energy density harvested from domain-engineered relaxor ferroelectric single crystals under high strain rate loading

PubMed Central

Shkuratov, Sergey I.; Baird, Jason; Antipov, Vladimir G.; Talantsev, Evgueni F.; Chase, Jay B.; Hackenberger, Wesley; Luo, Jun; Jo, Hwan R.; Lynch, Christopher S.

2017-01-01

Relaxor ferroelectric single crystals have triggered revolution in electromechanical systems due to their superior piezoelectric properties. Here the results are reported on experimental studies of energy harvested from (1-y-x)Pb(In1/2Nb1/2)O3–(y)Pb(Mg1/3Nb2/3)O3–(x)PbTiO3 (PIN-PMN-PT) crystals under high strain rate loading. Precise control of ferroelectric properties through composition, size and crystallographic orientation of domains made it possible to identify single crystals that release up to three times more electric charge density than that produced by PbZr0.52Ti0.48O3 (PZT 52/48) and PbZr0.95Ti0.05O3 (PZT 95/5) ferroelectric ceramics under identical loading conditions. The obtained results indicate that PIN-PMN-PT crystals became completely depolarized under 3.9 GPa compression. It was found that the energy density generated in the crystals during depolarization in the high voltage mode is four times higher than that for PZT 52/48 and 95/5. The obtained results promise new single crystal applications in ultrahigh-power transducers that are capable of producing hundreds kilovolt pulses and gigawatt-peak power microwave radiation. PMID:28440336

Crystal structure and magnetic properties of Mn substituted ludwigite Co 3O 2BO 3

NASA Astrophysics Data System (ADS)

Knyazev, Yu. V.; Ivanova, N. B.; Kazak, N. V.; Platunov, M. S.; Bezmaternykh, L. N.; Velikanov, D. А.; Vasiliev, А. D.; Ovchinnikov, S. G.; Yurkin, G. Yu.

2012-03-01

The needle shape single crystals Co3-x MnxO2BO3 with ludwigite structure have been prepared. According to the X-ray diffraction data the preferable character of distinct crystallographic positions occupation by Mn ions is established. Magnetization field and temperature dependencies are measured. Paramagnetic Curie temperature value Θ=-100 K points out the predominance of antiferromagnetic interactions. Spin-glass magnetic ordering takes the onset at TN=41 K. The crystallographic and magnetic properties of Co3O2BO3:Mn are compared with the same for the isostructural analogs Co3O2BO3 and CoO2BO3:Fe.

Phase equilibria, crystal structure and properties of complex oxides in the Nd{sub 2}O{sub 3}–SrO–CoO system

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

Aksenova, T.V.; Efimova, T.G.; Lebedev, O.I.

2017-04-15

The phase equilibria in the ½Nd{sub 2}O{sub 3}–SrO–CoO system were systematically studied at 1373 K in air. The intermediate phases formed in the ½Nd{sub 2}O{sub 3}–SrO–CoO system at 1373 K in air are: Nd{sub 1-x}Sr{sub x}CoO{sub 3-δ} (0.0≤x≤0.5 with orthorhombic structure, sp. gr. Pbnm and 0.6≤x≤0.95 whose structure was detected as cubic according to XRD sp. gr. Pm3m, but shown to be tetragonal by TEM due to the oxygen vacancy ordering), Nd{sub 2-y}Sr{sub y}CoO{sub 4-δ} (0.6≤y≤1.1 with tetragonal K{sub 2}NiF{sub 4}-type structure, sp. gr. I4/mmm) and Nd{sub 2-z}Sr{sub z}O{sub 3} (0.0≤z≤0.15 with hexagonal structure, sp. gr. P-3m1). The unit cellmore » parameters for the single phase samples were refined by the Rietveld analysis. The changes of oxygen content in Nd{sub 1-x}Sr{sub x}CoO{sub 3-δ} (0.6≤x≤0.95) and Ruddlesden-Popper oxide Nd{sub 2-y}Sr{sub y}CoO{sub 4-δ} were examined by TGA. All were found to be oxygen deficient phases. High-temperature dilatometry allows calculating the thermal expansion coefficient and evaluating the chemical expansion coefficient at high temperature. The projection of isothermal-isobaric phase diagram for the Nd–Sr–Co–O system at 1373 K in air to the compositional triangle of metallic components has been constructed. The phase equilibria in the studied Nd–Sr–Co–O system were compared to La–Sr–Co–O and Nd–M–Co–O (M=Ca and Ba). - Graphical abstract: Crystal structure of vacancy ordered supercell for Nd{sub 0.2}Sr{sub 0.8}CoO{sub 3-δ} and projection of phase diagram for the Nd–Sr–Co–O system onto the triangle edge of metallic components at 1373 K in air. - Highlights: • The diagram for the Nd–Sr–Co–O system at 1373 K in air has been constructed. • The crystal structure of Nd{sub 1-x}Sr{sub x}CoO{sub 3-δ} and Nd{sub 2-y}Sr{sub y}CoO{sub 4±δ} was refined. • The formation of superstructure due to the oxygen vacancy ordering was proved. • The changes of

Investigation and characterization of ZnO single crystal microtubes

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

Al-Naser, Qusay A.H.; Zhou, Jian, E-mail: jianzhou@whut.edu.cn; Liu, Guizhen

2016-04-15

Morphological, structural, and optical characterization of microwave synthesized ZnO single crystal microtubes were investigated in this work. The structure and morphology of the ZnO microtubes are characterized using X-ray diffraction (XRD), single crystal diffraction (SCD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The results reveal that the as-synthesized ZnO microtube has a highly regular hexagonal cross section and smooth surfaces with an average length of 650–700 μm, an average outer diameter of 50 μm and wall thickness of 1–3 μm, possessing a single crystal wurtzite hexagonal structure. Optical properties of ZnOmore » single crystal microtubes were investigated by photoluminescence (PL) and ultraviolet-visible (UV-vis) absorption techniques. Room-temperature PL spectrum of the microtube reveal a strong UV emission peak at around 375.89 nm and broad and a weak visible emission with a main peak identified at 577 nm, which was assigned to the nearest band-edge emission and the deep-level emission, respectively. The band gap energy of ZnO microtube was found to be 3.27 eV. - Highlights: • ZnO microtube length of 650–700 μm, diameter of 50 μm, wall thickness of 1–3 μm • ZnO microtube possesses a single crystal wurtzite hexagonal structure. • The crystal system is hexahedral oriented along a-axis with indices of (100). • A strong and sharp UV emission at 375.89 nm (3.29 eV) • One prominent absorption band around 378.88 nm (3.27 eV)« less

Modifying the Surface of γ-Al2 O3 with Y2 Sn2 O7 Pyrochlore: Monolayer Dispersion Behaviour of Composite Oxides.

PubMed

Xu, Xianglan; Liu, Fang; Tian, Jinshu; Peng, Honggen; Liu, Wenming; Fang, Xiuzhong; Zhang, Ning; Wang, Xiang

2017-06-20

To investigate the dispersion behaviour of composite oxides on supports, and to obtain better supports for Pd for CO oxidation, a series of Y 2 Sn 2 O 7 /Al 2 O 3 composite oxides with different Y 2 Sn 2 O 7 loadings were prepared by a deposition-precipitation method. XRD and X-ray photoelectron spectroscopic extrapolation methods revealed that, similar to single-component metal oxides, composite oxides can also disperse spontaneously on support surfaces to form a monolayer with a certain capacity. The monolayer dispersion capacity/threshold for Y 2 Sn 2 O 7 on the surface of γ-Al 2 O 3 is 0.109 mmol per 100 m 2 γ-Al 2 O 3 , corresponding to 7.2 wt % Y 2 Sn 2 O 7 loading. This is the first work to demonstrate monolayer dispersion of a composite oxide on a support. After combining Y 2 Sn 2 O 7 with γ-Al 2 O 3 , active oxygen species can be introduced onto the catalyst surfaces. Thus, the interaction between Pd and the support is strengthened, the dispersion of Pd is improved in comparison with the single-component Y 2 Sn 2 O 7 support, and a synergistic effect is induced between Pd and the composite support, which is beneficial to catalyst activity. By tuning the γ-Al 2 O 3 surface with different amounts of pyrochlore Y 2 Sn 2 O 7 , CO oxidation activity on 1 % Pd/Y 2 Sn 2 O 7 /Al 2 O 3 was improved. These findings may provide new insights into the design and preparation of effective supported noble metal catalysts with lower contents of noble metals. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phase coexistence and domain configuration in Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-0.34PbTiO{sub 3} single crystal revealed by synchrotron-based X-ray diffractive three-dimensional reciprocal space mapping and piezoresponse force microscopy

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

Wang, Ruixue; Yang, Bin, E-mail: binyang@hit.edu.cn; Sun, Enwei

The crystalline phases and domain configuration in the morphotropic phase boundary composition Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-0.34PbTiO{sub 3} (PMN-0.34PT) single crystal have been investigated by synchrotron-based X-ray 3D Reciprocal Space Mapping (3D-RSM) and Piezoresponse Force Microscopy. The coexistence of tetragonal (T) and monoclinic M{sub C} phases in this PMN-0.34PT single crystal is confirmed. The affiliation of each diffraction spot in the 3D-RSM was identified with the assistance of qualitative simulation. Most importantly, the twinning structure between different domains in such a mixed phase PMN-PT crystal is firmly clarified, and the spatial distribution of different twin domains is demonstrated. In addition, themore » lattice parameters of T and M{sub C} phases in PMN-0.34PT single crystal as well as the tilting angles of crystal lattices caused by the interfacial lattice mismatch are determined.« less

Development of AlN and TiB2 Composites with Nb2O5, Y2O3 and ZrO2 as Sintering Aids

PubMed Central

González, José C.; Rodríguez, Miguel Á.; Figueroa, Ignacio A.; Villafuerte-Castrejón, María-Elena; Díaz, Gerardo C.

2017-01-01

The synthesis of AlN and TiB2 by spark plasma sintering (SPS) and the effect of Nb2O5, Y2O3 and ZrO2 additions on the mechanical properties and densification of the produced composites is reported and discussed. After the SPS process, dense AlN and TiB2 composites with Nb2O5, Y2O3 and ZrO2 were successfully prepared. X-ray diffraction analysis showed that in the AlN composites, the addition of Nb2O5 gives rise to Nb4N3 during sintering. The compound Y3Al5O12 (YAG) was observed as precipitate in the sample with Y2O3. X-ray diffraction analysis of the TiB2 composites showed TiB2 as a single phase in these materials. The maximum Vickers and toughness values were 14.19 ± 1.43 GPa and 27.52 ± 1.75 GPa for the AlN and TiB2 composites, respectively. PMID:28772681