Preparation and electrical conductivity of Pb2Ru2O6.5 crystals

Single crystals of Pb₂Ru₂O_6.5 have been grown by flux method from a mixture of lead oxides. The electrical conductivity of the crystals is of a metallic type, major current carriers being holes.     

Electrical conductivity of sulfamic acid single crystals

Single crystals of sulfamic acid have been grown by the method of slow evaporation at constant temperature. DC electrical conductivity was measured in the temperature range 300 ‐ 440 K along a, b and c‐axes. Conductivity measurements show slope change near 330 K and 410 K. The slope change observed around 330 K may be attributed as due to a phase transition which has been well supported by the DSC and DTA measurements. Slope change observed around 410 K is attributed as the onset of the thermal decomcoposition as evidenced by TGA curve. TGA studies show the crystal is very stable up to 440 K. Activation energies for the conduction process are calculated for all measured crystallographic directions. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thin layers deposited from V2O5 gels: I. A conductivity study

The conductivity ? of V₂O₅ layers deposited from gels of various V⁴⁺ content C was measured over a very large temperature range. The observed variations agree with Mott predictions on polaron hopping. Indeed below ≈ 50 K we reached a new conductivity regime with a well-defined activation energy. The fit of the experimental data to the Schnakenberg model was excellent and thus we could determine the polaron energy W_p, the disorder energy W_D and the mean optical phonon frequency v₀. All these values decrease with increasing C. In contrast whatever C the coupling constant γ was ≈ 10. The variation of W_D with C agrees quantitatively with the values calculated by means of Miller and Abrahams' theory and this led us to the conclusion that in those amorphous V₂O₅ layers disorder is mainly a potential disorder related to non-stoichiometry.     

Anisotropy of the ionic conductivity of CsCu2Cl3 single crystals

The conductivity of CsCu₂Cl₃ single crystals (orthorhombic system, sp. gr. Cmcm) has been investigated for different electric-field directions, perpendicular to the crystallographic c axis and along it, in the temperature range 390–530 K. The increase in conductivity with temperature is due to the ion-carrier transport with activation energies E _a = 0.65 and 0.80 eV for the directions perpendicular to and along the crystallographic axis, respectively. The anisotropy of the crystal ionic conductivity is found to be σ_⊥c /σ_∥c ≈ 40 at 435 K. The thermally activated contribution to the conductivity in the CsCu₂Cl₃ structure is determined by the transport of Cu⁺ ions.     

Electrical conductivity and dielectric properties of potassium sulfamate single crystals

Single crystals of potassium sulfamate are grown by the method of slow evaporation at constant temperature. AC electrical conductivity of potassium sulfamate is measured in the temperature range 300–430 K and in the frequency region between 100 Hz and 3 MHz along the a, b and c‐axes. Complex impedance spectroscopy is used to investigate the frequency response of the electrical properties of the potassium sulfamate single crystal. Temperature variation of AC conductivity and dielectric measurements show a slope change around 345 K for both heating and cooling run and this anomaly is attributed as phase transition, which is well supported by the DSC measurements. Value of loss tangent in the temperature region 330–400 K is found to be very low. Activation energies for the conduction process are calculated along the a, b and c‐axes. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation and characterization of Ni-incorporated FeS2 single crystals

Nickel-incorporated FeS₂ single crystals with various Ni compositions of Fe_0.99S₂:Ni_0.01, Fe_0.98S₂:Ni_0.02, Fe_0.96S₂:Ni_0.04, and Fe_0.9S₂:Ni_0.1 were grown by chemical vapor transport (CVT) method using ICl₃ as a transport agent. Physical properties of the Ni-incorporated FeS₂ single crystals were characterized using X-ray diffraction, Raman spectroscopy, electrical conductivity, and photoconductivity (PC) measurements. By means of the analyses of the X-ray diffraction patterns, the whole series of Ni-doped FeS₂ single crystals were determined to be single-phase and isostructural. Raman spectroscopy of the Ni-doped FeS₂ crystals was carried out at room temperature. Raman resonant peaks of the Ni-doped FeS₂ crystals demonstrate an energy red-shift behavior with respect to the increase of the dopant densities. Conductivity measurements show the resistivity of the Ni-doped FeS₂ decreased as the doping concentration of Ni is increased. Nickel is an n-type dopant, which behaves like a donor level existed near the conduction band edge of the synthetic FeS₂. On the other hand, dopant effect of nickel on the synthetic FeS₂ also destroys the photoconductive sensitivity in the photoconductivity measurements.     

Growth of lithium triborate (LiB3O5) single crystals in the Li2O-B2O3-MoO3 system

Solubility curves are plotted and optimal solvents for growing lithium triborate (LiB₃O₅) single crystals are determined. The crystallization range of this compound in the Li₂O-B₂O₃-MoO₃ system is refined. The molybdenum content in the crystals grown is analyzed.     

Ionic conductivity of BaF2 crystals

By fitting theoretically calculated to experimentally found lg σT ÷ 1/T dependencies (σ conductivity) there were obtained: the free formation enthalpy of anti-Frenkel defects g_AF = 1.81 eV − 7.85 kT, and the mobilities v_V and v_i of F⁻ ion vacancies and interstitials: v_VT = 240 exp (−0.59 eV/kT) cm² K/Vs, v_iT = (4080 + 610) exp (−0.79 eV/kT) cm² K/Vs. The free association enthalpies were reestimated for complexes consisting of single foreign cations (Na⁺, K⁺, Y³⁺, La³⁺, Tm³⁺, Yb³⁺) and the corresponding charge-compensating defects. At the melting point of BaF₂ at least 5.7 per cent of the F⁻ ions are disordered.     

Growth and characterization of 2-amino-5-chlorobenzophenone (2A-5CB) single crystals

Organic nonlinear optical single crystals of 2-amino-5-chlorobenzophenone (2A-5CB) were grown in ethanol by slow solvent evaporation technique. The grown crystals were characterized by single-crystal XRD, FTIR, FT-Raman and UV–vis–NIR techniques. The UV–vis–NIR spectrum ascertains the cut-off wavelength of the sample as 390 nm. The powder second harmonic generation (SHG) technique reveals that 2A-5CB crystal has its SHG efficiency nearly three times that of KDP. The dielectric response of the sample was studied in the frequency region of 50 Hz–1 MHz at varying temperatures. The photoconductivity studies indicate that the 2A-5CB crystal exhibits negative photoconductivity. TGA–DTA studies confirm the melting point of the sample as 101.5 °C.     

V2O5/g-C3N4复合物的制备及可见光催化性能研究

以偏钒酸铵和尿素混合物为前驱体,混合煅烧制备了V2O5/g-C3N4复合物催化剂.用X射线衍射(XRD)、傅里叶红外光谱(FT-IR)、扫描电镜(SEM)、透射电镜(TEM)、紫外-可见光漫反射吸收光谱(UV-vis)、比表面积测试(BET)、光致发光谱(PL)等对其结构进行了表征.结果表明复合物中存在V2O5和g-C3N4形成异质结构,其禁带宽度减小、吸收带边红移,光催化效率有显著提高.以亚甲基蓝(MB)为目标化合物,评价了样品的光催化活性,当前躯体中尿素与NH4VO3质量比为10∶1,煅烧温度为500℃,煅烧时间为0.5h,催化剂活性最高.在60W日光灯照射40 min,对亚甲基蓝得降解率达到97.52;.     

Preparation of Cu2ZnSnS4 single crystals from Sn solutions

We investigated the phase diagrams of the Cu₂ZnSnS₄ (CZTS)–Sn pseudobinary system in order to obtain knowledge useful for the growth of high-quality CZTS single crystals using a solution-based method. For Sn solutions saturated with less than ～60 mol% CZTS, the solutes are separated into two phases (CZTS phase+SnS_x phase+liquid phase). On the other hand, for solutions with more than 60 mol% CZTS, the solutes are single phase (CZTS phase+liquid phase). The CZTS single crystals were obtained from a 70 mol% CZTS solution (liquid temperature 850 °C) at 900 °C. The powder X-ray diffraction (XRD) pattern of the CZTS single crystal shows preferred orientations of (112), (220) and (312) planes, confirming the Kesterite structure of CZTS. The Raman spectrum shows three peaks at 287, 338, 371 cm^?1, which corresponded to CZTS peaks. The composition of the CZTS single crystal along the growth direction is found to be slightly Cu-poor, Zn-rich and S-rich. Therefore, it is assumed that the Cu vacancy is the dominant p-type conduction mechanism.     

Preparation and properties of ultratransparent NaCl single crystals

The preparation of up to 100 mm diameter single crystalline ingots of ultratransparent NaCl by injecting the reactive atmosphere is reported. The resulting material exhibits high optical quality and bulk absorption coefficient at 10.6 μm of 0.91 × 10⁻³ cm⁻¹, close to the intrinsic value, which makes it suitable for transmissive components in high-power CO₂ lasers.     

Investigations Concerning the Quasi-binary System V2O5 – Nb2O5

In examining the pseudobinary system V₂O₅ – Nb₂O₅ it was possible to isolate, by systematic transport reactions, just one stable compound of the mean composition V_1.057Nb_8.943O₂₅ in addition to the boundary phases, which is in contrast to the data given in the literature. The phase width of this compound is very small and within the confidence limits of the analytical method of determination of 0.2 p.c. A maximum of 50 ppm Nb₂O₅ only dissolve in V₂O₅. Determining the solubility of V₂O₅ in Nb₂O₅ failed, because the two-phase products resulting during the chemical transport of the respective samples could not be separated exactly.     

Optical inhomogeneities in Li2B4O7 single crystals

Lithium tetraborate, Li₂B₄O₇ (LTB) crystals were grown by Czochralski technique. It belongs to tetragonal system with lattice parameter a = b = 9.479 Å, c = 10.286 Å. Transmission range of this crystal is 170 nm – 3300 nm. This material has attracted much attention because of its application in higher harmonic generation of Nd:YAG laser and radiation dosimetry. The grown crystals were characterized for their optical inhomogeneity using etch pit study, hardness, conoscopy, interferometry, and UV‐VIS transmittance techniques. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A novel growth method for ZnAl2O4 single crystals

ZnAl₂O₄ is a well‐known wide band gap compound semiconductor (E_g=3.8eV), ceramic, opto‐mechanical, anti‐thermal coating in aero‐space vehicles and UV optoelectronic devices. A novel method for the growth of single crystals of a ternary oxide material was developed as a fruit of a long term work. Material to be grown as metal incorporated single crystal was taken as precursor and put into a bath containing acid as reaction speed up reagent (catalyst) as well as solvent with a metal foil as cation scavenger. Using this method, ZnAl₂O₄ crystals having hexagonal facets are prepared from a single optimized bath. Structural and compositional properties of crystals were studied using Philips, Xpert ‐ MPD: X‐ray diffractometer and Philips, ESEM‐TMP + EDAX. Thus technique was found to be a new low cost and advantageous method for growth of single crystals of ternary oxide a material. We hope that these data be helpful either as a scientific or technical basis in material processing. Dedicated to Prof. P. Ramasamy © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Growth and properties of Lu3Al5O12-RE3+ single crystals

Optically transparent garnet single crystals were grown from Lu₃Al₅O₁₂ melts containing different RE³⁺ ions. The distribution coefficient of Nd³⁺ ions is found to be a function of the growth rate. Lu₂O₃–Al₂O₃ system studies have been partially carried out. Measurements of the lattice data, absorption spectra and comparison with some properties of Y₃Al₅O₁₂ single crystals have also been made.     

DC conductivity studies in K3Na(SeO4)2 single crystals

DC electrical conductivity studies were carried out along the three crystallographic axes for Tripotassium sodium diselenate (K₃Na(SeO₄)₂ or KNSe). Earlier studies of phase transition in this crystal show successive phase transitions at 334 K, 346 K, 730 K, and 758 K. In this paper we report the dc electrical conductivity measurements in the temperature region 303 K – 430 K along a, b and c – axes. An anomaly in conductivity was obtained around 341 K and another one around 333 K. These can be attributed as due to phase transitions in this crystal. A strong anomaly also has been observed along the c‐axis and comparatively week one along a and b axes around 395 K for the first time. This can be due to newly observed phase transition in the crystal. DSC taken for the sample also shows endothermic peak supporting the occurrence of newly observed phase transition. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)