共查询到20条相似文献,搜索用时 0 毫秒
1.
G. A. Verozubova A. Yu. Trofimov E. M. Trukhanov A. V. Kolesnikov A. O. Okunev Yu. F. Ivanov P. R. J. Galtier S. A. Said Hassani 《Crystallography Reports》2010,55(1):65-70
The defect structure of ZnGeP2 crystals grown from a melt by the vertical Bridgman method has been investigated. A deviation of the melt composition from stoichiometric leads to the formation of striations and the inclusions of other phases which are observed as structures (chains) oriented parallel to the growth axis. According to the microanalysis data, the inclusion composition corresponds to a mixture of ZnGeP2, Zn3P2, and Ge. Nanoinclusions of germanium phosphide are detected by transmission electron microscopy. X-ray topography reveals defects of four types. The main defects in the central part of an ingot are related to the composition fluctuations, and the newly formed dislocations are basically single ones. Most dislocations are formed at the crystal periphery. 相似文献
2.
Single crystals of the anionic conductor La2Mo2O9 are grown by crystallization from a nonstoichiometric melt. Their polymorphism and domain structure, as well as the temperature dependences of conductivity and dielectric permittivity, are studied. In the temperature range 750–600°C, the conductivity of these crystals is as high as 10?1–10?2 Ω?1 cm?1. 相似文献
3.
To elucidate the mechanism of nucleation and growth of filamentary crystals on the bipyramid faces of KH2PO4 (KDP) crystals from solution with the addition of Al(NO3)3 · 9H2O, the growth rates and transverse dimensions of the crystals were measured at various supersaturations, temperatures, and impurity concentrations. The dependences obtained can be interpreted with due regard for the competition between the intrinsic and impurity particles in the presence of Cabrera-Vermilyea stoppers. 相似文献
4.
V. L. Manomenova E. B. Rudneva A. É. Voloshin L. V. Soboleva A. B. Vasil’ev B. V. Mchedlishvili 《Crystallography Reports》2005,50(5):877-882
The high-rate growth of nickel sulfate hexahydrate NiSO4 · 6H2O (α-NSH) crystals up to 120 × 120 × 65 mm3 in size is described for the first time. The data on the distribution of related impurities in the {011} and {001} growth sectors of α-NSH crystals grown at different rates are reported. The transmission spectra of both growth sectors of these crystals are obtained. The structural quality and the optical properties of rapidly and slowly grown α-NSH crystals are compared. It is established that the {011} growth sector of crystals grown at rates exceeding 5 mm/day shows the best characteristics for application in UV filters. 相似文献
5.
A. U. Sheleg E. M. Zub A. Ya. Yachkovskii L. F. Kirpichnikova 《Crystallography Reports》2005,50(6):949-953
The unit-cell parameters of [NH2(CH3)2]MnCl3 · 2H2O crystals are determined by X-ray diffraction analysis and the velocities of longitudinal ultrasonic waves in these crystals are measured by the echo-pulse method in the temperature range 100–315 K. The coefficients of thermal expansion along the principal crystallographic axes are derived from the temperature dependences of the unit-cell parameters. The temperature dependences of the characteristics studied reveal kink anomalies at temperatures of ~125, 179, 203, 260, and 303 K. These anomalies are indicative of structural transformations in the [NH2(CH3)2]MnCl3 · 2H2O crystals, which may be related to the dynamics of dimethylammonium cations. 相似文献
6.
N. I. Sorokin 《Crystallography Reports》2016,61(3):466-468
The electrical conductivity of Cs2CuCl4 single crystals, synthesized by crystallization from aqueous solutions in the CsCl–CuCl2–H2O system, has been investigated. The temperature dependence of the electrical conductivity of crystals in a temperature range of 338–584 K exhibits no anomalies. The electrical transfer activation enthalpy is ΔHσ = 0.72 ± 0.05 eV and the conductivity is σ = 3 × 10–4 S/cm at 584 K. The most likely carriers in Cs2CuCl4 are Cs+ cations, which transfer electric charge according to the vacancy mechanism. 相似文献
7.
A. U. Sheleg E. M. Zub A. Ya. Yachkovskii L. F. Kirpichnikova 《Crystallography Reports》2004,49(6):1028-1031
[(CH3)2NH2]5Cd3Cl11 crystals are grown by the method of isothermal evaporation from saturated aqueous solutions containing dimethylamine and cadmium chlorides, [(CH3)2NH2]Cl and CdCl2.5H2O. The crystal grown are studied by the X-ray diffraction method. It is established that the crystals are orthorhombic with the unit-cell parameters at room temperature a = 18.115 ± 0.004 Å, b = 11.432 ± 0.002 Å, and c = 15.821 ± 0.003 Å. The unit-cell parameters a, b, and c of the [(CH3)2NH2]5Cd3Cl11 crystals are measured as functions of temperature in the temperature range 100–320 K. The data obtained were used to determine the thermal expansion coefficients along the main crystallographic axes. The temperature curves of the unit-cell parameters and thermal expansion coefficients showed pronounced anomalies in the vicinity of the temperatures T 1 = 120, T 2 = 150, and T 3 = 180 K corresponding to the phase transitions in the [(CH3)2NH2]5Cd3Cl11 crystals. The crystals are also characterized by a pronounced anisotropy of thermal expansion. 相似文献
8.
A. A. Pugacheva B. A. Maksimov B. V. Mill’ Yu. V. Pisarevskii D. F. Kondakov T. S. Chernaya I. A. Verin V. N. Molchanov V. I. Simonov 《Crystallography Reports》2004,49(1):53-59
The complete X-ray structure determination of Czochralski grown La3Zr0.5Ga5Si0.5O14 single crystals with the Ca3Ga2Ge4O14 structure is performed (sp. gr. P321, a = 8.226(1) Å, c = 5.1374(6) Å, Z = 1, Mo Kα1 radiation, 1920 crystallographically independent reflections, R = 0.0166, Rw = 0.0192). The absolute structure is determined. It is shown that possible transition of some of La atoms (~1.2%) from the 3e to 6g position may give rise to the formation of structural defects. 相似文献
9.
L. I. Ivleva I. S. Voronina L. Yu. Berezovskaya P. A. Lykov V. V. Osiko L. D. Iskhakova 《Crystallography Reports》2008,53(6):1087-1090
The crystallization conditions for obtaining zinc molybdate single crystals by the Czochralski and Kyropoulos methods from a melt have been studied. The growth parameters of large single crystals of optical quality are determined. The physicochemical and spectral-luminescent characteristics of the single crystals are studied. 相似文献
10.
L. F. Kirpichnikova M. Polomska L. Szczesniak B. Hilczer 《Crystallography Reports》2003,48(5):819-822
The characteristics of the changes in the domain structure of Cs3H(SeO4)2 crystals have been studied in a wide temperature range. An anomalous change in the domain structure in the temperature range near the superprotonic phase transition was found. The anomalies in this temperature range were also found by differential scanning calorimetry. The characteristics of the changes in the domain structure in different phases are compared. 相似文献
11.
O. A. Alekseeva I. A. Verin N. I. Sorokina A. E. Krasil’nikova V. I. Voronkova 《Crystallography Reports》2010,55(4):583-590
Precision X-ray diffraction studies of La2 − x
Bi
x
Mo2O9 (x = 0.04, 0.06, and 0.18) single crystals are performed. It is found that in the compounds doped with bismuth, analogously
with the structure of the metastable βms phase of pure La2Mo2O9 (LM), the La, Mo1, and O1 atoms deviate from the threefold axis on which they are located in the high-temperature β phase.
It is shown that bismuth atoms substitute for part of lanthanum atoms and occupy a position at the threefold axis in the neighborhood
of the split lanthanum position. The implantation of bismuth atoms in the LM structure results in the return of a part of
the molybdenum atoms to the position at the threefold axis. The occupancy of this position is equal to the occupancy of the
bismuth atomic position. 相似文献
12.
A complex study of the elemental composition, structure, and superconducting properties of single crystals of layered oxycarbonate
Bi2Sr4Cu2CO3O8 has been performed taking into consideration the growth and postgrowth annealing conditions. 相似文献
13.
I. P. Makarova V. V. Grebenev I. I. Vasil’ev E. V. Dmitricheva V. A. Komornikov V. V. Dolbinina A. S. Mikheikin 《Crystallography Reports》2016,61(1):18-23
Single crystals of Cs4(HSO4)3(H2PO4) are synthesized and studied for the first time. The new compound is found in the course of studies of the phase diagram of the CsHSO4–CsH2PO4–H2O triple system. Data on the atomic crystal structure of single-crystalline and powder specimens, as well as on structural phase transitions, are obtained. 相似文献
14.
The temperature dependence of spontaneous polarization in Li2Ge7O15, a ferroelectric with one polarization axis, is studied in the temperature range from 4.2 K to TC. An unusual character of spontaneous polarization associated with the change of the crystal behavior from the Ising to multipole type is revealed in the vicinity of TC. The low value of spontaneous polarization is explained not by the relation between certain physical quantities, but rather by the interaction of the components of higher order (n > 2) electric moments which, by definition, have rather low values. The Li2Ge7O15 structure is built by macrofragments consisting of two types of mesotetrahedra whose distortion results in the appearance of pseudopolarization of the nonvector type. 相似文献
15.
The effect that uniaxial pressures along the principal crystallophysical directions have on the dispersion and temperature
dependences of the birefringence in incommensurate K2ZnCl4 crystals has been investigated in a wide temperature range. This parameter has been established to be fairly sensitive to
uniaxial pressures. The spectral and temperature dependences of combined piezo-optic coefficients are analyzed. Significant
anomalies of these coefficients are found at the incommensurate-commensurate phase transition. They are due to the change
in the induced birefringence that results from spontaneous polarization and to the significant effect of uniaxial stress on
the soliton structure of the crystal. The contributions that the electrooptic effect, the elasto-optic effect, and the order
parameter make to the spontaneous changes in the piezooptic coefficients are separated. 相似文献
16.
A. I. Dzhabbarov S. K. Orudzhev G. G. Guseinov N. F. Gakhramanov 《Crystallography Reports》2004,49(6):1038-1041
CuFeTe2 single crystals were grown and the temperature dependence of their magnetic susceptibility in the temperature range 1.8–400 K was investigated. It is found that the magnetic susceptibility shows anomalies at temperatures T s = 65 and T N = 125 K. At T > 125 K, the crystal is in the paramagnetic state controlled by Fe2+ and Cu2+ ions with an effective magnetic moment of 1.44 μB. 相似文献
17.
I. E. Zanin K. B. Aleinikova M. Yu. Antipin M. M. Afanas’ev 《Crystallography Reports》2004,49(4):579-584
The refined data on the crystal structure of Zn3P2 (I) provide evidence for a tetrahedral coordination of metal atoms, which is characteristic of covalent structures with sp3-hybridized orbitals. Deformation-electron-density maps for crystal I, which were constructed from high-precision X-ray diffraction data, confirm the predominantly covalent character of bonds in this compound. The deformation-density maps clearly show covalent bridges with their peaks shifted toward electronegative phosphorus atoms. The longer the bond, the larger the shift. The presence of delocalized electrons indicates that the bonding mechanism is partially metallic. 相似文献
18.
The switching processes in calcium barium niobate crystals CaxBa1–x Nb2O6 with x = 0.32 have been investigated. The dielectric hysteresis loops observed in the samples exposed to alternating fields of different frequencies and constant amplitude have been analyzed. It is shown that the loop formation is caused by the sample heating. The sample temperature increases due to the dielectric loss energy release only up to a certain frequency, above which complete switching becomes impossible. 相似文献
19.
Sodium-and silver-ion exchange in single crystals of two polymorphous modifications of the Na3Sc2(PO4)3 compound has been studied. It is established that in the process of ion exchange, the samples undergo phase transitions similar to the well-known temperature transformations observed in these systems. It is shown that the phases with ferroelectric, ionic, and superionic properties may simultaneously coexist in one sample. 相似文献
20.
Bi12SiO20 crystals have been grown for the first time by the low-thermal gradient Czochralski technique in the 〈111〉 and 〈110〉 directions.
The conditions for reproducible crystal growth with a high-quality polyhedral faceted front are found. The systematic features
of shaping Bi12SiO20 and Bi12GeO20 crystals, grown by the low-thermal gradient Czochralski technique, are compared. The defect formation in these crystals is
studied and their optical homogeneity is analyzed by interferometry. 相似文献