共查询到20条相似文献,搜索用时 15 毫秒
1.
Aditya M. Vora 《Crystal Research and Technology》2007,42(3):286-289
Indium intercalated MoSe2 single crystals i.e. InxMoSe2 (0 ≤ x ≤ 1) are grown by direct vapour transport technique. These crystals are structurally characterized by X‐ray diffraction, by determining their lattice parameters ‘a’ and ‘c’ and X‐ray density. The Hall effect and thermoelectric power measurements shows that InxMoSe2 (0 ≤ x ≤ 1) are p‐type in nature. The direct and indirect band gap measurements are also undertaken on these semiconducting materials. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The GaAs crystals, grown with three different methods were simultaneously studied by means of photoelastic and X-ray topographic methods. The methods provide complementary information about lattice deformation. The correspondence between interplanar distance changes and photoelastically measured stress values and the connection between cellular structure and high stress values were also found. 相似文献
4.
A. G. Saraf K. B. Saraf P. A. Wani S. U. Bhandari S. V. Bhoraskar 《Crystal Research and Technology》1985,20(7):961-963
A study of surface structures of Prism faces (110) of ammonium tartrate single crystals grown by gel technique is described and illustrated. Vertical striations closly and widely spaced are observed. Isolated as well as densely populated rectangular elongated hillocks are reported and mechanism of the growth of these faces is assessed in the light of observed surface structure. 相似文献
5.
The temperature dependence of the concentration and shape of long dislocation lines in pure, nearly perfect gallium crystals has been measured by X-ray topography in anomalous transmission (Borrmann-topography). The dislocation structure did not change appreciably between temperatures of 22°C and at least 0.1 mK below the melting point Tm = 29.75°C. A few dislocations decreased their length due to tempering at the melting point. Pre-melting effects could not be detected. 相似文献
6.
Dielectric properties of grown single crystals of Na2SbF5 and Na3Sb2F9 have been carried out. The values of the dielectric constant of Na2SbF5 and Na3Sb2F9 are about 24.1 and 14.3, respectively, at temperatures from 30 °C to 250 °C and 225 °C for 100 kHz. 相似文献
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Ferroelectric Lead Nitrogen Phosphate (LNP) single crystals have been synthesized using the controlled reaction between lead nitrate and orthophosphoric acid solutions by slow diffusion process in silicagel medium. The colourless transparent LNP crystals upto 6 × 4 × 3 mm3 in size have been grown at room temperature. The dielectric measurements have been carried out in the temperature range between 300 to 690 K. The effect of applied frequency on the dielectric constants and dielectric losses has been investigated. It has been observed that the mechanism of the dielectric behaviour is different in the lower and higher frequency and temperature ranges. The activation energy of the oscillators has been calculated and found to be 1.125 eV. Attempt has been made to draw some qualitative conclusions, taking in view, the existing theories of various kinds of polarizations and implications. 相似文献
10.
C. C. Desai 《Crystal Research and Technology》1987,22(4):585-590
Single crystals of ammonium hydrogen tartrate AHT NH4HC4H4O6 have been grown employing the controlled reaction between NH4Cl and (CHOHCOOH)2 by slow diffusion process in silica gels. The variation in the microhardness of AHT crystals has been determined using Vicker's microhardness indentor. The effects of annealing and quenching on the mechanical properties of these crystals have been studied. It is observed that: (i) irrespective of the relative orientation of the indentor and the crystal, the median vents initiated at the sharp indentation edges, (ii) the microhardness of the crystals depends on the applied load, (iii) the microhardness of the crystal is independent on the duration of loading, and (iv) maximum plasticity is observed in quenched crystals. The implications of this behaviour are discussed. 相似文献
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The effect of various growth parameters; seed morphology, growth-temperature and pH of the mother solution on the growth of TGS single crystals is studied. The effect of these variables on the crystal morphology and perfection is reported. It is shown that; (i) The crystal quality is much dependent on the seed and the growth temperature and (ii) the pH-control is a simple and an effective method for obtaining TGS crystals of required morphology. 相似文献
12.
G. Joseph A. Santhosh Kumar L. Iype R. Rajesh G. Louis 《Crystal Research and Technology》2009,44(7):759-762
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) 相似文献
13.
The deformation characteristics of KClO4 single crystals have been studied by the methods of static and dynamic indentation on (001) plane. The cracks produced by the dynamic indentation have been interpreted in terms of slip-twin interactions. Also, the load dependence of Vickers microhardness and its anisotropy in this crystal are reported. The observed hardness anisotropy has been used to confirm the indices of the slip system 〈101〉 〈111〉 operative in this crystal at ordinary temperatures. 相似文献
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L. Malicsk L. Pogny A. L. Tth V. Horvth E. Beregi 《Crystal Research and Technology》2009,44(4):425-432
The as‐grown surface and inner structures of undoped and Nd3+‐, Cr3+‐, V3+‐, Ce3+‐, Er3+ and Yb3+ – and (Er3+ + Yb3+) – doped yttrium aluminum borate (YAB) single crystals grown from (K2Mo3O10 + B2O3) flux by spontaneous crystallization or top seeded solution growth (TSSG) technique, were investigated using optical and scanning electron microscopic and analytic chemical methods. Fine and rough growth hillocks of dislocational origin, growth layers, traces of inner planar defects and foreign phase crystalline debris were found and analyzed on the as‐grown faces of crystals. Irregular grains and regular block structures and foreign phase inclusions were observed and studied in the interior of the crystals. The chemical compositions measured by energy dispersive X‐ray spectrometry on perfect and imperfect micro regions are compared with those obtained by flame atomic absorption spectrometry on bulk crystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
S. Krishnan C. Justin Raj S. M. Navis Priya R. Robert S. Dinakaran S. Jerome Das 《Crystal Research and Technology》2008,43(8):845-850
Single crystals of ferroelectric succinic acid (SA) with very high degree of transparency were grown from aqueous solution by slow evaporation technique. Single crystal X‐ray diffraction analysis reveals that the crystal belongs to monoclinic system with the space group P21/c. Some physical parameters have been determined for grown crystal. The optical absorption study reveals the transparency of the crystal in the entire visible region and the cut off wave length was found to be 240 nm. The optical band gap is found to be 3.75 eV. The dependence of extinction coefficient (k) and refractive index (n) on the wavelength have also been reported. The presence of functional groups was determined qualitatively by using Fourier transform infrared spectrum (FTIR) from which force constant has been calculated. The dielectric constant was also studied as a function of frequency at room temperature and electrical conductivity has been calculated from the Cole‐Cole plot. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
16.
Crystals of CsSbF6 belong to the rhombohedral space groupR¯3-C
3i
2
witha=7.904(1)andc=8.261(1) Å,V=446.95 Å3,Z=3,D
c=4.11 gcm–3. The antimony atom is surrounded by six fluorine atoms in a nearly perfect octahedral configuration with Sb-F 1.875(9) Å, while 12 fluorine atoms surround the cesium atom with closest contact 3.116 Å. Polarized Raman spectra of single crystals of CsSbF6 have been obtained, and it is shown that these results can be interpreted in terms of a unimolecular rhombohedral structure. The small distortion from an octahedral arrangement for the SbF
6
–
group is clearly reflected in the spectra. The Raman results are in better agreement with the space groupR¯3m-D
3d
5
than withR¯3-C
3i
2
, but this conclusion must be regarded with caution since the two features in the vibrational spectra of CsSbF6 which can be used to distinguish between the two structures are weak and ill-defined. 相似文献
17.
Oxidation of BaF2 single-crystals as a result of annealing in air in the temperature range 600° to 900 °C leads to mechanical strengthening. The process kinetics was investigated. It is shown that oxidation takes place in the bulk of crystals owing to oxygen diffusion by formation and growth of oxidation centres. These centres are precipitates of a BaO phase which were revealed by chemical etching. 相似文献
18.
C. K. Sumesh K. D. Patel V. M. Pathak R. Srivastav 《Crystal Research and Technology》2011,46(1):61-64
The current voltage characteristics of In / Cu with n‐type MoSe2 Schottky diodes were measured over a wide temperature range 50 < T < 300 K. The interface formed by In and MoSe2 shows ohmic behavior after annealing the contact at 100 °C for 12 h. The ohmic nature was retained at all the measured temperatures. The Cu ‐ nMoSe2 interface formed a Schottky junction diode with a good rectification ratio. The Schottky barrier height and the ideality factor thereby obtained were 0.72 eV and 1.45, respectively, at room temperature. Below room temperature, the barrier height and the ideality factor vary with decreasing temperature. The changes are significant at low temperatures. Barrier height inhomogeneities at the interface cause deviation in the zero‐bias barrier height and the ideality factor at low temperatures, and produce extra current such that I‐V characteristics remain consistent with the thermionic emission mechanism. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
19.
J. Kumar M. Thirumavalavan F. D. Gnanam P. Ramasamy 《Crystal Research and Technology》1987,22(2):189-192
A study has been made to understand the growth history and growth mechanism of flux grown yttrium aluminium garnet (YAG) single crystals. Etching has been done to reveal the growth patterns of flux grown crystals. Optical and scanning electron micrographs are presented. Optical micrographs were taken under polarised light and oblique incident light. The nature and origin of growth hillock is elucidated. 相似文献