X-ray diffractometry of AlGaAs/GaAs superlattices and GaAs in the temperature range 5–295 K

1989 ◽  
Vol 22 (4) ◽  
pp. 372-375 ◽  
Author(s):  
G. Clec'h ◽  
G. Calvarin ◽  
P. Auvray ◽  
M. Baudet
Keyword(s):  
Thermal Expansion ◽  
Temperature Dependence ◽  
Low Temperatures ◽  
X Ray ◽  
Lattice Constants ◽  
Temperature Range ◽  
Thermal Expansion Coefficients ◽  
Gaas Substrates ◽  
Expansion Coefficients ◽  
Tetrahedrally Bonded

The temperature dependence of the lattice constants of Al x Ga1 − x As/GaAs superlattices MBE-grown on (001) oriented GaAs substrates was determined by X-ray diffractometry. The thermal expansion coefficients of these materials become negative at low temperatures, like that of GaAs and other tetrahedrally bonded covalent solids. The temperature dependence of the stress in these structures was also studied; although its value increases as temperature decreases, strain remains elastic down to 5 K.

Temperature dependence of lattice constants of the rare-earth hexaborides EuB6and GdB6

2001 ◽  
Vol 34 (2) ◽  
pp. 208-209 ◽  
Author(s):  
Yasuhiko Takahashi ◽  
Masayoshi Fujimoto ◽  
Masashi Tsuchiko ◽  
Ken-Ichi Ohshima
Keyword(s):  
Rare Earth ◽  
Temperature Dependence ◽  
Linear Thermal Expansion ◽  
X Ray ◽  
Lattice Constants ◽  
Thermal Expansion Coefficients ◽  
Temperature Dependences ◽  
Expansion Coefficients ◽  
Ray Patterns ◽  
The Rare Earth

The temperature dependences of the lattice constants of single crystals of the rare-earth hexaborides EuB6and GdB6were determined by analysing the low-temperature X-ray patterns. The lattice constant decreases monotonously with decreasing temperature. The linear thermal expansion coefficients for the two compounds were also obtained by analysing the temperature dependence of the lattice constants.

Crystal structure and thermal expansion of hexakis(phenylthio)benzene and its CBr4 clathrate

1995 ◽  
Vol 73 (4) ◽  
pp. 513-521 ◽  
Author(s):  
Darek Michalski ◽  
Mary Anne White ◽  
Pradip K. Bakshi ◽  
T. Stanley Cameron ◽  
Ian Swainson
Keyword(s):  
Crystal Structure ◽  
Thermal Expansion ◽  
Neutron Powder Diffraction ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
Space Group ◽  
X Ray ◽  
Temperature Range ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

The crystal structures of hexakis(phenylthio)benzene (HPTB) and its CBr4 clathrate have been determined by single crystal X-ray diffraction data collected at T = 18 °C and refined to final Rw of 0.036 and 0.047, respectively. Pure HPTB is triclinic, space group [Formula: see text] (No. 2), with a = 9.589(2) Å, b = 10.256(1) Å, c = 10.645(2) Å, α = 68.42(1)°, β = 76.92(2)°, γ = 65.52(1)°, and Z = 1. The CBr4 clathrate of HPTB is rhombohedral, space group [Formula: see text] (No. 148), with a = 14.327(4) Å, b = 20.666(8) Å, and Z = 3. The host–guest mole ratio of HPTB–CBr4 is 1:2. Neutron powder diffraction was carried out on powders of both compounds in the temperature range 25 K < T < 295 K. Thermal expansion coefficients were determined for HPTB and HPTB–CBr4 over this temperature range. Keywords: thermal expansion, crystal structure, clathrate.

scholarly journals Studies on Thermophysical Properties of CaO and MgO by γ-Ray Attenuation

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
A. S. Madhusudhan Rao ◽  
K. Narender
Keyword(s):  
Thermal Expansion ◽  
Temperature Dependence ◽  
Thermophysical Properties ◽  
Linear Thermal Expansion ◽  
Temperature Dependent ◽  
Degree Polynomial ◽  
Attenuation Coefficients ◽  
Temperature Range ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

The study on temperature dependent γ-ray attenuation and thermophysical properties of CaO and MgO has been carried out in the temperature range 300 K–1250 K using different energies of γ-beam, namely, Am (0.0595 MeV), Cs (0.66 MeV), and Co (1.173 MeV and 1.332 MeV) on γ-ray densitometer fabricated in our laboratory. The linear attenuation coefficients (μl) for the pellets of CaO and MgO as a function of temperature have been determined using γ-beam of different energies. The coefficients of temperature dependence of density have been reported. The variation of density and linear thermal expansion of CaO and MgO in the temperature range of 300 K–1250 K has been studied and compared with the results available in the literature. The temperature dependence of linear attenuation coefficients, density, and thermal expansion has been represented by second degree polynomial. Volume thermal expansion coefficients have been reported.

THERMAL EXPANSION OF SINGLE CRYSTALS OF ZINC AT LOW TEMPERATURES

1965 ◽  
Vol 43 (7) ◽  
pp. 1328-1333 ◽  
Author(s):  
D. A. Channing ◽  
S. Weintroub
Keyword(s):  
Experimental Data ◽  
Thermal Expansion ◽  
Single Crystals ◽  
Low Temperatures ◽  
Linear Thermal Expansion ◽  
Optical Interference ◽  
Temperature Range ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
Good Agreement

The linear thermal expansion coefficients αψ of two single crystals of Zn of orientations ψ = 10.8° and 63.9 ° with the hexad axis were measured over the temperature range of about 20–270 °K using an absolute Fizeau optical interference technique. The two principal coefficients, [Formula: see text] and [Formula: see text], corresponding to ψ = 0° and 90 ° respectively, were calculated from the Voigt relation, and their values are compared with previously reported experimental data. Above 60 °K there is good agreement with previous work, and below 60 °K the results confirm, in general, the data obtained by McCammon and White. The Grüneisen parameter γ is essentially constant at about 2.1 in the range 100–270 °K, but below 100 °K γ rises appreciably with decreasing temperature and reaches the value of about 3.5 at 20 °K.

Thermal Stability of the Structural and Electronic Properties of Strain Symmetrized Sim Gen Superlattices and Ungraded, Nearly Relaxed Si1−x Gex

1992 ◽  
Vol 281 ◽  
Author(s):  
P. A. Dafesh ◽  
P. M. Adams ◽  
V. Arbet-Engels ◽  
K. L. Wang
Keyword(s):  
Thermal Expansion ◽  
Energy Shift ◽  
Buffer Layers ◽  
X Ray ◽  
Lattice Constants ◽  
Thermal Expansion Coefficients ◽  
Structural And Electronic Properties ◽  
Expansion Coefficients ◽  
The Difference ◽  
Anneal Temperature

ABSTRACTIn this study, photoreflectance (PR) spectroscopy and x-ray rocking curves measurements were used to study the variation in strain configuration, defect propagation, structural properties and direct electronic transition energies in Sim Gen superlattices (SL) and nearly relaxed Si1−x Gex buffer layers grown on < 100 > Si as a function of annealing temperature. The in-plane (a│) and perpendicular (a┴) lattice constants of the alloy buffer layers are found to vary only slightly with anneal temperature, TA, up to a temperature To. For TA To, the in-plane strain changed from roughly zero a│ ≈ a┴ (relaxed) or a┴ > a│ (compressive) to a┴ > a│ (tensile). This change in strain configuration is believed to be caused by the difference in thermal expansion coefficients between the epilayer and the Si substrate. The anneal temperature T0 is also correlated with the disappearance of higher order x-ray harmonics from the SL. This point was also correlated with a large energy shift and broadening of the PR spectra from the SL. The shift in energy of the PR spectra is explained in terms of the interdiffusion of Si and Ge at SL heterointerfaces, and to a lesser degree, the strain induced by the above mentioned difference in thermal expansion coefficients. The PR spectra of the alloy E0 transitions are also observed to shift to higher energy with increasing TA.

The influence of the sapphire substrate on the temperature dependence of the GaN bandgap

1999 ◽  
Vol 572 ◽  
Author(s):  
Joachim Krüiger ◽  
Noad Shapiro ◽  
Sudhir Subramanya ◽  
Yihwan Kim ◽  
Henrik Siegle ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Temperature Dependence ◽  
Sapphire Substrate ◽  
Measured Temperature ◽  
Temperature Range ◽  
Thermal Expansion Coefficients ◽  
Small Influence ◽  
Expansion Coefficients ◽  
The Difference ◽  
First Time

ABSTRACTThis paper analyses the influence of the sapphire substrate on stress in GaN epilayers in the temperature range between 4K and 600K. Removal of the substrate by a laser assisted liftoff technique allows, for the first time, to distinguish between stress and other material specific temperature dependencies. In contrast to the prevailing assumption in the literature, that the difference in the thermal expansion coefficients is the main cause for stress it is found that the substrate has a rather small influence in the examined temperature range. The measured temperature dependence of stress is in contradiction to the published values for the thermal expansion coefficients for sapphire and GaN.

The crystal structure and thermal expansion of the CCl4 adduct of Dianin's compound

1990 ◽  
Vol 68 (8) ◽  
pp. 1352-1356 ◽  
Author(s):  
Walter Abriel ◽  
André Du Bois ◽  
Marek Zakrzewski ◽  
Mary Anne White
Keyword(s):  
Crystal Structure ◽  
Thermal Expansion ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients ◽  
Dianin's Compound

The crystal structure of the title compound has been determined by single crystal X-ray diffraction data collected at 293 K, and refined to a final Rw of 0.057. The crystals are rhombohedral, space group [Formula: see text], with a = 27.134(8) Å, c = 10.933(2) Å, and Z = 18. The mole ratio of Dianin's compound (4-p-hydroxyphenyl-2,2,4-trimethylchroman) to CCl4 is 6:1. The guest molecules are disordered. X-ray powder diffraction was carried out in the temperature range from 10 to 300 K. From this, the thermal expansion coefficients for the a- and c-axes and the volume have been determined. Keywords: thermal expansion, crystal structure, clathrate.

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