K. Sathyanarayana Murthy

Thermal expansion anomaly in silver indium selenide at elevated temperatures

Abstract A precise determination of the lattice parameters of silver indium selenide was made in the temperature range 28–478 °C using a 19 cm Unicam high temperature powder camera and Cu Kα radiation. Cohens least-squares method was adopted for determining the lattice parameters at each temperature. The data were used to evaluate the coefficients of thermal expansion, perpendicular ( α ⊥ and parallel ( α ∥ ) to the principal axis, at various temperatures. The parameter a decreases non-linearly with increasing temperature whilst the parameter c increases from room temperature to about 360 °C and then decreases non-linearly. The unit cell volume decreases non-linearly with temperature throughout the temperature range studied. The negative value of α ⊥ increases linearly with increasing temperature; the positive value of α ∥ decreases non-linearly, becomes zero at about 360 °C and above 360 °C it becomes negative and increases numerically with increasing temperature.

X-ray studies on the thermal expansion of copper indium disulphide

The lattice parameters of the compound copper indium disulphide (CuInS2) have been measured by x-ray diffraction. The data have been used to evaluate the coefficients of thermal expansion, perpendicular and parallel to the principal axis. The thermal expansion studies revealed the anisotropy between the axial expansion coefficients having a larger coefficient of expansion alonga axis than that alongc axis. The anisotropic thermal expansion of this compound is interpreted in terms of the thermal expansion of the Cu-S and In-S bonds.

Anisotropic thermal expansion of copper gallium selenide

Unit-cell parameters for the chalcopyrite type ternary semiconducting compound copper gallium selenide (CuGaSe2) have been determined accurately, using the least-squares method, for reflections in the range of Bragg angles 64-82 degrees , by the X-ray powder diffraction method. A study of the thermal expansion of the chalcopyrite structure unit-cell of the compound, determined over the temperature range 28-685 degrees C, has revealed the anisotropy between the axial expansion coefficients; that for the c axis (24.93*10-6 degrees C-1) is about four times that for the a axis (5.91*10-6 degrees C-1) at 50 degrees C. Anomalous behaviour of the expansion coefficients, similar to that for AgInSe2, AgGaSe2 and AgGaS2, has not been observed for this compound.

Pressure-induced structural transformation in potassium stanichloride

Pressure-induced structural transformation in potassium stanichloride has been studied by x-ray diffraction at room temperature. The change in the diffraction pattern started at about a pressure of 15 kbar and continued upto 50 kbar. The pattern recorded at about 50 kbar could be indexed basing on an orthorhombic lattice, with lattice parametersa=7.32,b=7.02 andc=8.02 Å.