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. Cohen's 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.