THERMAL EXPANSION OF COPPER GALLIUM SELENIDE AT HIGH TEMPERATURES.

Data on the tetragonal unit cell parameters a and c of polycrystalline copper gallium selenide obtained between 301-958 K by x-ray powder diffractometry are used to evaluate the linear thermal expansivities alpha // PERPEND and alpha // parallel (perpendicular and parallel to the principal axis, at various temperatures. The mean values of alpha // PERPEND and alpha // parallel are found to be 12. 82 multiplied by 10** minus **6 K** minus **1 and 4. 18 multiplied by 10** minus **6 K** minus **1 respectively, and the axial ratio, c/a, changes with a coefficient of minus 8. 58 multiplied by 10** minus **6 K** minus **1. This result indicates an increase in tetragonal distortion, 2-c/a, with temperature. An attempt is made to explain the increase in tetragonal distortion with temperature and the anisotropic thermal expansion of CuGaSe//2 in terms of the thermal expansion of the Cu-Se and Ga-Se bonds; both covalent and ionic binding forces of the lattice are accounted for. Refs.