Structural and thermal properties of Cu1-xAgxInS2 chalcopyrite solid solutions

The anisotropic thermal expansion of Cu1-xAgxInS2 chalcopyrite solid soluti ons was studied by x-ray diffraction from 80 to 650 K. Over the entire temp erature range studied, the thermal expansion of the solid solutions was fou nd to be anisotropic: the c-axis thermal expansion is considerably smaller than the a-axis thermal expansion. The solid solutions with 0.55 < x < 1.0 exhibit negative c-axis thermal expansion. The composition dependences of t he thermal expansion coefficients and anisotropy parameters are nonlinear. The anisotropy parameters rise monotonically with increasing x. The correla tion between the thermal expansion anisotropy and tetragonal distortion del ta = 2 - c/a is considered. Directions of zero thermal expansion are identi fied.