X-ray study of CuGa x In1−x Se2 solid solutions

The semiconducting compound CuGa x In1 − x Se2 crystallizes in the chalcopyrite structure (space group I{ 4}2d, Z = 4). The X-ray powder data for x = 1, 0.75, 0.6, 0.5, 0.4, 0.25 and 0.0 have been collected and it is found that the lattice parameters a and c and their ratio c/a vary linearly with x. Thus the composition of any chalcopyrite in the pseudo-binary system CuGaSe2 and CuInSe2 can be obtained from the accurate lattice parameters. The crystallite size determined from the (112) plane is minimum for x = 0.50 (~ 1000 Å) and away from x = 0.50 it increases. A value of u = 0.240 (5) has been established for fixing the Se-atom positions in the CuGa0.5In0.5Se2 solid solution. The JCPDS Diffraction File No. for CuInSe2 is 40-1487 and for CuGa0.5In0.5Se2 is 40-1488.