COPPER IN IN2S3 - A STUDY BY X-RAY-DIFFRACTION, DIFFUSE REFLECTANCE AND X-RAY ABSORPTION

A study of the In2S3-Cu2S-CuS system has shown the existence of a solid solution range with the In2S3 vacant spinel crystal structure. An X-ray diffraction study has allowed the identification of two redox processes in the formation of solid solutions with CuS, which is a mixed valency copper sulphide, Cu2(I)Cu(II)(S2)2-S2-. At low CuS concentrations all copper(I) is oxidized to copper(II) and the substitution of indium(III) by copper(II) proceeds without sulphur loss. At higher CuS concentrations the redox reaction is restricted to the sulphur atoms and the substitution of indium(III) by copper(I) and copper(II) is accompanied by sulphur losses. The presence of copper in two oxidation states has been confirmed by diffuse reflectance and X-ray absorption at the Cu K edge.