Investigation of structural anomaly and metal ordering in the solid solution 2ZnS–CuInS2 by neutron diffraction

Abstract Powder samples of Zn 2 x (CuIn) 1 −x S 2 were synthesized by solid state reaction ( T =950°C) in sealed evacuated silica tubes. Based on neutron- and X-ray diffraction data structural parameters were determined using the Rietveld method. Samples with 0.4⩽ x ⩽1 crystallize in the cubic sphalerite-type structure, samples with 0.1⩾ x ⩾0 crystallize in the tetragonal chalcopyrite-type structure. A miscibility gap was found in the region 0.1 x I B III C 2 VI chalcopyrites relative to the binary AC zinc-blende analogon was considered in dependence on the chemical composition of the mixed crystals. This work extends the ‘conservation of tetrahedral bonds’ model to quarternary mixed crystals by modifying the equations for the ternary chalcopyrite compounds to incorporate the 2Zn↔(Cu,In) substitution as well as different types of cation ordering. A non-statistic Zn distribution on the cation sites of the chalcopyrite structure accompanied by Cu–In anti site occupation was deduced from the experimental determined anion parameter and metal site occupancies from the Rietfeld refinement of the neutron-diffraction data.