Challenges and structural characterization of the solid solution Cu2Zn(GexSi1-x)Se4.

The quaternary chalcogenides Cu 2 ZnSiSe 4 and Cu 2 ZnGeSe 4 crystallize in the orthorhombic wurtz-stannite and tetragonal kesterite type structures, respectively. To investigate thestructural transformation within the solid solution series Cu 2 Zn(Ge x Si 1-x ) Se 4 a systematic structural study was performed. Polycrystalline samples, prepared by solid state reaction, show a single quaternary phase as analyzed by WDX spectroscopy. Structural parameters of the mixed crystals were obtained using powder X-ray diffraction. It can be shown that apart from Cu 2 ZnSiSe 4 , Si-rich mixed crystals of this series adopt the wurtzstannite type structure. The lattice parameters are in consistency with Vegard's law and increase with increasing Ge content