Structural characterization of CuIn2Se3.5, CuIn3Se5 and CuIn5Se8 compounds

Polycrystalline CuIn2Se3.5, CuIn3Se5 and CuIn5Se8 have been synthesized in vacuum under different cooling conditions resulting in different phases. X-ray diffraction and Rietveld refinement of the diagrams have been used to characterize the different structures obtained. The two former compounds were refined using two different types of structure: stannite (S.G.: I42m) and the proposed P-chalcopyrite (S.G.: P42c). The determined bond distances after refinements indicate a higher tetragonal distortion for stannite type structure than P-chalcopyrite structure. These results seem to indicate that the Cu-In-Se structure with these two stoichiometries belongs to the P42c S.G. On the other hand, for the CuIn5Se8 compound a far different XRD diagram was obtained where all the reflections have been assigned to two structures, named gamma-phases. one trigonal (gamma) and one hexagonal (gamma(H)). (C) 2000 Elsevier Science S.A. All rights reserved.