Structural characterization of CuIn2Se3.5, CuIn3Se5 and CuIn5Se8 compounds

Abstract

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.: I4̄2m) and the proposed P–chalcopyrite (S.G.: P4̄2c). 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 P4̄2c 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 γ-phases, one trigonal (γ) and one hexagonal (γH).