A copper-deficient tetragonal phase derived from chalcopyrite CuGaS2

Abstract

Direct synthesis of CuGaS2 from elemental ingredients in a two-zone furnace resulted in a macroseparation of Cu-rich and Ga-rich regions over the crystallization volume. In the Cu-rich parts of the ingot, a near-stoichiometric CuGaS2 chalcopyrite phase. (I (4) over bar 2d) and copper sulfides were found. In the Ga-rich part, along with a chalcopyrite phase with some Cu deficiency, a new tetragonal phase I (4) over bar m2 with composition close to Cu5Ga9S16 and the crystal lattice parameters a = 3.7777(2) angstrom, c = 5.2483(4) angstrom was revealed. It was concluded that this Cu-deficient chalcopyrite-like phase is not an ordered defect compound (ODC). As opposed to the systems Cu-Ga-Se and Cu-Ga-Te, in a system based on sulfur, the ODC phenomenon is unlikely to occur.