Thermodynamic and Structural Properties of CuCrO 2 and CuCr 2 O 4 : Experimental Investigation and Phase Equilibria Modeling of the Cu–Cr–O System

International audienceThis work considers the equilibria between the stable phases of the Cr-Cu-O ternary chemical system, at atmospheric pressure and in a large temperature range that includes the high-temperature liquid phase. Based on a thorough evaluation of literature data, we performed complementary experimental investigations of solid phase properties (especially the mixed oxides), by implementation of spark plasma sintering and microanalysis, high-temperature X-ray diffraction combined with Rietveld analysis, differential thermal analysis and thermogravimetry. We show that neither the spinel CuCr2O4 nor the delafossite CuCrO2 phases exhibit significant cationic non-stoichiometry. We provide an assessment of the thermodynamic functions of the spinel up to 1200 K, taking into account the phase transition. We propose, for the first time, a consistent thermodynamic description of the Cr-Cu-O system based on the Calphad method, allowing the computation of reactions and phase equilibria, including the high-temperature liquid phase described by the Modified Quasichemical Model