Experimental and thermodynamic assessment of the fluoride-rich region in the Cu-O-F system

A thermodynamic evaluation and optimization of the CALPHAD type of the Cu-O-F system, together with phase diagram measurements, are considered in the present work as the first step towards a complete evaluation of Cu in the multicomponent system Cu-Fe-Ni-Na-Al-Ca-O-F. Differential Scanning Calorimetry experiments were conducted using a closed crucible to identify the phase transitions in the CuF2-Cu and CuF2-Pt pseudo-binary systems in the presence of oxide impurities. The thermograms and the diffractograms, as measured by X-Ray Diffraction, showed that reactions occurred in both systems, where the CuO impurity from the CuF2 reactant led to the formation of Cu2O after three or four runs. All new model parameters of the fluoride-rich region of the Cu-O-F system were optimized based on this study's experimental results. Measured and calculated results are in good agreement and provide a new interpretation of the phase transitions reported in the literature.