Phase equilibria in the Co–Cu–O–Si system

The thermodynamic description of liquid and fcc phase in the Co–O system is obtained using available experimental data on oxygen dissolution in solid and liquid cobalt. Thermodynamic properties of the liquid are determined in the system cobalt oxide – copper oxide using two contradictory experimental data sets from the literature. Depending on the value of the mixing parameters of the liquid phase two different sets of parameters consistent with the phase relations mentioned above are obtained. ing the data on the ternary systems a thermodynamic description of the solid phases in the Co–Cu–O–Si system is obtained. The mixing parameters for olivine and the Gibbs energy of fictive Cu2SiO4 end-member are optimised using the experimental data obtained in this study on the Co/Cu partitioning between olivine and the (Co, Cu)O phase with halite structure. It is found that several parameter sets equally well describing experimental results are possible. A knowledge of Co/Cu partitioning between olivine and the (Cu, Co)O phase with structure of CuO in equilibrium with SiO2 is crucial to constrain thermodynamic parameters for olivine.