Phase relations in the ZrO2–Nd2O3–Y2O3 system: experimental study and CALPHAD assessment

Abstract

Abstract The thermodynamic parameters of the Nd2O3–Y2O3 system were re-assessed for better reproduction of experimental data. The thermodynamic parameters were combined from binary descriptions to calculate phase diagrams for the ternary system ZrO2–Nd2O3–Y2O3. The calculated phase diagrams were used to select compositions for the experimental studies at 1 250, 1400 and 1 600°C. The samples were synthesised by co-precipitation and heat treated at 1 250–1 600 °C, investigated by X-ray diffraction and scanning electron microscopy combined with energy dispersive Xray spectroscopy. It was found that solubility of the Y2O3 in the pyrochlore phase exceeds 10 mol.%. The experimental data obtained for phase equilibra were used to derive thermodynamic parameters for fluorite, Y2O3 cubic phase C, monoclinic B and Nd2O3 hexagonal A phases by CALPHAD method. The isothermal sections and liquidus surface were calculated for the ZrO2–Nd2O3–Y2O3 system.