New experimental investigations of phase relations in the Yb2O3–Al2O3 and ZrO2–Yb2O3–Al2O3 systems and assessment of thermodynamic parameters

Phase relations were experimentally studied in the Yb2O3–Al2O3 and ZrO2–Yb2O3–Al2O3 systems. Samples were prepared from oxide mixture and by co-precipitation. Phase equilibria were studied in the range 1523–2023 K and investigated by XRD and SEM/EDX. Heat capacity of the Yb3Al5O12 (YbAG) phase was measured between 293 and 1473 K by DSC. Phase transformations and melting relations were investigated by DTA up to 2373 K. The stability range of Yb4Al2O9 (YbAM) phase was determined to be between 1923 and 2186 K. The character of its melting was determined from crystallisation microstructure and DTA as peritectic. The thermodynamic parameters of the Yb2O3–Al2O3 system were derived based on obtained results. Melting relations in the ternary system were studied experimentally. Based on the data obtained a thermodynamic description for the ternary system was derived. The new experimental study of the ZrO2–Yb2O3 system is recommended to get better fit of experimental data in ternary system.