Experimental phase diagram study of the Eu2O3–Gd2O3–ZrO2 system at 1673 K and 1873 K and thermodynamic modeling of the ternary system

Abstract

The phase relationships of Eu2O3 - Gd2O3 – ZrO2 system at 1873 K and 1673 K were investigated. To experimentally determine the phase relationships, the scanning electron microscopy, X-ray diffraction, and electron probe microanalyzer with wavelength dispersive spectrometer were employed. Our findings indicated that there were no ternary compounds. However, the binary pyrochlore phases (Eu2Zr2O7 and Gd2Zr2O7) formed a continuous solid solution, denotated as (Eu2-xGdx)Zr2O7 at 1673 K. Moreover, the solubility of Gd2O3 was observed to reach at least 28.0 mol.% along Eu2Zr2O7 - Gd2O3 composition line at 1873 K. Additionally, a continuous cubic solid solution was formed between C–Gd2O3 and C–Eu2O3 at 1673 K. The obtained experimental data were utilized to optimize the thermodynamic parameters for the Eu2O3 - Gd2O3 – ZrO2 system. Thermodynamic modeling was carried out to reproduce the present phase diagram experimental results and isothermal phase diagrams of this ternary system at 1673 and 1873 K were calculated.