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

The phase relationships of Eu 2 O 3 - Gd 2 O 3 - ZrO 2 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 (Eu 2 Zr 2 O 7 and Gd 2 Zr 2 O 7 ) formed a continuous solid solution, denotated as (Eu 2-x Gd x )Zr 2 O 7 at 1673 K. Moreover, the solubility of Gd 2 O 3 was observed to reach at least 28.0 mol.% along Eu 2 Zr 2 O 7 - Gd 2 O 3 composition line at 1873 K. Additionally, a continuous cubic solid solution was formed between C-Gd 2 O 3 and C-Eu 2 O 3 at 1673 K. The obtained experimental data were utilized to optimize the thermodynamic parameters for the Eu 2 O 3 - Gd 2 O 3 - ZrO 2 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.