Phase equilibria in the La2O3-Sm2O3-ZrO2 system: Experimental studies and thermodynamic modeling

Abstract

A series of ceramic samples were prepared to experimentally investigate sub-solidus phase relations in the La2O3-Sm2O3-ZrO2 system at 1873 K and 1673 K. No ternary compounds have been observed, while the binary La2Zr2O7 and Sm2Zr2O7 pyrochlore phases form a continuous solid solution La2−xSmxZr2O7 in the ternary system at the selected temperatures. X-ray diffraction and microstructure results demonstrated that the pyrochlore phase is stable in the ZrO2-rich corner. The homogeneity range of the pyrochlore phase was carefully determined and the phase boundary of the cubic ZrO2 (fluorite phase) which extends into the ternary system was also constructed via electron probe microanalysis. The as-obtained data were adopted to determine the mixing parameters for the pyrochlore and fluorite phases in the present thermodynamic modeling. A self-consistent database of the La2O3-Sm2O3-ZrO2 system was accordingly established for the first time and the calculations agree well with the experimental data in the current work.