Phase diagram calculations of ZrO2-based ceramics with an emphasis on the reduction/oxidation equilibria of cerium ions in the ZrO2-YO1.5-CeO2-CeO1.5system

Phase diagram calculations that were made previously for the ZrO2-MOm/2(m = 2, 3, 4) systems and for the ZrO2-YO1.5-MOm/2 (M = transition metals) syst ems have been extended to the ZrO2-YO1.5-CeO2(-CeO1.5) system to make an at tempt to explain (1) thermogravimetric (TG) results as a function of oxygen potential, (2) electronic conductivity as a function of oxygen potential, and (3) a miscibility gap observed in air. The interaction parameters for t he CeO2-CeO1.5-YO1.5 system were obtained from the reported oxygen nonstoic hiometry in CeO2-x and rare earth doped ceria, (Ce,RE)O2-delta. The interac tion parameters for the ZrO2-CeO2 subsystem were obtained so as to reproduc e the observed miscibility gap at 1273 K, Those thermodynamic properties ca n reproduce consistently the experimental behaviors of the electronic condu ctivity and the TG results in the (Zr1-xCex)(0.8)Y0.2O1.9 solid solutions; these indicate the enhancement of reduction of CeO2.