Phase relations, lattice thermal expansion in Ce1−xEuxO2−x/2 and Ce1−xSmxO2−x/2 systems and stabilization of cubic RE2O3 (RE: Eu, Sm)

The phase relations in CeO2–Eu2O3 and CeO2–Sm2O3 systems have been established under slow-cooled conditions from 1400 °C. The two-phase relations differ as the CeO2–Eu2O3 system showed only two monophasic phase fields, namely F-type cubic and C-type cubic, whereas CeO2–Sm2O3 system showed three phase fields namely F-type cubic, C-type cubic and a biphasic field comprising of C-type cubic and monoclinic phase. An interesting observation of this investigation is the stabilization of C-type rare-earth oxide after Ce4+ substitution, which is attributed to decrease in average cationic size on Ce4+ substitution at RE3+ site. The lattice thermal expansion behavior of F-type solid solution and C-type solid solution in CeO2–Eu2O3 system was investigated by high-temperature XRD.