Phase relation studies in the CeO 2–Gd 2O 3–ZrO 2 system

Abstract

The phase relations in the CeO 2–Gd 2O 3–ZrO 2 system have been established after slowly cooling the samples from 1400 °C. Ceria has been used as a surrogate material in place of plutonia. About 80 compositions in Zr 1− x Gd x O 2− x /2, Ce 1− x Gd x O 2− x /2, Ce 1− x Zr x O 2.00, (Zr 0.5Ce 0.5) 1− x Gd x O 2− x /2, (Ce 0.5Gd 0.5) 1− x Zr x O 1.75+ x /4, (Zr 0.5Gd 0.5) 1− x Ce x O 1.75+ x /4, and (Ce 0.8Zr 0.2) x Gd 1− x O 1.5+ x / 2 were prepared by a three steps heating protocol. Based on the refinement of the XRD data, several phase regions namely; cubic fluorite type solid solution, C-type solid solution, and various biphasic regions could be delineated. This system showed the existence of a very wide cubic phase field. About 17.5 mol% GdO 1.5 was found to fully stabilize the cubic zirconia. On the other hand ceria did not stabilize the cubic zirconia. The anion-excess gadolinia, i.e., Gd 1− x Ce x O 1.5+ x was found to retain the C-type lattite unlike pure gadolinia. The ternary phase relations were mainly characterized by the presence of wide homogeneity ranges of fluorite type or C-type phases.