Phase relation studies in the CeO2–Gd2O3–ZrO2 system

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Abstract
The phase relations in the CeO2–Gd2O3–ZrO2 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 Zr1−xGdxO2−x/2, Ce1−xGdxO2−x/2, Ce1−xZrxO2.00, (Zr0.5Ce0.5)1−xGdxO2−x/2, (Ce0.5Gd0.5)1−xZrxO1.75+x/4, (Zr0.5Gd0.5)1−xCexO1.75+x/4, and (Ce0.8Zr0.2)xGd1−xO1.5+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% GdO1.5 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., Gd1−xCexO1.5+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.