CeO 2–YO 1.5–NdO 1.5 system: An extensive phase relation study

Abstract

The sub-solidus phase relations in the CeO 2–YO 1.5–NdO 1.5 system have been studied. About 45 compositions in the series Ce 1− x (Y 0.70Nd 0.30) x O 2−0.5 x , Y 1− x (Ce 0.50Nd 0.50) x O 1.5+0.25 x and Nd 1− x (Ce 0.55Y 0.45) x O 1.5+0.275 x were prepared and characterized by powder XRD. In the Ce 1− x (Y 0.70Nd 0.30) x O 2−0.5 x series, there was a gradual transformation from the defective F-type cubic lattice to an ordered C-type phase with increasing x, whereas in the Y 1− x (Ce 0.50Nd 0.50) x O 1.5+0.25 x series, the C-type cubic lattice of yttria was retained over the entire range. In the Nd 1− x (Ce 0.55Y 0.45) x O 1.5+0.275 x system, the compositions with NdO 1.5 content greater than 95 mol% showed coexistence of hexagonal, monoclinic and cubic phases. A biphasic region of monoclinic and C-type cubic phases was observed as NdO 1.5 decreases from 90 to 70 mol%. All the compositions below 70 mol% NdO 1.5, were found to be C-type cubic solid solutions. The phase relations are distinctly characterized by an extensive range of cubic solid solutions, stable under the slow-cooled conditions. To the best of our knowledge, this is the first detailed sub-solidus study reported in CeO 2–YO 1.5–NdO 1.5 system.