Phase relations and thermal expansion studies in the CeO 2–NdO 1.5 system

Abstract

The synthesis, characterization, bulk and lattice thermal expansion of a series of compounds with general composition Ce 1− x Nd x O 2− x/2 , (0.0 ≤ x ≤ 1.0) are being reported in this manuscript. XRD pattern of each product was refined to know the solid solubility limit and the homogeneity range. The solid solubility limit of NdO 1.5 in CeO 2 lattice, under the conditions of slow cooling from 1400 °C, is represented as Ce 0.50Nd 0.50O 1.75 (i.e., 50 mol.% of NdO 1.5). There was no solubility of CeO 2 into the hexagonal lattice of NdO 1.5. The C-type Nd 3+ rich phases were also observed in this series. The bulk thermal expansion measurements from ambient to 1123 K, as investigated by a dilatometer, revealed that the α l (293–1123 K) values, within the cubic homogeneity range, decrease on increasing the Nd 3+ content. A similar trend was observed for average lattice thermal expansion coefficient, α a (293–1473 K), as investigated by a high temperature XRD. These studies on Ce 1− x Nd x O 2− x/2 , (0.0 ≤ x ≤ 1.0) system can be used to simulate the phase relation and thermal expansion behavior of Pu 1− x Nd x O 2− x/2 , (0.0 ≤ x ≤ 1.0) as CeO 2 is widely used as a surrogate material for PuO 2.