Phase relations and thermal expansion studies in the CeO2-NdO1.5 system

The synthesis, characterization, bulk and lattice thermal expansion of a series of compounds with general composition Ce1−xNdxO2−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 NdO1.5 in CeO2 lattice, under the conditions of slow cooling from 1400 °C, is represented as Ce0.50Nd0.50O1.75 (i.e., 50 mol.% of NdO1.5). There was no solubility of CeO2 into the hexagonal lattice of NdO1.5. The C-type Nd3+ 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 αl (293-1123 K) values, within the cubic homogeneity range, decrease on increasing the Nd3+ content. A similar trend was observed for average lattice thermal expansion coefficient, αa (293-1473 K), as investigated by a high temperature XRD. These studies on Ce1−xNdxO2−x/2, (0.0 ≤ x ≤ 1.0) system can be used to simulate the phase relation and thermal expansion behavior of Pu1−xNdxO2−x/2, (0.0 ≤ x ≤ 1.0) as CeO2 is widely used as a surrogate material for PuO2.