Phase relation and bulk thermal expansion studies in thoria-neodia system

The synthesis, characterization and bulk thermal expansion studies of a series of compounds with the general composition Th1−xNdxO2−x/2 (0 ≤ x ≤ 1) are reported. The 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 ThO2 lattice, under the conditions of slow cooling from 1673 K, is represented as Th0.50Nd0.50O1.75 (i.e., 50 mol.% of NdO1.5). The subsequent compositions were found to be bi-phasic as Nd2O3 peaks started appearing. The bulk thermal expansion measurements from 293 to 1123 K, as investigated by a dilatometer, revealed that the αl value, within the homogeneity range, increases with increasing Nd3+ content.