ZrO2-NdO1.5 system: Investigations of phase relation and thermophysical properties

Abstract

Exploring the structural and thermophysical behaviour of Nd-Substituted ZrO2 is vital in context of matrices for minor actinide transmutation. Hence, phase relations have been studied in this system using high temperature sintered samples prepared by gel combustion route. Phase characterization of Zr1−xNdxO2−x/2 (0.0≤x≤1.0) series was carried out using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). With increasing NdO1.5 content, the system evolved in the sequence of (a) monoclinic zirconia (b) mixture of monoclinic+cubic stabilized zirconia, (c) cubic stabilized zirconia (d) mixture of stabilized zirconia+pyrochlore (e) pyrochlore (f) mixture of pyrochlore+hexagonal Nd2O3 and (g) pure hexagonal Nd2O3. Lattice and bulk thermal expansion of few selected compositions were characterized by high temperature XRD (298–1273K) and dilatometry (323–1673K). Average coefficient of thermal expansion decreased with increasing NdO1.5 fraction in Zr1−xNdxO2−x/2 series (x=0.2, 0.3, 0.4, 0.5) solid solutions, which has been attributed to increasing order in cation sub-lattice resulting in overall increase in lattice stability. Thermal conductivity has been reported for a representative composition Zr0.8Nd0.2O1.90.