[en] Highlights: • Existence of multi-phasic phase field across the composition range as shown by XRD • Evolution of defect fluorite to pyrochlore structure upon increasing Nd³⁺-content • Ordered pyrochlore micro-domains in bulk defect fluorite lattice revealed by Raman spectroscopy. • Lattice and bulk thermal expansion coefficient decreased with Nd^{3 +}-content as manifestation of increased ordering 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 Zr_1−xNd_xO_2−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 NdO_1.5 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 (298–1273 K) and dilatometry (323–1673 K). Average coefficient of thermal expansion decreased with increasing NdO_1.5 fraction in Zr_1−xNd_xO_2−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 Zr_0.8Nd_0.2O_1.90.