Phase equilibrium and optical properties of intermediate phases in CaO–Nd2O3–Nb2O5 ternary system at 1200 °C

Subsolidus phase equilibria in the CaO–Nd₂O₃–Nb₂O₅ ternary system and optical properties of the phases formed within this system have been investigated. Twenty-nine samples covering the entire composition range of the ternary oxide system were prepared using the ceramic method. Using powder X-ray diffraction (PXRD) and differential thermal analysis (DSC/TGA), isothermal cross-sections of the ternary system, distinguishing partial subsystems in the subsolidus region at 1200 °C, was constructed. The results highlight the formation of solid solutions and pseudo-binary eutectic systems with limited solid-state solubility and provide insights into the thermodynamic stability of the materials. Additionally, UV–visible diffuse reflectance spectra of calcium and neodymium niobates were analyzed, revealing promising absorption characteristics for photocatalytic and optoelectronic applications. The study emphasizes these materials' potential for designing high-performance sensors and devices with tunable optical properties.