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

Subsolidus phase equilibria in the CaO–Nd 2 O 3 −Nb 2 O 5 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.