Phase diagram study of the Ln2O3–Nb2O5 (Ln = La, Nd) systems

Phase equilibria in the Ln2O3–Nb2O5 (Ln = La, Nd) binary systems and liquidus temperatures were experimentally established in air atmosphere up to 1800 °C using DSC/TGA analysis combined with a high-temperature equilibration and quenching method. The phase composition and microstructure of the equilibrated samples were characterized by powder X-ray diffraction and scanning electron microscopy, and melting points were confirmed through pyrometric observations. The binary compounds Ln3NbO7, LnNbO4, LnNb3O9 (Ln = La, Nd), and LaNb5O14 were identified. Their crystal structures were refined using Rietveld analysis. The composition and melting point of eutectic/peritectic mixtures in both systems were also determined.