LAUSR

Abstract The lack of thermodynamic information, such as primary phase fields and liquidus temperatures, in the CaO-SiO 2 -Nb 2 O 5 -La 2 O 3 quaternary system phase diagram has restricted the comprehensive utilization of the niobium (Nb) and rare earth (RE) resources. In this work, the phase equilibria in low basicity region ( w (CaO)/ w (SiO 2 ) 2 -Nb 2 O 5 -(0–15 wt%)La 2 O 3 system at 1373 – 1873 K were experimentally studied by thermodynamic equilibrium experiment, and then, the results were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). Additionally, anoptimized method was proposed to process the compositions of equilibrium liquid phases at different temperatures. According to the experimental results, the univariate line between CaNb 2 O 6 , SiO 2 and LaNbO 4 primary phase fields, interface between CaNb 2 O 6 and SiO 2 primary phase fields and isothermal liquid ussurfaces in SiO 2 primary phase field were determined. Finally, the spatial phase diagram of CaO-SiO 2 -Nb 2 O 5 -La 2 O 3 within specific region was constructed, and furthermore, the phase diagram was also presented inCaO-SiO 2 -Nb 2 O 5 pseudo-ternary system with w (La 2 O 3 )=5 wt%, 10 wt% and 15 wt%. The research results have guiding significance for the improvement of related phase diagram and the comprehensive utilization of Nb and RE resources.