Thermal Analysis and Phase Equilibria of the Molten System Na3AlF6 – NdF3 – Nd2O3

Abstract Phase diagrams of the systems Na3AlF6 – NdF3 and (Na3AlF6 – NdF3)eut – Nd2O3 were experimentally determined by thermal analysis up to 60 mol % of NdF3, and 45 mol % of Nd2O3, respectively. The Na3AlF6 – NdF3 system was found to be a simple eutectic system with the eutectic point with the following approximate coordinates: 49 mol % NdF3, and 905°C. This eutectic composition was then used for the thermal analysis of the (Na3AlF6 – NdF3)eut – Nd2O3 system. The coordinates of the eutectic point of the (Na3AlF6 – NdF3)eut – Nd2O3 system were found to be at approximately 46 mol % Nd2O3 and 733°C. After the thermal analysis, the X – ray diffraction analysis of the solidified samples of both systems was performed. The XRD analysis of the Na3AlF6 – NdF3 system has shown the formation of two new compounds; NaNdF4 and NdOF. The formation of NdOF is probably the product of the high temperature hydrolysis between the moisture in the atmosphere and NdF3. The XRD analysis of the solidified samples of the (Na3AlF6 – NdF3)eut – Nd2O3 system has shown the formation of the following new compounds; NaNdF4, NdOF, NdAlO3, and NaF.