Thermal Analysis and Phase Equilibria of the Molten System Na 3 AlF 6 -NdF 3 -Nd 2 O 3

Phase diagrams of the systems Na 3 AlF 6 -NdF 3 and (Na 3 AlF 6 -NdF 3 ) eut -Nd 2 O 3 were experimentally determined by thermal analysis up to 60 mol.% NdF 3 and 45 mol.% Nd 2 O 3 , respectively. The Na 3 AlF 6 -NdF 3 system was found to be a simple eutectic system with the eutectic point with the following approximate coordinates: 49 mol.% NdF 3 and 905°C. This eutectic composition was then used for the thermal analysis of the (Na 3 AlF 6 -NdF 3 ) eut -Nd 2 O 3 system. The coordinates of the eutectic point of the (Na 3 AlF 6 -NdF 3 ) eut -Nd 2 O 3 system were found to be approximately 46 mol.% Nd 2 O 3 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 Na 3 AlF 6 -NdF 3 system has shown the formation of two new compounds; NaNdF 4 and NdOF. The formation of NdOF is probably the product of the high-temperature hydrolysis between the moisture in the atmosphere and NdF 3 . The XRD analysis of the solidified samples of the (Na 3 AlF 6 -NdF 3 ) eut -Nd 2 O 3 system has shown the formation of the following new compounds: NaNdF 4 , NdOF, NdAlO 3, and NaF.