Phase diagrams of the systems Na₃AlF₆-NdF₃ and (Na₃AlF₆-NdF₃)_eut-Nd₂O₃ were experimentally determined by thermal analysis up to 60 mol.% NdF₃ and 45 mol.% 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 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, NdAlO_3, and NaF.