The NaCaAlF₆-Al₂O₃ and Na₃AlF₆-Al₂O₃-NaCaAlF₆ phase diagrams were determined using DTA, x-ray diffraction, quench analysis, and optical microscopy. The NaCaAlF₆-Al₂O₃ system was a simple eutectic system with the eutectic located below 0.5 weight percent NaCaAlF₆. The ternary system was a eutectic system showing solid solution of NaCaAlF₆ in both polymorphs of Na₃AlF₆. Alumina exhibited no appreciable solubility in Na₃AlF₆ and, in the ternary system, less than 2% solubility above 15% NaCaAlF₆. / Master of Science