Phase Diagrams of the KF–NaF–K₂NaVF₆ and KCl–NaCl–K₂NaVF₆ Systems

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The phase diagrams of the KF–NaF–K₂NaVF₆ and KCl–NaCl–K₂NaVF₆ systems were determined by the use of thermal analysis and X-ray diffraction analysis. The ternary eutectic point of the KF–NaF–K₂NaVF₆ system is at 62.5 mol% KF, 33 mol% NaF, 4.5 mol% K₂NaVF₆, and 700°C. The minimum point of the KCl–NaCl–K₂NaVF₆ system is at 37 mol% KCl, 57 mol% NaCl, 6 mol% K₂NaVF₆, and 632°C. Dipotassium sodium hexafluorovanadate (III) was found to be a compound which can be represented in terms of K_2±xNa_1\mpxVF₆. Compositions in the vicinity of the minimum point of the KCl–NaCl–K₂NaVF₆ system are considered to be suitable as an electrolyte for the electrorefining or electro-extraction of vanadium.