Precipitation of Rare Earth Phosphates from NaCl-2CsCl Eutectic Based Melts

The reaction between 15 rare earth chlorides (yttrium, lanthanum and all the lanthanides except for promethium) and sodium orthophosphate was studied in NaCl-2CsCl eutectic based melts between 550 and 750 oC under an inert atmosphere. Rare earth phosphates were precipitated from the melt and their composition determined from chemical analysis, vibrational spectroscopy and X-ray powder diffraction measurements. The effects of temperature and the initial phosphate-to-rare earth mole ratio in the melt on the phase composition of the precipitated phosphates was investigated Over 99.9% precipitation could be achieved and the mole ratio required varied between 2 and 6. The minimum excess of phosphate precipitant required for complete precipitation from the melt was determined.