Gadolinium orthophosphate weinschenkite type and phase change in rare earth orthophosphates

Some properties of rare earth orthophosphates have been determined by means of synthesis, X-ray diffraction, infrared absorption spectra, and Raman spectra measurements. The results are: (1) a synthesis of new compounds GdPO4.2H2O weinschenkite type, (2) the salt readily lost its water and changed from the weinschenkite to the xenotime form at about 300°C in air, (3) the change phase in rare earth orthophosphates showed that the weinschenkite phase can give rise to rhabdophane or xenotime phases, and (4) the orthorhombic form DyPO4·1.5H2O is explainable in terms of a mixture of rhabdophane and xenotime-structured material.