Incorporation of thorium in the zircon structure type through the Th1-xErx(SiO4)1-x(PO4)x thorite-xenotime solid solution

Pure powdered compounds with a general formula Th1-xErx(SiO4)1-x(PO4)x belonging to the zircon-xenotime were successfully synthesized under hydrothermal conditions (250°C, 7 days) as recently reported for the preparation of coffinite. Therefore a thorough combined PXRD, EDS, EXAFS, μ-Raman and FTIR analyses showed the formation of solid solution in agreement with the Vergard’s law. Moreover, the examination of the local structure shows that the Th-O distances remain close to those found in ThSiO4. Whereas, the Er-O distances show big decrease from 2.38(14) Å to 2.34(7) Å when increasing the erbium content from x = 0.2 to x = 1. The variation of the local structure also affects the PO4 3- groups that are surely distorted in the structure.