BaAn^IV(PO₄)₂ (An^IV = Th, Np) – A New Family of Layered Double Phosphates

Abstract

Abstract BaTh(PO 4 ) 2 has been synthesized by a wet chemistry route and the new isotype BaNp(PO 4 ) 2 by solid‐state reaction. Although the former has been the subject of several studies since the early 1980s, the crystal structures of both compounds are reported here for the first time. Rietveld analysis shows Ba layers alternating with An(PO 4 ) 2 slabs along the a axis. Although those compounds are isostructural to RbEu(SO 4 ) 2 , these phosphates can be seen as modified yavapaiite derivatives with increased coordination numbers for Ba (XIV) and Th/Np (VIII). Raman and electron absorption spectra highlight the similarities and differences with chemically related compounds.