Sodium Cerium Phosphate, (Na,Ce)2Ce(PO4)2 ⋅ xH2O, with Mixed Cerium Oxidation States

Abstract A previously unknown double ceric sodium phosphate hydrate Na 1.97 Ce 1.03 (PO 4 ) 2 ⋅ x H 2 O containing both ceric and cerous cations was obtained by the hydrothermal treatment of amorphous ceric phosphate mixed with a sodium hydroxide aqueous solution. The presence of Ce 3+ in the structure was proved by HERFD‐XANES and ESR spectroscopy. Iterative transformation factor analysis of HERFD‐XANES data allowed estimating the content of Ce 3+ as 10 % of the total cerium. Water content of x =0.55 has been determined by thermogravimetric analysis combined with mass‐spectrometry data. The structure of the compound was solved from powder X‐ray diffraction data (S.G. P 2 1 /c a =6.9441(2) Å, b =11.6805(3) Å, c =9.3434(3) Å, β =111.6827(18)°). The new ceric sodium phosphate hydrate has a tunnel structure, where Ce 3+ cations most likely partially occupy Na + positions. The crystal structure of the novel compound has no direct analogues among the crystal structures of double tetravalent metal phosphates.