The First Structure of a Cerium(IV) Phosphate: Ab Initio Rietveld Analysis of Ce^IV(PO₄)(HPO₄)_0.5(H₂O)_0.5

Abstract

Layer apparent: Crystalline cerium(IV) phosphates have been studied for a long time as ion exchangers, but their structures have remained unknown. The structure of a cerium(IV) phosphate has been determined (see picture: tetrahedra PO4, yellow Ce, blue O (water)) and clearly explains a notable feature of this compound, its inability to intercalate amines. The X‐ray study is supported by solid‐state NMR spectroscopy investigations.

Cerous phosphate gels: Synthesis, thermal decomposition and hydrothermal crystallization paths

“…The unit cell parameters refined for a well crystallized sample are а = 21.023(2) Å, b = 6.5586(8) Å, с = 6.9554(8) Å and β = 91.98(1)°, which agrees satisfactorily with the earlier data for this compound (Fig. S3) [13].…”

“…6 and S2 correspond to the Ce(PO 4 )(HPO 4 ) 0.5 (H 2 O) 0.5 phase, the structure of which was solved by Nazaraly et al [13]. The unit cell parameters refined for a well crystallized sample are а = 21.023(2) Å, b = 6.5586(8) Å, с = 6.9554(8) Å and β = 91.98(1)°, which agrees satisfactorily with the earlier data for this compound (Fig.…”

“…Tetravalent cerium is thought not to form individual neutral orthophosphates [12], and Ce +4 hydroorthophosphates are typically amorphous substances of variable composition. Nevertheless, the formation of crystalline Ce +4 hydroorthophosphates was recently reported by Nazaraly et al [13,14]. Possible practical applications of such compounds were discussed earlier.…”

“…For instance, Alberti et al [15] have reported high ion exchangeability of cerous phosphates, Barboux et al [16] have described their noticeable proton conductivity. Nazaraly et al [13,14] have indicated the possible use of cerous phosphates as sorbents and heterogeneous catalysts.…”

“…For example, Nazaraly et al [13,14] were the first to succeed in the preparation of crystalline Ce +4 hydroorthophosphate, Ce(PO 4 )(HPO 4 ) 0.5 (H 2 O) 0.5 , by hydrothermal treatment of a cerium dioxide solution in orthophosphoric acid. They also solved the structure of this compound: it has a monoclinic system and possesses a layered structure (space group С2/с; unit cell parameters а = 21.0142(3) Å, b = 6.55082(7) Å, с = 6.94382(6) Å, β = 91.983(1)°, V = 955.32(2) Å 3 ).…”