The monoclinic form of trilithium dichromium(III) tris(orthophosphate)

Abstract

The monoclinic form of trilithium dichromium(III) tris(orthophosphate), Li3Cr2(PO4)3, was prepared by the reactive halide flux method. The structure of the title compound is composed of a three-dimensional anionic framework with composition ∞ 3[Cr2(PO4)3]3− and Li+ ions situated in the empty channels. The rigid framework built up from CrO6 octahedra and PO4 tetrahedra is the same as that found in other monoclinic Li3M2(PO4)3 (M = Fe, Sc, V) phases. The three Li+ cations of Li3Cr2(PO4)3 are unequally disordered over six crystallographically different sites. The classical charge balance of the title compound can be represented as [Li+]3[Cr3+]2[P5+]3[O2−]12. Solid-state UV/Vis spectra indicate that the crystal filed splitting (Δ0) of the Cr3+ ion is around 2.22 eV.