Co-substitution design: a new glaserite-type rare-earth phosphate K 2 RbSc(PO 4 ) 2 with high structural tolerance.

An alkali rare-earth phosphate K 2 RbSc(PO 4 ) 2 was successfully obtained as a derivative of glaserite-type K 3 Na(SO 4 ) 2 by co-substitution of K(1)O 12 → RbO 12 , K(2)O 10 → KO 7 , NaO 6 → ScO 6 and SO 4 → PO 4 , while maintaining the original anionic framework. K 2 RbSc(PO 4 ) 2 exhibits a layered [Sc(PO 4 ) 2 ] ∞ framework built from ScO 6 octahedra and PO 4 tetrahedra, with K and Rb residing in the interlayers. Its isostructural lanthanide analogues K 2 RbEr(PO 4 ) 2 and K 2 RbLu(PO 4 ) 2 , inspired by an elemental substitution strategy, were also prepared by a high-temperature solid state reaction. The successful substitution indicates that the skeleton of K 2 RbSc(PO 4 ) 2 is stable with high structural tolerance, which can provide a possibility for substitution of resident ions to obtain diverse structural types and applications.