Potassium ditin(IV) tris­[phosphate(V)], KSn2(PO4)3

The title compound, KSn2(PO4)3, belongs to the NASICON-type family of phosphates with the space group R . Its structure is constructed by very regular [with P—O distances ranging from 1.513 (6) to 1.522 (6) Å] PO4 tetra­hedra and SnO6 octa­hedra on the 3. axis, which are linked by O atoms, forming an [Sn2(PO4)3] framework. The K atoms occupy the . axis sites and are located in the voids of this arrangement. The crystal studied was a merohedral twin with twin law (010 100 00) and a component ratio of 0.580 (7):0.420 (7)

RbSn2(PO4)3, a NASICON-type phosphate

The title compound, rubidium ditin(IV) tris­(phosphate), RbSn2(PO4)3, belongs to the NASICON-type family of phosphates and crystallizes in the space group R . The structure is composed of PO4 tetra­hedra (1 symmetry) and two slightly distorted SnO6 octa­hedra, both with 3. symmetry, which are inter­linked through corner-sharing O atoms to form a 3 ∞[Sn2(PO4)3]− framework. The Rb+ cations are located on threefold inversion axes in the voids of this framework and exhibit a coordination number of 12. The crystal studied was twinned by merohedry with a component ratio of 0.503:0.497

Al0.5Nb1.5(PO4)3

Single crystals of the title compound, aluminium niobium triphosphate, Al0.5Nb1.5(PO4)3, have been synthesized by a high-temperature reaction in a platinium crucible. The AlIII and NbV atoms occupy the same site on the axis, with disorder in the ratio of 1:3. The fundamental building units of the title structure are isolated Al/NbO6 octa­hedra and PO4 tetra­hedra (. 2 symmetry), which are further inter­locked by corner-sharing O atoms, leading to a three-dimensional framework structure with infinite channels along the a axis