Rietveld refinement of the langbeinite-type mixed-metal phosphate K(2)Ni(0.5)Zr(1.5)(PO(4))(3)

Dipotassium [nickel(II) zirconium(IV)] tris­(orthophosphate) was prepared from a self-flux in the system K(2)O–P(2)O(5)–NiO–K(2)ZrF(6). The title compound belongs to the langbeinite family and is built up from two [MO(6)] octa­hedra [M = Ni:Zr with mixed occupancy in ratios of 0.21 (4):0.79 (4) and 0.29 (4):0.71 (4), respectively] and [PO(4)] tetra­hedra inter­linked via vertices into a (3) (∞)[M (2)(PO(4))(3)] framework. Two independent K(+) cations are located in large cavities of the framework, with coordination numbers to O(2−) anions of nine and twelve. The K, Ni, and Zr sites are located on threefold rotation axes.