Rietveld refinement of the langbeinite-type mixed-metal phosphate K2Ni0.5Zr1.5(PO4)3

摘要

Dipotassium [nickel(II) zirconium(IV)] tris­(orthophosphate) was prepared from a self-flux in the system K2O–P2O5–NiO–K2ZrF6. The title compound belongs to the langbeinite family and is built up from two [MO6] 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 [PO4] tetra­hedra inter­linked via vertices into a ³ ∞[M 2(PO4)3] framework. Two independent K⁺ cations are located in large cavities of the framework, with coordination numbers to O²⁻ anions of nine and twelve. The K, Ni, and Zr sites are located on threefold rotation axes.