The solid solution K(3.84)Ni(0.78)Fe(3.19)(PO(4))(5)

The title compound, tetra­potassium tetra­[nickel(II)/iron(III)] penta­kis­(orthophosphate), K(3.84)Ni(0.78)Fe(3.19)(PO(4))(5), has been obtained from a flux. The structure is isotypic with that of K(4)MgFe(3)(PO(4))(5). The three-dimensional framework is built up from (Ni/Fe)O(5) trigonal bipyramids with a mixed Fe:Ni occupancy of 0.799 (8):0.196 (10) and isolated PO(4) tetra­hedra, one of which is on a general position and one of which has -4.. site symmetry. Two K(+) cations are statistically occupied and are distributed over two positions in hexa­gonally shaped channels that run parallel to [001]. One K(+) cation [occupancy 0.73 (3)] is surrounded by nine O atoms, while the other K(+) cation [occupancy 0.23 (3)] is surrounded by eight O atoms.