Sr9La2(WO6)4 containing [WO6] octahedra

A polycrystalline sample of Sr9La2(WO6)4, nonastrontium dilanthanum tetrakis[orthotungstate(VI)], was prepared by heating a compacted powder mixture of SrCO3, WO3, and La2O3 with an Sr:La:W molar ratio of 9:2:4 at 1473 K. X-ray crystal structure analysis was performed for a Sr9La2(WO6)4 single-crystal grain grown by reheating the sample at 1673 K. Sr9La2(WO6)4 crystallizes with four formula units in the tetragonal space group I41/a and is isotypic with Sr11(ReO6)4. Two W sites with site symmetries of \overline{1} are located at the center of isolated [WO6] octahedra, and four mixed (Sr/La) sites are surrounded by eight to twelve O atoms of the [WO6] octahedra. The structure of Sr9La2(WO6)4 can be described on the basis of the double-perovskite structure with [WO6] and [(Sr/La)Ox] polyhedra alternately placed, and a vacancy (□).