Sr 9 La 2 (WO 6 ) 4 containing [WO 6 ] octa-hedra.

A polycrystalline sample of Sr 9 La 2 (WO 6 ) 4 , nona-strontium dilanthanum tetra-kis-[orthotungstate(VI)], was prepared by heating a compacted powder mixture of SrCO 3 , WO 3 , and La 2 O 3 with an Sr:La:W molar ratio of 9:2:4 at 1473 K. X-ray crystal structure analysis was performed for a Sr 9 La 2 (WO 6 ) 4 single-crystal grain grown by reheating the sample at 1673 K. Sr 9 La 2 (WO 6 ) 4 crystallizes with four formula units in the tetra-gonal space group I 4 1 / a and is isotypic with Sr 11 (ReO 6 ) 4 . Two W sites with site symmetries of are located at the center of isolated [WO 6 ] octa-hedra, and four mixed (Sr/La) sites are surrounded by eight to twelve O atoms of the [WO 6 ] octa-hedra. The structure of Sr 9 La 2 (WO 6 ) 4 can be described on the basis of the double-perovskite structure with [WO 6 ] and [(Sr/La)O x ] polyhedra alternately placed, and a vacancy (□).