Al14Ba8La(26.3)Ru18Sr(53.7)O167: a variant of cubic perovskite with isolated RuO6 units.

The crystal structure of the title aluminium barium lanthanum ruthenium strontium oxide has been solved and refined using neutron powder diffraction to establish the parameters of the oxygen sublattice and then single-crystal X-ray diffraction data for the final refinement. The structure is a cubic modification of the perovskite ABO(3) structure type. The refined composition is Ba(0.167)La(0.548)Sr(1.118)Ru(0.377)Al(0.290)O(3.480), and with respect to the basic perovskite structure type it might be written as (Ba(8)La(13.68)Sr(34.32))(Al(13.92)La(12.64)Ru(18.08)Sr(19.36))O(192-x), with x = 24.96. The metal atoms lie on special positions. The A-type sites are occupied by Ba, La and Sr. The Ba atoms are located in a regular cuboctahedral environment, whereas the La and Sr atoms share the same positions with an irregular coordination of O atoms. The B-type sites are divided between two different Wyckoff positions occupied by Ru/Al and La/Sr. Only Al and Ru occupy sites close to the ideal perovskite positions, while La and Sr move away from these positions toward the (111) planes with high Al content. The structure contains isolated RuO(6) octahedra, which form tetrahedral substructural units.