Preparation and crystal structure of Sr5TiNb4O17

The compound Sr5TiNb4O17 was prepared and its crystal structure determined by single-crystal X-ray diffraction. This compound crystallizes with an orthorhombic unit cell (space group Pnnm (No. 58); a = 5.6614(4), b = 32.515(7), c = 3.9525(3) angstrom; Z = 2). The structure consists of alternating perovskite-like slabs offset with respect to each other by a/2 and c/2. The Sr2+ ions occupy two 12-fold coordinated sites within the slabs and a distorted (7 + 1)-fold coordinated site in the gap separating the slabs. Nb5+ and Ti4+ are distributed among the octahedral sites of the sperovskite slabs with preferential ordering of Ti4+ on octahedral sites in the center of the slabs and Nb5+ in the octahedral sites at the edges of the slabs adjacent to the gap. This compound is the n = 5 member of a structural series AnBnO3n+2, (A = Sr; B = Ti,Nb) where n is the number of perovskite layers within each slab