Crystal structure of Ba2La4Ti5O18, member n = 6 of the homologous series (Ba,La)nTin−1O3n of cation deficient perovskite-related compounds

Abstract

Ba₂La₄Ti₅O₁₈ crystallizes in the trigonal system (space group R3) with the unit-cell parameters: a = 5.584 (1) Å; c = 41.176 (8) Å; Z= 3.

The structure has been solved from single crystal X-ray diffraction data to a final R₁ = 0.0285. Ba and La atoms are twelve-fold coordinated and Ti atoms six-fold coordinated. The structure can be described as consisting of identical perovskite-like blocks, five corner-sharing TiO₆ octahedra thick, separated by layers of vacant octahedra. The distortion of the cation and anion sublattices has been analysed and a Ba/La order has been evidenced.