STRUCTURE OF BA4NB14O23

Single crystals of Ba4Nb14O23 were obtained by heat treatment of a pel leted mixture of Ba5Nb4O15, Nb2O5 and Nb at 1725 K in an Ar atmosphere . High-resolution electron microscopy studies showed the structure to be an intergrowth of the BaNbO3 perovskite structure and the NbO struc ture. The structure model was refined using X-ray single-crystal diffr action data. Characteristic structural units are triple chains of come r-sharing Nb6 octahedra, parallel to the c axis and separated by perov skite-type columns. Crystal data: barium oxoniobate, Ba4Nb14O23, M(r) = 2218.0, orthorhombic, Cmmm, a = 20.79 (1), b = 12.453 (6), c = 4.149 (1) angstrom, V = 1074 (1) angstrom3, Z = 2, D(x) = 6.86 g cm-3, lamb da(Cu Kalpha) = 1.5418 angstrom, F(000) = 1964, T = 295 K, R = 0.031 f or 419 observed unique reflections.