SYNTHESIS AND CRYSTAL-STRUCTURE OF BA2TI13O22 - A REDUCED FORM OF BATI5O11 BY THE TITANIUM INSERTION

A new member of barium titanate compounds Ba2Ti13O22 was synthesized b y the reaction of BaTiO3, Ti2O3, and TiO at 1853 K in an argon atmosph ere. It crystallizes in the orthorhombic system, space group Bmab, a = 11.6550(8) angstrom, b = 14.1062(8) angstrom, c = 10.0535(9) angstrom , V = 1652.9(2) angstrom3, and Z = 4. The structure was determined fro m a single-crystal X-ray diffraction study and refined to the conventi onal values of R = 0.055 and wR = 0.043 for 2050 observed reflections. The closest packing structure of Ba and O atoms in Ba2Ti13O22 is iden tical with that in the BaTi5O11 structure. The vacant octahedral O6 in terstices in BaTi5O11 are completely occupied by the additional titani um cations in the present Ba2Ti13O22, and the face-sharing Ti2O9 doubl e group with a short Ti-Ti distance of 2.730(2) angstrom is formed as in the hexagonal BaTiO3 structure. (C) 1994 Academic Press, Inc.