Synthesis, structure and physical properties of reduced barium titanate Ba2Ti13O22

Polycrystalline sample of the reduced barium titanate Ba{sub 2}Ti{sub 13}O{sub 22} was synthesized by solid state reaction at 1523 K in Ar atmosphere for the first time. The Rietveld refinement using the powder X-ray diffraction data confirmed the sample to be main phase of Ba{sub 2}Ti{sub 13}O{sub 22} having the orthorhombic crystal system, space group Bmab and the lattice parameters of a=11.67058(11) A, b=14.12020(13) A and c=10.06121(9) A, and V=1657.995(20) A{sup 3}. The valence state of Ti was evaluated by both the Ti-O bond distance analysis and the Ti K-edge XANES analysis. The magnetic susceptibility was nearly temperature independent in the range of 60-300 K, suggesting the Van Vleck Paramagnetism. The electrical conductivity at 300 K is approximately 320.50 S/cm, and a semiconducting behavior was observed below room temperature. The Seebeck coefficient showed a negative value of -1.25 {mu}V/K at 300 K, indicating n-type behavior. These facts were confirmed by the results of the present theoretical calculations by the FLAPW method. - Graphical abstract: Temperature dependence of the electrical conductivity of Ba{sub 2}Ti{sub 13}O{sub 22}. A plot of ln {sigma} versus T{sup -1} is shown by open circles, and a plot of ln {sigma} versus T{sup -1/4} is shown bymore » open triangles. Highlights: > Polycrystalline samples of Ba{sub 2}Ti{sub 13}O{sub 22} synthesis by solid state reaction. > Theoretical calculation by FLAPW method. > Electrical property measurements.« less