50 mol% indium substituted BaTiO3: Characterization of structure and conductivity

Journal article, 2012

BaTi0.5In0.5O3-delta was prepared by solid state reaction at 1400 degrees C. Rietveld analysis of high resolution X-ray powder diffraction data indicated phase pure as-prepared material that adopts a cubic perovskite structure with a = 4.1536(1) angstrom. Thermogravimetric analysis revealed the presence of significant levels of protons in the as-prepared material and 57% of the theoretically achievable protonation was attained on exposure to a humid environment at 185 degrees C. After hydration the cell parameter increased to 4.1623(1) angstrom. Electrical conductivity was measured both with fixed and variable frequency ac impedance methods as a function of temperature, oxygen-, water vapour- and heavy water vapour partial pressures. In the temperature range 400-800 degrees C a slight increase in the total conductivity with increasing oxygen partial pressure is encountered, characteristic of a contribution from p-type charge carriers. The effect of the water vapour pressure on conductivity below 600 degrees C is much more prominent indicative of dominant proton conduction. At 300 degrees C the total conductivity in wet O-2 was estimated to be 9.30 x 10(-5) S/cm. At T > 800 degrees C the material is a pure oxide ion conductor.