Layered Bi4BaxV2-xO11-(3x/2)-δ perovskite oxide as solid electrolyte for intermediate temperature solid oxide fuel cells

A continuous series of Bi4BaxV2-xO11-(3x/2)-delta solid solutions are prepared by conventional solid state reactions. The polymorphism and electrical properties of these samples are studied by FT-IR spectroscopy, X-ray diffraction, differential thermal analysis (DTA) and AC impedance. The solid solutions with composition 0.07 <= x <= 0.13 are isostructural with the monoclinic phase alpha-Bi4V2O11. However, orthorhombic beta-phase is observed for x=0.17 and tetragonal gamma-phase is stabilized for x <= 0.30. X-ray and DTA results reveal the occurrence of alpha <-> gamma transition for x <= 0.13, beta <-> gamma transition for x=0.17 and gamma' -> gamma transition for x >= 0.20. AC impedance plots at 280 degrees C for all compositions show greater contribution of grain to ionic conductivity than grain boundary. The highest ionic conductivity, sigma(300 degrees C)=4.456 x 10(-5) S cm(-1) is observed for x=0.17. The ionic conductivity of the substituted compounds is higher than the parent alpha-Bi4V2O11, due to the increased oxygen ion vacancies generated as a result of barium doping. (C) 2010 Elsevier B.V. All rights reserved.