Layered Bi_4Ba_xV_(2-x)O _(11-(3x/2)-δ) perovskite oxide as solid electrolyte for intermediate temperature solid oxide fuel cells

摘要

A continuous series of Bi_4Ba_xV_(2-x)O _(11-(3x/2)-δ) 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 α-Bi_4V _2O_(11). However, orthorhombic β-phase is observed for x=0.17 and tetragonal γ-phase is stabilized for x≤0.30. X-ray and DTA results reveal the occurrence of α?γ transition for x≤0.13, β?γ transition for x=0.17 and γ′→γ transition for x<0.20. AC impedance plots at 280 °C for all compositions show greater contribution of grain to ionic conductivity than grain boundary. The highest ionic conductivity, σ_(300 °C)=4.456×10 ~5 S cm~1 is observed for x=0.17. The ionic conductivity of the substituted compounds is higher than the parent α-Bi_4V _2O_(11), due to the increased oxygen ion vacancies generated as a result of barium doping.