Structure, electrical conductivity and oxygen permeability of Ba0.6Sr0.4Co1−xTixO3−δ ceramic membranes

Abstract

Cubic perovskite oxides, Ba0.6Sr0.4Co1−xTixO3−δ (BSCT, x=0.12–0.30) are prepared by conventional solid state reaction process as oxygen permeation membranes. The effects of Ti-doping on the crystal structure, electrical conductivity and oxygen permeability are investigated. The chemical stability in low oxygen partial pressure atmospheres is enhanced by Ti-doping. The partial substitution of Ti for Co is charge-compensated by the reduction of oxygen vacancy concentration in BSCT. Both the electrical conductivity and the oxygen permeation flux of BSCT decrease with Ti doping level. The large bonding energy of Ti–O and the decreased lattice free volume with Ti substitution lead to increased activation energy of oxygen permeation, which, combined with the decreased oxygen vacancy concentration, is responsible for the decreased oxygen permeation flux. Nevertheless, sufficiently high permeation fluxes, ca. 2.12 and 1.46mLcm−2min−1 at 900°C, are obtained for the samples with x=0.12 and 0.30, respectively, which were comparable to that of the well known Ba0.6Sr0.4Co0.8Fe0.2O3−δ (BSCF5582) material. Furthermore the BSCT material shows much better phase stability compared to BSCF5582 material under oxygen permeation condition. The prepared BSCT materials are promising candidates for oxygen separation or POM applications.