Effects of iron content on the structural evolution,electrical properties and thermochemical stability of BaCo_(0.9-x)Fe_xNb_(0.1)O_(3-δ) ceramic membrane

摘要

Cubic perovskite oxygen permeation materials BaCo_(0.9-x)Fe_xNb_(0.1)O_(3-δ) (BCFN, x = 0.1-0.7) are prepared by the conventional solid state reaction process. The crystal structure development, structural stability, electrical conductivity and oxygen permeation flux are investigated. The introduction of iron makes the formation of cubic perovskite structure for BCFN materials much easier. BCFN exhibits a p-type semiconductor and obeys the thermally activated small polarons hopping mechanism. The electrical conductivity of BCFN increases with increasing temperature and decreases with the Fe-doping concentration. The incorporation of Fe decreases slightly the oxygen permeability of BCFN membranes, but enhances significantly the structure stability of the oxygen permeation membrane in reducing atmosphere. A high oxygen permeation flux of 1.7 ml cm~(-2) min~(-1) at 900 ℃ through 1 mm densified membrane under air/helium condition is obtained for the composition of BaCo_(0.6)Fe_(0.3)Nb_(0.1)O__(3-δ).