Bi-doping effects on the structure and oxygen permeation properties of BaSc 0.1Co 0.9O 3− δ perovskite membranes

Abstract

In this work, we investigate the effect of partial substitution of bismuth oxide on BaSc 0.1Co 0.9O 3− δ perovskite membranes. Doping was carried out in the A-site (Ba 1− x Bi x Sc 0.1Co 0.9O 3− δ ) and B-site (BaBi x Sc 0.1Co 0.9− x O 3− δ ). Bi doping at or below 10% ( x ≤ 0.10) in both sites resulted in significant increase of oxygen flux, up to two orders of magnitude at the low to medium temperature range (650–850 °C) as compared to non-doped disk membranes. Among all compositions, B-site doped x = 0.05 showed the highest oxygen fluxes, reaching 2.17 ml min −1 cm −2 at 950 °C. These results suggest that Bi doping at or below 10% conferred superior ionic oxygen diffusion transport, owing to the formation of cubic structures. Further increases in the Bi-doping amount formed non-cubic structure delivering very low oxygen fluxes. The structure transition phenomena from non-cubic to cubic crystal lattices occurred for non-doped and A-site doped membrane with 20 and 30% mole bismuth oxide in excess of 800 °C, concomitantly with increases in oxygen fluxes and sharp rise of electrical conductivity. A-site and B-site doped x = 0.05 compounds exposed to nitrogen atmosphere at 850 °C for 7 days showed reasonable stable structure.