Investigation of oxygen ion transport and surface exchange properties of PrBaFe2O5+δ

Abstract

The oxygen transport properties and chemical stability of PrBaFe2O5+δ (PBF) double-perovskite oxide were systematically investigated as a chemically stable, highly oxygen-permeable membrane and solid oxide fuel cell (SOFC) electrode under a CO2-containing or reducing atmospheres. The oxygen permeation flux of 0.7 mm-thick samples and the oxygen ion conductivity were 4.7 × 10−1 mL∙cm−2 min−1 and 0.12 S∙cm−1 at 900 °C, respectively, which are comparable to those of PrBaCo2O5+δ, exhibiting the most superior performance among oxides with a double-perovskite structure. Moreover, the bulk diffusion and surface exchange coefficients estimated from the electrical conductivity relaxation analysis were generally comparable to those of PrBaCo2O5+δ. The characteristic thickness estimated from the membrane and conductivity relaxation tests was ∼0.6 mm at 900 °C. The results indicate the significant influence of the surface exchange reaction on the permeability within a thickness of 0.5–1.7 mm. The PBF double-perovskite oxide exhibited superior chemical stability, compared to typical oxides such as PrBaCo2O5+δ under a CO2-containing atmosphere. All results suggest that PrBaFe2O5+δ exhibits high oxygen diffusivity with high chemical stability under CO2-containing or reducing atmospheres.