Preparation of La1-1 Srx Fe1-y MyO3-δ perovskites for solid oxide fuel cell materials

Abstract

The influences of Sr-doping at A-site and Cr-, Ni- and Cu-doping at B-site on the structures and properties of LaFeO3 perovskites were studied. Confirmed by XRD technique, La1-xSrxFe1-yMyO3-d (M = Cr, Ni and Cu; x = 0.3-0.7; y = 0.0-0.3) synthesized by the modified citrate method showed single-phase and ABO3 cubic structure, except that La0.4Sr0.6Fe0.7Ni0.3O3-d contained impurity phase. Using SEM, the morphology of the perovskite oxide discs revealed dense microstructures. The grain sizes of La1-xSrxFe1-yMyO3-d were found to increase with the doped Sr content. The perovskite oxide conductivity measured by DC-4 probe technique displayed that the electrical conductivity of LaFeO3 was improved by the addition of Sr, Cu and Ni. The specific conductivity of La0.4Sr0.6Fe0.8Ni0.2O3-d reached the maximum value of 495.46 S/cm at 550 °C. For thermal expansion analysis, the TEC values of La1-xSrxFe O3-d increased with doping Sr at A-site and doping Cr, Ni and Cu at B-site. Oxygen permeation measurement proved that coating surface catalyst on doped LaFeO3 membrane can enhance the membrane oxygen permeation flux, especially with both-sides catalyst coating. At 1,000 °C, the highest oxygen permeating flux of 72.51 × 10-8 mol/s*cm2 was obtained from La0.4Sr0.6Fe0.8Ni0.2O3-d membrane coated with porous La0.4Sr0.6Fe0.8Ni0.2O3-d on both sides.