Effect of ‘A’-site non stoichiometry in strontium doped lanthanum ferrite based solid oxide fuel cell cathodes

• La1−xSrxCoyFe1−yO3−δ, x = 0.4; y = 0.2 system varying La-site (0.6–0.54) are studied.
• Combustion synthesis technique is used to prepare the powder samples.
• Highest electrical conductivity observed with largest A-site deficit composition.
• Lowest cathode polarization is found with the same composition (0.02 Ω cm2).
• Composition with largest A-site deficiency exhibits best performance (2.84 A cm−2).

Effect of A-site non-stoichiometry in strontium doped lanthanum cobalt ferrite (La1−xSrxCoyFe1−yO3−δ, x = 0.4; y = 0.2) is studied in a systematic manner with variation of ‘A’ site stoichiometry from 1 to 0.94. The perovskite based cathode compositions are synthesized by combustion synthesis. Powder characterizations reveal rhombohedral crystal structure with crystallite size ranging from 29 to 34 nm with minimum lattice spacing of 0.271 nm. Detailed sintering studies along with total DC electrical conductivities are evaluated in the bulk form with variation of sintering temperatures. The electrode polarizations are measured in the symmetric cell configuration by impedance spectroscopy which is found to be the lowest (0.02 Ω cm2 at 800 °C) for cathode having highest degree of ‘A’-site deficiency. The same cathode composition exhibits a current density of 2.84 A cm−2 (at 0.7 V, 800 °C) in anode-supported single cell. An attempt has been made to correlate the trend of electrical behaviour with increasing ‘A’-site deficiency for such cathode compositions.

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