The technique of the differential impedance analysis – Applications for SOFC studies

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The paper presents the technique of Differential Impedance Analysis (DIA), which ensures structural and parametric identification of the impedance model without a preliminary working hypothesis. Its advantages are demonstrated through results obtained from a comparative impedance study of strontium doped lanthanum manganite (LSM) and composite based on LSM and yttria stabilized zirconia (LSM/YSZ), applied as cathode materials in solid oxide fuel cells. DIA identifies three steps in the cathode reaction, as well as the rate limiting stage. It is found that the main contribution in the polarization resistance is due to transport limitations. The analysis shows that the improvement of the LSM/YSZ system for low temperature applications should concern the influence of both the ionic and the electronic conductivity.

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