LAUSR

Abstract Single-phase Ruddlesden popper of La2-xSrxCoO4 nanopowders with x = 0.7, 0.9, 1.1 and 1.3, were successfully synthesized by a modified sol-gel method. Structural stability and morphology of the prepared samples were examined using HT-XRD analysis, FE-SEM and SEM techniques. HT-XRD analysis of the samples, in the range of room temperature to 850 °C, revealed that the structure of all samples was tetragonal. The electrical conductivity measurements, in the range of room temperature to 850 °C, indicated that by increasing the temperature the electrical conductivity mechanism inverts from variable range hopping to the nearest-neighbor hopping of small polarons. In addition, it was found that by increasing Sr concentration the structure of the sintered samples becomes more stable. The electrochemical characterization was carried out using the impedance spectroscopy (EIS) measurements on symmetrical cells at three different temperatures, 650 °C, 750 °C and 850 °C. The area specific polarization resistance (ASR) of La2-xSrxCoO4-CGO-La2-xSrxCoO4 symmetrical cell, in oxygen flow, was obtained about 1.07, 0.35, 0.33 and 0.43 Ωcm2 at 850 °C for the samples with x = 0.7, 0.9, 1.1 and x = 1.3, respectively. According to our EIS results, the main rate-limiting step for La2-xSrxCoO4 cathode performance is the dissociation process of oxygen at the surface of cathode at 650 °C and the charge transfer limiting in the cathode/electrolyte at 750 °C and 850 °C. Our results showed that the samples with Sr contents of x = 0.9 and x = 1.1 can be the promising cathodes for IT-SOFC applications.