Generalized electrical conductivity relaxation approach to determine electrochemical kinetic properties for MIECs

Abstract

Electrical conductivity relaxation (ECR) technique has been widely used to determine kinetic properties of mixed ionic and electronic conductors (MIECs). However, this technique is only applicable for reliable determination of kinetic parameters within a confined range of chemical Biot numbers. Since the kinetic properties of the materials are not known a priori, this imposes great difficulties on how to verify the obtained kinetic parameters from obtained ECR data. Further due to the ill-posed nature of ECR problem, the measurement noise could lead to significant uncertainties in the determined kinetic parameters. Herein a generalized ECR (g-ECR) approach is developed by coherently incorporating multiple ECR measurements simultaneously into an inverse algorithm. This new approach is able to improve the accuracy of calculated kinetic parameters and attenuate uncertainties induced by measurement noise over a wider range of chemical Biot numbers than the ECR approach with a single measurement. The capability of both reducing uncertainties and increasing the range of chemical Biot numbers for accurate parameter determination can be achieved by increasing the number of employed ECR measurement responses. A case study of ECR measurement for PrBa(Co0.75Fe0.25)2O5+δ is performed in a mixture gas of N2/Air at 600°C. The kinetic parameters are determined and evaluated using this g-ECR approach. The rationality of using g-ECR approach instead of ECR approach is verified.