Synthesis, Materials and Electro-Conductive Properties of Bi-based Cathodes for IT-SOFC
Date Issued
2015
Date
2015
Author(s)
Chen, Yu-Han
Abstract
M0.6Sr0.4Co0.2Fe0.8O3 (M=La, Pr, Bi) and BiFeO3-based cathodes were synthesized by a modified EDTA-citrate method. One La0.6Sr0.4Co0.2Fe0.8O3 was synthesized by colloidal mixing/solid state sintering, and used as a comparable case. In order to study the homogeneity, two La0.6Sr0.4Co0.2Fe0.8O3 powders were densified and analyzed by quantitative EDS. Detail study of quantitative XRD was done to analyze the impurity phases and the solid solution limit of Co-doping, so to increase the total conductivity of the BiFeO3-based cathodes. Besides, the porosity of cathode needs control by sintering, of which the behavior has been investigated on sintering curves and correlates to the crack formation in cathode layer. Conduction mechanisms (double exchange, small polaron, and oxygen ions conduction) were studied by measuring total conductivity, X-ray photoelectron spectroscopy (XPS) and TGA analyses on two series cathodes, LnSCF6428 series and BiFeO3-based cathodes. The more the cobalt content is, the higher the conductivity. The results of XPS showed that the dense and porous Bi0.7Sr0.3Co0.04Fe0.96O3 at room temperature was mainly Fe3+ and oxygen vacancies on surface, implying ionic conductivity would dominate at high temperature.
Subjects
conductivity
cathode
perovskite
XPS
conduction mechanism
Type
thesis
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