Wei Wen-Cheng J, Huang Der-Rong, Wang Dan
Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan.
Materials (Basel). 2016 Nov 14;9(11):922. doi: 10.3390/ma9110922.
(Bi,Sr)FeO (BSF) cathode materials doped with either Co, Ni or Mn are synthesized by an ethylene diamine tetra-acetic acid (EDTA)-citrate complexing method, and the effects of the doping level on the mixed electronic-ionic conductivity at various temperatures are studied up to 800 °C. The phase purity and solid solution limit are investigated by X-ray diffraction (XRD). The ionic conductivity is measured by the four-probe direct current (DC) method, the valence state of Fe and Mn by X-ray photoelectron spectroscopy (XPS), and the oxygen non-stoichiometry by differential thermo-gravimetric analysis (TGA). The doped ferrites show interesting electronic conductivity dependent on the testing temperature, implying two conductive mechanisms, either controlled by double exchange at lower temperatures or small polaron (electron-oxygen vacancy) conduction at temperatures greater than 400 °C. The results of Co-doped BSF (S50C20) show the best mixed conductivity among the ferrites, and this is used to assemble cells. The cell with a S50C20 cathode in the region of 600-800 °C is improved by 15% in maximum power density greater than the cell with LaSrCoFeO (LSCF) due to the balanced contribution from oxygen ions, vacancies and electrons.
采用乙二胺四乙酸（EDTA）-柠檬酸盐络合法合成了掺杂Co、Ni或Mn的（Bi,Sr）FeO（BSF）阴极材料，并研究了掺杂水平对高达800℃时不同温度下混合电子-离子电导率的影响。通过X射线衍射（XRD）研究相纯度和固溶极限。采用四探针直流（DC）法测量离子电导率，用X射线光电子能谱（XPS）分析Fe和Mn的价态，用差示热重分析（TGA）测定氧非化学计量比。掺杂铁氧体显示出有趣的电子电导率，其取决于测试温度，这意味着两种导电机制，即在较低温度下由双交换控制，或在高于400℃的温度下由小极化子（电子-氧空位）传导。Co掺杂的BSF（S50C20）的结果显示出在铁氧体中具有最佳的混合电导率，并用于组装电池。由于氧离子、空位和电子的平衡贡献，在600-800℃范围内具有S50C20阴极的电池的最大功率密度比具有LaSrCoFeO（LSCF）的电池提高了15%。
