Solid oxide fuel cells (SOFCs) have tremendous potential for power generation applications. Unfortunately, the full potential of SOFCs has not been obtained due to the extreme thermal, mechanical, and electrochemical loading conditions that the constituent parts are placed under. Reducing the SOFC operating temperature would increase the cell design flexibility and allow for the use of lower cost materials. Recent work has presented a novel cathode material (BaxSr1-xCo1- yFey03-δ) that can effectively extend the oxygen reduction zone over traditional materials through mixed ionic and electronic conductivity, resulting in excellent power densities at intermediate temperatures. The increased conductivity is, however, accompanied by a large coefficient of thermal expansion that can cause creep and possible component failure. It has also been shown that more ionically conductive materials display increased creep rates (up to four orders of magnitude larger than zirconia) and thermal expansion coefficients (approximately twice that of zirconia). Despite the potential importance of this material, there have been to date relatively few studies on the high temperature mechanical properties, especially those considering the influence of stress and oxygen partial pressure. The primary aim of this proposal is to investigate the effect of mechanical loads on the mechanical constitutive behavior and ionic conductivity of a novel mixed ionic electronic conductive material at elevated temperatures.
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ET Wefring, FH Schader, KG Webber, M-A Einarsrud, and T Grande, “Electrical conductivity and ferroelastic properties of Ti-substituted solid solutions (1 − x) BiFeO3 – xBi0.5K0.5TiO3,” Journal European Ceramic Society, 36, 497–506 (2016).
PT Geiger, O Clemens, NH Khansur, M Hinterstein, MG Sahini, T Grande, P Tung, JE Daniels, and KG Webber, “Nonlinear mechanical behaviour of Ba0.5Sr0.5Co0.8Fe0.2O3-δ and in situ stress dependent synchrotron X-ray diffraction study”, Solid State Ionics, 300, 106–113 (2017)
PT Geiger, N Khansur, K Rieß, A Martin, JE Daniels, and KG Webber, “Stress-dependent Crystal Structure of Lanthanum Strontium Cobalt Ferrite by In situ Synchrotron X-ray Diffraction”, Journal of Applied Physics 123(7), 075104 (2018)