A comparative study of high temperature properties of cobalt-free perovskites
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Co-free perovskites with chemical composition Ba0.5Sr0.5Fe0.8M0.2O3-δ (M = Ni, Cu, Zn) were synthesized by the modified Pechini method, and their structure and microstructure were characterized by XRD and SEM. Oxygen content, electrical resistivity and Thermal Expansion Coefficient (TEC) were evaluated in air between room temperature and 900 °C. The high-temperature properties of these perovskites were compared with those of Co containing Ba0.5Sr0.5Fe0.8Co0.2O3-δ perovskite. The highest electrical conductivity was obtained for Ba0.5Sr0.5Fe0.8Cu0.2O3-δ, with values of 47.6 Scm−1 at 544 °C. This same composition also exhibits the highest oxygen vacancies concentration: 3-δ = 2.61 at room temperature. In contrast, the Ba0.5Sr0.5Fe0.8Zn0.2O3-δ, showed lower electrical conductivity suggesting that the Zn+2 ions block electron transport. Co-free perovskites seem to be stable at high temperatures for long term periods. However, these compounds suffered degradation at room temperature in samples stored in air.
KeywordsCobalt-free perovskite SOFC cathode Oxygen separation membranes Ba0.5Sr0.5Fe0.8M0.2O3-δ Dilatometry Conductivity
This work was supported by CNEA (Argentine Atomic Energy Commission), CONICET (Argentine Research Council), UNCuyo and ANPCyT. The authors thank Prof. N. Gonzalez and Mr. Alex Ferrari for English revision of this manuscript.
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