Synthesis and properties of Sm3+-deficient Sm1−xBaCo2O5+δ perovskite oxides as cathode materials

Double-layered perovskite oxides of Sm1−xBaCo2O5+δ (S1−xBCO) with various A-site Sm3+-deficiencies (x = 0.00–0.08) were synthesized and evaluated as cathode materials of intermediate-temperature solid oxide fuel cells (IT-SOFCs). The Sm3+-deficiency content in S1−xBCO was limited up to x = 0.05, and higher content x = 0.08 caused impurity phase. S1−xBCO oxides were chemically stable with GDC electrolyte at 1050 °C and below. Introduction of Sm3+-deficiency caused decreased oxygen content and increased concentration of oxygen vacancy in S1−xBCO. Electrical conductivities of S1−xBCO decreased with increasing temperature in air, and also changed with the Sm3+-deficiency content. Electrochemical performance of S1−xBCO cathodes were characterized by impedance spectra measurement based on symmetric cells. Higher Sm3+ deficiency content has resulted in decreased area specific resistances (ASRs) and activation energy (Ea), i.e. enhanced electrochemical reaction reactivity for the S1−xBCO cathodes. Among the studied samples, the S0.95BCO (x = 0.05) oxide showed the best electrochemical performance with ASR values of 0.316 Ω cm2 at 600 °C, 0.137 Ω cm2 at 650 °C, 0.068 Ω cm2 at 700 °C and 0.038 Ω cm2 at 750 °C respectively, thus itʹs a promising cathode material of IT-SOFCs.