High temperature phase stabilities and electrochemical properties of InBaCo 4− xZn xO 7 cathodes for intermediate temperature solid oxide fuel cells

Abstract

InBaCo 4− x Zn x O 7 oxides have been synthesized and characterized as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFC). The effect of Zn substitution for Co on the structure, phase stability, thermal expansion, and electrochemical properties of the InBaCo 4− x Zn x O 7 has been investigated. The increase in the Zn content from x = 1 to 1.5 improves the high temperature phase stability at 600 °C and 700 °C for 100 h, and chemical stability against a Gd 0.2Ce 0.8O 1.9 (GDC) electrolyte. Thermal expansion coefficient (TEC) values of the InBaCo 4− x Zn x O 7 ( x = 1, 1.5, 2) specimens were determined to be 8.6 × 10 −6 to 9.6 × 10 −6/°C in the range of 80–900 °C, which provides good thermal expansion compatibility with the standard SOFC electrolyte materials. The InBaCo 4− x Zn x O 7 + GDC (50:50 wt.%) composite cathodes exhibit improved cathode performances compared to those obtained from the simple InBaCo 4− x Zn x O 7 cathodes due to the extended triple-phase boundary (TPB) and enhanced oxide-ion conductivity through the GDC portion in the composites.