Characterization of Cathode Materials Ln<sub>0.7</sub>Sr<sub>0.2</sub>Ca<sub>0.1</sub>Co<sub>0.7</sub>Fe<sub>0.3</sub>O<sub>2.85 </sub>(Ln=La, Pr and Nd) Synthesized by Microwave Sintering Techniques

Abstract

Sr, Ca and Fe doped cathode materials Ln0.7Sr0.2Ca0.1Co0.7Fe0.3O2.85(LnSCCF, Ln=La, Pr and Nd; abbreviated as L-72173, P-72173 and N-72173) were synthesized by microwave sintering (MWS) techniques. The formation process, phase structure and composition were characterized using TG/DTA, XRD and EDS. The thermal expansion behavior of the samples was analyzed in the range of 20-950 °C by thermal dilatometer. The electrical conductivity of the samples was measured with DC four-terminal method from 25 to 900 °C. The X-ray diffraction shows that the samples exhibit a single phase with rhombohedral or cubic perovskite structure after sintered at 1200 °C for 20 min. The electrical conductivity of the samples increases with temperature up to a maximum, and then decreases gradually at higher temperature owing to the creation of oxygen vacancies. The small polaron hopping is regarded as the conducting mechanism (T 550 °C). L-72173 has higher mixed conductivity ( >300 S·cm-1) in 550-800 °C. The average TECs of L-72173, P-72173 and N-72173 are 1.389× 10-5K-1, 1.417 × 10-5K-1and 1.416 × 10-5K-1in the range of 25-800 °C, respectively. They are thermally matched to the GDC better than the YSZ and SDC.