In order to develop novel cathode materials with high performance for intermediate temperature SOFC (IT-SOFC),Ca and Mn doped rare earth oxides La1-xCaxFe0.9Mn0.1O3-δ(x=0.1,0.3 and 0.5,denoted as LCFM9191,LCFM7391 and LCFM5591) were synthesized by solid state reaction (SSR) method.The formation process,phase structure and microstructure of the synthesized samples were characterized using thermogravimetry/differential scanning calorimetry (TG/DSC),X-ray diffraction (XRD) and scanning electron microscopy (SEM).The thermal expansion coefficients (TEC) of the samples were analyzed at 100-900℃ by thermal dilatometry.The electrical conductivities of the samples were measured with direct current (DC) four-terminal method from 300 to 850 ℃.The results indicated that the samples (x=0.1 and 0.3) exhibited a single phase with orthorhombic and cubic perovskite structure,respectively after being sintered at 1200 °C for 3 h.The electrical conductivity of the samples increased with temperature up to a maximum value,and then decreased.The small polaron hopping w as regarded as the conducting mechanism for synthesized samples at T≤600 ℃.The negative temperature dependence occurring at higher temperature was due to the creation of oxygen vacancies for charge balance.LCFM7391 had higher mixed conductivity (＞100 S/cm) at intermediate temperature and could meet the demand of cathode material for IT-SOFC.In addition,the average TECs of LCFM9191 and LCFM7391were 11.9× 10 6 and 13.1 × 10-6 K-1,respectively,which had good thermal match to the common electrolytes.
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