Cobalt doped lanthanum silicates La10Si6-xCoxO27-x/2 (x=1.5, 1.0, 0.8, 0.6, 0.4, 0.2) were successfully synthesized by sol-gel process. The effect of doping Co on the thermal expansion and the ionic conductivity was investigated. The results of XRD analysis showed that the unit volumes of La10Si6-xCoxO27-x/2 (x=1.5, 1.0, 0.8, 0.6, 0.4, 0.2) increase with cobalt content. In addition, the thermal expansion coefficient increased with cobalt content. La10Si5.2Co0.8O26.6 exhibited the highest ionic conductivity of 3.33×10-2 S/cm at 800°C. La10Si6-xCoxO27-x/2 showed low activation energies of around 0.7eV above 600°C. These show that La10Si6-xCoxO27-x/2 can be a potential electrolyte for IT-SOFC.
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