The effect of nano-sized Al2O3 and CO2O3 addition on the properties of fluorite-type ceria-based oxide composite electrolytes for SOFC applications

Abstract

The present work focuses on the influence of nano-sized Al2O3 and Co2O3 addition on the microstructure, mechanical and electrical properties of the solid state compositions Ce0.8Gd0.2O2-δ, Ce0.8Sm0.2O2-δ, Ce0.8Sm0.1Nd0.1O2-δ and (La0.75Sr0.2Ba0.05)0.175Ce0.825O2-δ synthesized via solid state reactions. The use of nano-sized aluminum oxide enables its uniform distribution in the volume of the electrolyte and improves its mechanical properties. The introduction of cobalt oxide reduces the temperature of obtaining gastight ceramic samples and prevents the formation of second phases (lowconducting ReAlO3, where Re: rare earth element) during sintering. Moreover, it was found that the simultaneous introduction of aluminum and cobalt oxide additives in Gddoped ceria can increase the microhardness of the electrolyte and its stability in a reducing atmosphere of H2+3%H2O (tests carried out for 250 hours). The influence on the electrical conductivity is ambiguous. In the case of the two-component systems Ce0.8Gd0.2O2-δ+2mol%Al2O3+1mol.%Co2O3 and Ce0.8Sm0.2O2-δ+2mol%Al2O3+1mol.%Co2O3 the electrical conductivity increases, as compared with basic electrolytes Ce0.8Gd0.2O2-δ and Ce0.8Sm0.2O2-δ, while in the case of the multi-component systems the electrical conductivity decreases.