Mechanical and electrical properties of Al2O3/Ce0.8Y0.2O1.9 composite electrolytes

The Al2O3/Ce0.8Y0.2O1.9 composites, with Al2O3 concentration ranging from 0 to 10 mol%, were prepared by a low-temperature combustion process. The effects of Al2O3 addition on the flexural strength and electrical conductivity of Y3+-doped ceria were investigated, and the mechanism was analyzed. The experimental results showed that Al2O3 enhanced significantly the flexural strength of the as-sintered Ce0.8Y0.2O1.9. The flexural strength was 270 MPa for the specimen containing 10 mol% Al2O3 while the flexural strength of the undoped Ce0.8Y0.2O1.9 specimen was only 121 MPa. Impedance analysis showed that ionic conductivity of the Al2O3/Ce0.8Y0.2O1.9 composite electrolytes decreased and the activation energy increased when the concentration of Al2O3 was within the solubility. When the content of Al2O3 was above its solubility limit in Ce0.8Y0.2O1.9, the bulk resistance was constant and the grain boundary conductivity increased because of the “scavenging” effect of Al2O3. When the concentration of Al2O3 was over 5 mol%, the grain boundary conductivity began to reduce because of the “blocking” effect of Al2O3 particles at the grain boundaries. The activation energy for the bulk conductivity and the grain boundary conductivity retained constant when the concentration of Al2O3 was over its solubility limit in Ce0.8Y0.2O1.9.