Fabrication and characterization of Ca2+, Sr2+, Ba2+, Sm3+, and La3+ co-doped ceria-based electrolyte powders for low-temperature anode-supported solid oxide fuel cells

In this study, CeO2-based electrolytes are synthesized by a sol-gel method. Ce0.8Sm0.2O1.9, Ce0.8Sm0.15Ca0.05O1.875, Ce0.8Sm0.15Ca0.025Sr0.025O1.875 (S15CS05DC), Ce0.8Sm0.15La0.05O1.9, (La0.77Sr0.2Ba0.03)0.15Ce0.85O1.908, and (La0.77Sr0.2Ba0.03)0.2Ce0.8O1.877 specimens are prepared at sintering temperature 1300 °C for either 2 h or 4 h. The microstructures and electrical properties of the electrolytes are analyzed using X-ray diffraction, scanning electron microscopy, and alternating current (AC) impedance spectroscopy. All samples are cubic fluorite structure. It is found that while Ca2+ and Sr2+ contribute to grain growth, Sm3+ and La2+ inhibit it. The conductivity increases with temperature in a linear manner and reaches approximately 0.16 S·cm−1 at 800 °C for the 4 h-sintered S15CS05DC sample. Six anode-supported cells are fabricated and tested at 600 °C-800 °C. Cell-C has the highest maximum power density (0.96 W·cm−2) at 800 °C. It is also found that ohmic resistance predominantly determines the total cell resistance at temperatures above 700 °C.