Yb/Sc Co-doped ZrO2 electrolytes enabled by Al2O3 sintering aid: High conductivity and enhanced stability for solid oxide fuel cells (SOFCs)

ScSZ is one of the traditional electrolyte candidates for solid oxide fuel cells (SOFCs) due to its excellent ionic conductivity. Nevertheless, its complex phase structure and high sintering temperature hinder further development. Herein, the effects of Yb2O3 and Al2O3 doping on conductivity and sintering ability as well as the long-term stability in ScSZ electrolyte are studied and discussed in detail. XRD and EIS tests revealed that the ZrO2 electrolyte stabilized by 1 mol% Yb2O3 and 10 mol% Sc2O3 achieved a stable phase structure and high conductivity. Subsequently, the addition of 0.1 mol% Al2O3 sintering aid reduced the densification temperature by more than 100 °C, achieving a density of over 96 % without significant decrease in ionic conductivity, with values of 0.12 S cm−1 in air at 750 °C. Long term stability test reveals that the ScSZ electrolyte doped with Yb2O3 and Al2O3 maintains a stable phase structure and exhibits no significant degradation in electrical performance after being held at 800 °C for 1080 h. In conclusion, the Yb2O3 doped ZrO2 electrolyte with 0.1 mol% Al2O3 sintering aids exhibits a potential candidate material used in SOFCs.