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.