Oxygen-ion conductivity and mechanical properties of Lu2O3-doped ZrO2 as a solid electrolyte

The characteristics of Lu₂O₃-doped ZrO₂ as a solid electrolyte material were investigated in terms of its oxygen ion conductivity and flexural strength to realize its electrolytic function at intermediate and high temperatures. The effect of doping Lu³⁺, which has a high nuclear charge electric field strength, was examined through impedance spectroscopy, open-circuit potential measurements, and bending tests. The results with Lu₂O₃ dopant were compared with those obtained with a widely used dopant, Y³⁺, having a similar ionic radius with Lu³⁺, as well as a dopant that provides high ionic conduction, Sc³⁺, having a smaller ionic radius with Zr⁴⁺. The results revealed that, at the same dopant concentration, both the ionic conductivity and the flexural strength of Lu₂O₃-doped ZrO₂ are higher than those of the widely used Y₂O₃-doped ZrO₂. The conductivity of 8 mol% Lu₂O₃-doped ZrO₂ surpassed that of 8 mol% Sc₂O₃-doped ZrO₂ in the range of 800–950 °C (0.153 S/cm vs. 0.121 S/cm at 900 °C). These results indicate the potential of Lu³⁺ as a dopant for enhancing the performance of ZrO₂ solid electrolytes.