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.