Influence of yttria and ytterbia doping on phase stability and ionic conductivity of ScSZ solid electrolytes

In this paper the effect of scandia-stabilized zirconia solid electrolytes doping with yttria and ytterbia on phase stability and ionic conductivity of the material is studied. The novelty of the research lies in replacing part of scandia with an unequal amount of yttria or ytterbia, unlike most of previously reported studies, where amount of introduced dopant was equal to amount of removed scandia. It is shown that in composition with 8 mol% Sc2O3 + 1.6 mol% M2O3 and 6 mol% Sc2O3 + 3.2 mol% M2O3 the phase transformation of cubic zirconia to rhombohedral phase is completely suppressed. However, decrease in ionic conductivity in 500 °C–900 °C range in comparison with 10 mol% scandia composition is observed. The drop is attributed to decrease in concentration of oxygen vacancies and to increased migration enthalpy as calculated from the Arrhenius plots. It was also discovered that such doping reduces association enthalpy for oxygen vacancy—dopant cation complexes.