Ionic conductivity and phase stabilization in zirconia-scandia-europia

Abstract

Zirconia-8 mol% yttria is widely used as electrolyte in solid oxide fuel cells, due to its high ionic conductivity and good mechanical and chemical properties. Nevertheless, scandia-stabilized zirconia is recognized as exhibiting the highest ionic conductivity among zirconia-based solid electrolytes. Stabilization of the high symmetry and high ionic conductivity cubic phase in this system is non-trivial. Introduction of a second additive (or dopant) is a usual strategy to overcome that constraint. In this work, europium oxide has been added to 10 mol% scandia-stabilized zirconia (10ScSZ) aiming full stabilization of the cubic structure at room temperature. The influence of europia addition (up to 1.25 mol%) on phase stabilization and ionic conductivity of 10ScSZ was investigated by differential scanning calorimetry and impedance spectroscopy. The higher is the fraction of europia into solid solution the lower is the temperature of the endothermic event due to phase transition. The cubic phase is fully stabilized at room temperature for 1 mol% europia addition. The grain and total ionic conductivity show typical Arrhenius behavior. The magnitude of the total conductivity increases with increasing europia addition.