Oxygen vacancies contributing to intragranular electrical conduction of yttria-stabilized zirconia (YSZ) ceramics

Abstract

The behaviors of oxygen vacancies, which dominate electrical conduction within the grains of Zr 0.85Y 0.15O 2 − δ (non-doped YSZ) ceramics, were investigated by dielectric measurements as a function of temperature. Trials were carried out to identify the trapping center for oxygen vacancies at low temperatures by partially substituting Hf 4+ or Sc 3+ for Zr 4+ or Y 3+ (doped YSZ). The bulk resistance obtained by impedance analysis and the relaxation process of the dielectric loss tangent yield estimates of the migration energy of O 2− ion, E M, and the dissociation energy required to extricate an oxygen vacancy from the trapped state, E O. The dielectric results for doped YSZ suggest that the excess oxygen vacancies are preferentially bound to Zr 4+ rather than Y 3+ in non-doped YSZ. In Zr 0.85Y 0.15O 2 − δ , intragranular electrical conduction results from O 2− migrations with E M = 1.01 ± 0.02 eV, which require the assistance of free mobile oxygen vacancies that are thermally dissociated from their bound state by Zr 4+ with E O = 50 ± 1 meV.