Crystal Structure and Oxygen Ion Conductivity of Ga3 + Co-Doped Scandia-Stabilized Zirconia

The effect of gallium co-doping to scandia-stabilized zirconia (ScSZ) on the phase stabilization and ionic conductivity has been investigated. A series of samples (ZrO 2 ) 0.89 (SC 2 O 3 ) 0.11-x (Ga 2 O 3 ) x was prepared by sol-gel method and characterized the phase by X-ray diffraction. By substitution of 1-6 mol % Ga 3+ for Sc 3+ , the cubic phase of (ZrO 2 ) 0.89 (SC 2 O 3 ) 0.11 was stabilized at room temperature and the conductivity at lower temperature region was improved. The conductivity in the cubic phase moderately decreased with the increasing content of Ga 3+ in (ZrO 2 ) 0.89 (Sc 2 O 3 ) 0.11 Ga 2 O 3 ) x in all the temperature region examined. This decline in conductivity seems to be caused by the local structure change, which was detected by Raman scattering spectroscopy. From the temperature dependence of the electric conductivity, an ion migration activation enthalpy and the dopant ion-vacancy association enthalpy were estimated. By substitution of Ga 3+ for Sc 3+ , the association enthalpy steeply decreased, whereas the ion migration activation enthalpy gradually increased with increasing the Ga 3+ content.