ELECTRICAL-CONDUCTIVITY AND POINT-DEFECT BEHAVIOR IN CERIA-STABILIZED ZIRCONIA

Ceria-stabilized zirconia has tremendous potential as a thermal barrier coating in gas turbines and as a fuel cell material. Unlike most stabilized-zirconia systems which are ionic conductors, ceria-doped zirconia has exhibited large electronic contributions at moderate temperatures and oxygen activities. The focus of this research has been to characterize this mixed conduction behavior. Electrical conductivity measurements have been performed as a function of composition, temperature and oxygen partial pressures. At high oxygen activities, oxygen vacancies are the dominant charge carriers while at lower oxygen partial pressures an electron hopping mechanism dominates. Reduced cerium ions and Ce3+-oxygen vacancy associates generate these conducting electrons. Kroger-Vink diagrams have been constructed which detail these mechanisms and describe the point defect behavior for ceria-stabilized zirconia.