Effect of TiO2 Addition on Phase Stability and Electrical Conductivity of Cubic Zirconia Used as an Electrolyte in Solid Oxide Fuel Cells

Abstract

The influence of TiO2 addition on the phase stability and electrical conductivity of cubic zirconia was studied. XRD results showed that when the TiO2 amount was less than 5 wt %, the specimens were entirely in single cubic phase; further addition of TiO2 destabilized cubic zirconia phase and caused the formation of tetragonal phase. The amount of tetragonal phase increased with increasing TiO2 content in cubic zirconia matrix. The electrical conductivity of the specimens was measured using a frequency response analyzer in the frequency range of 5-13 MHz in air and in the temperature range of 300-800 oC. It was seen that the electrical conductivity of the TiO2 doped cubic zirconia decreased with increasing TiO2 content. This decrease was due to both a trapping of the oxygen ion vacancies at Ti ions and the formation of tetragonal phase which gives rise to a reduction in moving oxygen vacancies.