An investigation of phase stability and electrical conductivity of TiO2 doped cubic zirkonia used as an electrolyte material in solid oxide fuel cells

AN INVESTIGATION OF PHASE STABILITY AND ELECTRICALCONDUCTIVITY OF TiO2 DOPED CUBIC ZIRKONIA USED AS ANELECTROLYTE MATERIAL IN SOLID OXIDE FUEL CELLS(M.Sc. Thesis)Ali AKÇ MENGAZ UNIVERSITYINSTITUTE OF SCIENCE AND TECHNOLOGYSeptember 2006ABSTRACTThe influence of TiO2 addition on the phase stability, microstructureand electrical conductivity of cubic zirconia was studied. Specimenscontaining TiO2 addition up to 10 wt% were produced by colloidalprocessing and pressureless sintering. XRD results showed that whenthe TiO2 amount was less than 5 wt %, the specimens were entirely insingle cubic phase; further addition of TiO2 (5 wt% or more)destabilized cubic zirconia phase and caused the formation oftetragonal phase. Also, the amount of tetragonal phase increased withincreasing TiO2 content in cubic zirconia matrix. The electricalconductivity of the specimens was measured using a frequencyresponse analyzer in the frequency range of 5-13 MHz in air and in thetemperature range of 300-800 oC. The experimental results showed thatthe conductivity increased with increasing temperature at constant TiO2amount. This increase was mainly a result of the increased grain sizeand the consequent reduction in the total grain boundary area. Also,the electrical conductivity decreased with increasing TiO2 content. Thisdecrease was due to both a trapping of the oxygen ion vacancies at Tiions and the formation of tetragonal phase which gives rise to areduction in moving oxygen vacancies.: 710-703.1092Science CodeKey Words : Cubic Zirkonia, TiO2, Microstructure, LatticeParameter, Electrical ConductivitiyPage Number : 66Adviser : Prof.Dr. Süleyman TEKEL