Electrode materials, interface processes and transport properties of yttria-doped zirconia

The kinetics of the oxygen exchange reactions at the electrodes of a galvanic cell using yttria-doped zirconia single crystals (9.5 mole-% Y₂O₃) as solid electrolyte and Pt or Ag as electrode materials was studied by complex impedance spectroscopy. The electrode resistance when using silver was found to have negligible values over the temperature range 180 – 900 °C. In agreement with these results, oxygen sensors were tested successfully at temperatures as low as 200 °C. According to the performance of silver as electrode material, an electrochemical method was developed to determine the oxygen diffusion coefficient in doped zirconia. The results obtained, compared to those of conductivity and oxygen tracer diffusion measurements, have allowed us to obtain information both on the structure of the defects in yttria-doped zirconia and on the correlation factor. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997