Measurement of Ionic and Electronic Conductivities of Yttria-Stabilized Zirconia by an Embedded Electrode Method

A new technique is presented for the measurement of ionic and electronic conductivities in predominantly oxygen ion conducting materials such as 8YSZ. Cylindrical disc samples of 8YSZ with an embedded Pt wire electrode in the center and two surface porous Pt electrodes were fabricated. When a DC electrical potential is applied across one surface electrode and the embedded electrode, oxygen ions migrate through the YSZ toward the embedded electrode, while electrons transport in the external circuit. In this manner, neutral oxygen is electrochemically pumped to the embedded electrode raising the local oxygen chemical potential. Under the pressure built up, oxygen permeation occurs from the embedded electrode, through the YSZ sample, to the outer surfaces of the sample. In steady state, the electrochemical oxygen flux to the embedded electrode under applied voltage is exactly balanced by out permeation of oxygen governed by the electronic conductivity. Using this technique both the ionic and the electronic conductivities of YSZ were measured at a temperature as low as 500°C.