Electrical properties of ZrO₂-CeO₂ at intermediate temperatures

Both ZrO₂-CeO₂ powder materials and thin film ceramic membranes have been prepared by sol-gel processes. Sol and suspensoid were used as dips for preparing the thin film membranes in this work. The membranes, with a thickness in the range of 200 nm to a few mm, were coated on porous alumina ceramic substrates by a slip-coating or spin-coating process for different purposes. The ZrO₂-CeO₂ thin film membranes are highly conductive and transparent with an ionic conductivity as high as 10^-2 S/cm at 600° which is two orders of magnitude higher than that of the bulk materials. This is perhaps caused by a different microstructure for the thin film membranes compared to the bulk materials. The thin films, but not the bulk samples, are stable in reduced atmosphere. By controlling the composition and atmosphere, the ZrO₂-CeO₂ materials can be ionic, electronic or mixed conductors. For the bulk samples a transition has been observed where the conductivity increases by about two orders of magnitude.