Non-Nernstian Planar Sensors Based on YSZ with Ta (10 at.%)-Doped Nanosized Titania as a Sensing Electrode for High-Temperature Applications

Planar sensors based on tape-cast YSZ layers with two parallel Pt (or Au) finger electrodes, one covered with Ta (10at.%)-doped nanosized titania powders, were prepared and studied. The sensors were tested at various concentrations of NO2, CO, and different hydrocarbons in the 450-650°C temperature range. The sensitivity to different target gases was found to be strongly dependent on the operating temperature. The replacement of Pt electrodes with Au was effective in promoting the response to propylene. Moreover, an inversion of the polarity of the electromotive force response to NO2 gas was observed in comparison with Pt-based sensors. The sensing mechanism is discussed. © 2006 The American Ceramic Society.