Chemical modifications of au-electrodes on YSZ and their influence on the non-Nernstian behaviour

The interface between gold electrodes and the solid electrolyte Zr_0.86Y_0.14O_1.93 (YSZ) was chemically modified in several ways. Nb₂O₅ was obtained in two states: as an X-ray amorphous surface layer after vacuum evaporation and dissolved in YSZ after annealing at 1150 °C. This was confirmed by X-ray diffraction with grazing incidence and Bragg-Brentano technique. On the metal side the modification was made by potentiostatic deposition of the electronically conducting perovskite La_1-xSr_xCrO₃ and subsequent annealing at 1000 °C. The influence of these modifications on the electrode potential in gases containing oxygen and propylene at temperatures ≤700 °C was investigated. The known sensitivity of the Au electrode to propylene is nearly maintained after both Nb₂O₅ modifications of the solid electrolyte. After modification with the chromite layer, the sensitivity to propylene disappeared completely in gas mixtures with excess oxygen. Strong differences in the sensitivity caused by chemical modifications can possibly be utilized in hydrocarbon sensors. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996