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Stabilization of sensing performance for mixed-potential-type zirconia-based hydrocarbon sensor

Fujio, Yuki, Plashnitsa, Vladimir V., Elumalai, Perumal, Miura, Norio
Talanta 2011 v.85 no.1 pp. 575-581
carbon dioxide, carbon monoxide, ceramics, electrodes, hydrogen, methane, nitric oxide, nitrogen dioxide, oxygen, scanning electron microscopy, water, water vapor
The recently reported sensing characteristics of the mixed-potential-type yttria-stabilized zirconia (YSZ)-based hydrocarbon (HC) sensor attached with ZnCr₂O₄-sensing electrode (SE) were found to be changed after the 10-day operation at 550°C under the wet condition (5vol.% water vapor). To improve the stability of the present sensor, the several modifications of the SE material by adding YSZ powder were examined. As a result, the sensor using the laminated (ZnCr₂O₄/YSZ)-SE gave the stable electromotive force (emf) response against 100ppm C₃H₆ at 550°C for about one month examined. Based on the scanning electron microscopy (SEM) observation and the AC complex-impedance measurements, it was concluded that the stable behavior of the sensor using the laminated (ZnCr₂O₄/YSZ)-SE was provided by the stabilization of the interface between ZnCr₂O₄ grains and YSZ particles. The fabricated sensor exhibited the linear dependence of sensitivity on the logarithm of either C₃H₆ concentration (in the range of 20–800ppm) or mixtures of various hydrocarbons (HCs) (in the range of 90–2600ppmC). In addition, the emf response was not altered by the change of O₂ (2–20vol.%), H₂O (0–10.8vol.%) and CO₂ (0–20vol.%) concentrations, and no interference of other gases (CO, NO, NO₂, H₂, and CH₄) was observed.