Sensing Characteristics of YSZ-Based Mixed-Potential-Type Planar NO[sub x] Sensors Using NiO Sensing Electrodes Sintered at Different Temperatures

The correlation between the sintering temperature and the sensing performances of the planar mixed-potential-type yttria-stabilized zirconia (YSZ)-based sensor attached with NiO sensing electrode (SE) was studied by materials characterization techniques, such as impedance analysis, polarization analysis, scanning electron microscopy, and transmission electron microscopy. The sensing properties of the planar YSZ-based sensors were investigated in the operating temperature range of 700-900°C. The sensitivity of the present sensor was found to be modulated by changing the sintering temperature of NiO-SE. Rather large sensitivity (43 mV) to 100 ppm was obtained even at 800°C for the sensor using the NiO-SE sintered at 1400°C. A sensing mechanism that involves mixed potential at SE as well as catalysis in gas-phase reaction was discussed based on the results obtained.