Development of NO sensing devices based on YSZ and oxide electrode aiming for monitoring car exhausts

Abstract Recent progress in the development of zirconia-based sensing devices using zinc-family oxide electrodes for both mixed-potential and complex impedance-based types has been focused on the detection of NO x in the temperature range of 600–700 °C. The sensing characteristics of these sensors were investigated in different gaseous environments. The mixed-potential-type NO x sensor using ZnFe 2 O 4 sensing electrode (SE) have shown the highest sensitivity to NO x among other spinel-type oxides tested as SEs in the temperature range of 600–700 °C. It was also shown that the complex-impedance-based NO x sensor attached with ZnCr 2 O 4 -SE gave rather good sensing characteristics to NO x at 700 °C. Furthermore, it was discovered that the sensitivity to NO is almost equal to the sensitivity to NO 2 from 0 to 200 ppm for this sensor at 700 °C. The observed NO x sensitivity and the measured NO x concentration had almost linear correlation even in the presence of 8 vol.% H 2 O and 15 vol.% CO 2 . Based on the results obtained, we proposed laminated-type sensor structure that is the best for the present complex impedance-based NO x sensor.