High-temperature sensors for NO and NO2 based onstabilized zirconiaand spinel-type oxide electrodes

Zirconia-based electrochemical devices attached with an oxide sensing electrode have been examined for gas sensing properties towards NO and NO 2 at high temperature. Among the twelve kinds of spinel-type oxides tested, CdCr 2 O 4 was the most sensitive electrode material to both NO and NO 2 in air at 500–600 °C, also being endowed with quick response and recovery characteristics. Values of E EMF of the CdCr 2 O 4 -attached device decreased or increased linearly with an increase in the logarithm of NO or NO 2 concentration, respectively. The same device gave small or insignificant cross-sensitivities to H 2 , CO, CH 4 , CO 2 and H 2 O. Sensing mechanisms involving mixed potential were confirmed from the measurements of polarization curves.