HIGH-TEMPERATURE SENSORS FOR NO AND NO2 BASED ON STABILIZED ZIRCONIA AND SPINEL-TYPE OXIDE ELECTRODES

Zirconia-based electrochemical devices attached with an oxide sensing electrode have been examined for gas sensing properties towards NO and NO2 at high temperature. Among the twelve kinds of spinel-type oxides tested, CdCr2O4 was the most sensitive electrode material to both NO and NO2 in air at 500-600 degrees C, also being endowed with quick res ponse and recovery characteristics. Values of E-EMF of the CdCr2O4-att ached device decreased or increased linearly with an increase in the l ogarithm of NO or NO2 concentration, respectively. The same device gav e small or insignificant cross-sensitivities to H-2, CO, CH4, CO2 and H2O. Sensing mechanisms involving mixed potential were confirmed from the measurements of polarization curves.