NO2 Sensor Using Sc2O3-ZrO2 Solid Electrolyte and CuO + CuCr2O4 Sensing Electrode

Solid-state planar NO2 sensor using scandia-stabilised zirconia (8mol%Sc2O3-ZrO2) solid electrolyte and seven different oxide sensing electrodes have been tested in NO2 containing gaseous atmosphere in the range of 10 ppm to 500 ppm NO2 between 520 oC to 660 oC. Among the sensors incorporating seven different kinds of oxide sensing electrode, the sensor with CuO + CuCr2O4 mixed-oxide electrode has been found to respond consistently and rapidly to change in concentration of NO2 in the oxygen rich gas mixture at 660 ºC. A logarithmic relationship between the measured electromotive force (EMF) and NO2 concentration from 100 to 500 ppm has been observed at 660 ºC whereas a linear relationship between EMF and NO2 concentration has been observed below 30 ppm at the same temperature of measurement. The sensor exhibited negligible cross-sensitivity to CO and CH4 in the gas stream at 660 oC. A possible sensing mechanism has been discussed.