TAGUCHI-TYPE NOX GAS SENSORS BASED ON SEMICONDUCTING MIXED OXIDES

Mixtures of Al2O3-ZnO-V2O5 have been explored for use as active sensing materials in Taguchi-type NO, sensors. The electrical resistance and Seebeck effect of these semiconducting oxide mixtures have been measured as a function of the composition. The sensitivity and selectivity of the sensor to NO and NO2 gases against CO2 were studied in order to find the optimal composition of the oxides. The presence of p-n junctions may play an important role in the conductivity and sensitivity of the sensor materials. The experimental results indicate that sensors based on mixtures Of Al2O3-ZnO-V2O5 exhibit sensitive and fast response to 20 to 300 ppm of NO and/or NO2 in the temperature range of 200 to 400-degrees-C, the sensitivity to NO is usually larger than that to NO2. The sensors are almost insensitive to even 0.01 atm CO2 gas. A preliminary discussion on the operation principle of the sensors is presented.