CAPACITIVE-TYPE SENSORS FOR THE SELECTIVE DETECTION OF NITROGEN-OXIDES

Since the capacitance of an oxide mixture consisting of two kinds of semiconducting oxides depends on the NO concentration, these mixed-oxide capacitors can be applied for a capacitive type of NOx sensor. Among the examined oxides, NiO mixed with ZnO was the most promising in terms of the sensitivity and response characteristics. A temperature slightly higher than 300 degrees C was desirable as the operating temperature of the NiO-ZnO element, and a linear relationship between capacitance and NOx concentration exists below 30 ppm, Furthermore, the capacitance of NiO-ZnO is highly selective to NOx As a result, the binary oxide of NiO-ZnO has a great potential as a new type of NOx sensor based on capacitance change.