A mixed-potential-type NO2 sensor based on a layered-structure Bi2W2O9 sensing electrode

Layered-structure Bi 2 W 2 O 9 powders synthesized by conventional solid-state reaction and treated by ball milling have been used to create an electrode for a mixed-potential-type NO 2 sensor with yttria-stabilized zirconia as an oxygen ion conductor. This sensor was found to provide good sensitivity to NO 2 at 500 °C, thanks to the grain refinement induced by ball milling. The electromotive force generated was linear to the logarithm of NO 2 concentration in the range of 30–500 ppm, with analysis of the impedance spectroscopy revealing a similar linear correlation between the conductance of the electrode and the logarithm of NO 2 concentration. The influence of CO 2 was also examined and found to have little effect on the sensitivity of the sensor.