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

Layered-structure Bi₂W₂O₉ powders synthesized by conventional solid-state reaction and treated by ball milling have been used to create an electrode for a mixed-potential-type NO₂ sensor with yttria-stabilized zirconia as an oxygen ion conductor. This sensor was found to provide good sensitivity to NO₂ at 500 °C, thanks to the grain refinement induced by ball milling. The electromotive force generated was linear to the logarithm of NO₂ 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 NO₂ concentration. The influence of CO₂ was also examined and found to have little effect on the sensitivity of the sensor.