NOx sensors based on interfacing yttria stabilized zirconia with p and n-type semiconducting oxides

Electrochemical NOx sensors based on coupling yttria stabilized zirconia (YSZ), an oxygen-ion conductor, with different semiconducting oxides as auxiliary phase were studied. Nanosized LaFeO3 perovskite-type oxide, a p-type semiconductor, and n-type WO3 were used as auxiliary phases because of their NO2 sensing properties in resistive-type devices. LaFeO3 or WO3 thick films were deposited using a screen printing oil on one side of the solid-electrolyte pellets. The sensors were fully exposed to the same atmosphere. Electromotive force (EMF), polarization curves, amperometric and electrochemical impedance spectroscopy (EIS) measurements, were performed in air and at different concentrations of NO2 in air, at selected temperatures