High-temperature NOx sensors using zirconia solid electrolyte and zinc-family oxide sensing electrode

Abstract Yttria-stabilized zirconia (YSZ) electrochemical sensors attached with the zinc-family oxide (ZnFe 2 O 4 and ZnCr 2 O 4 ) sensing electrode (SE) were fabricated and examined for NOx sensing properties at high temperatures. These oxide-SE-attached devices gave a linear correlation between EMF and the logarithm of NO 2 (or NO) concentration from 50 to 436 ppm in the temperature range 600–700 °C. The sensor using the combination of ZnFe 2 O 4 and ZnCr 2 O 4 was found to give the highest sensitivity to NO 2 in air at 700 °C among the oxide-SEs tested and reported in the literatures to date. Furthermore, addition of Pt to ZnFe 2 O 4 was found to improve the sensing characteristics towards quick response. It was confirmed that the sensing performances to NO 2 were roughly related to those to O 2 for the devices tested here.