High-temperature sensors for NO and NO2 based on stabilized zirconiaand spinel-type oxide electrodes

Abstract

Zirconia-based electrochemical devices attached with an oxide sensing electrode have been examined for gas sensing properties towards NO and NO ₂ at high temperature. Among the twelve kinds of spinel-type oxides tested, CdCr ₂ O ₄ was the most sensitive electrode material to both NO and NO ₂ in air at 500–600 °C, also being endowed with quick response and recovery characteristics. Values of E _EMF of the CdCr ₂ O ₄ -attached device decreased or increased linearly with an increase in the logarithm of NO or NO ₂ concentration, respectively. The same device gave small or insignificant cross-sensitivities to H ₂ , CO, CH ₄ , CO ₂ and H ₂ O. Sensing mechanisms involving mixed potential were confirmed from the measurements of polarization curves.