Selective sensing of oxidizing gases on Co-Ni-Zn ferrite: Mechanism and response characteristics

Abstract

Studies demonstrate the selective gas sensing characteristics of Co-Ni-Zn ferrite thick film towards oxidizing gases over reducing gases. The Co sub(0.3)Ni sub(0.3)Zn sub(0.4)Fe sub(2)O sub(4) ferrite was prepared by combustion method and characterized for its phase purity, nanodimension and valence state by analytical techniques, includes X-ray diffraction, Raman spectroscopy, Transmission Electron Microscopy and X-ray photoelectron spectroscopy, respectively. The Co sub(0.3)Ni sub(0.3)Zn sub(0.4)Fe sub(2)O sub(4) gas sensor was fabricated in the form of thick film by screen printing method, and the response of film towards selected oxidizing gases and the reducing gases were investigated. It was found that Co sub(0.3)Ni sub(0.3)Zn sub(0.4)Fe sub(2)O sub(4) thick film is highly active towards oxidizing gases at 200 degrees C, whereas almost negligible response was observed for reducing gases at all temperatures ranging from RT to 300 degrees C. The Oxygen adsorption - desorption mechanism is proposed for sensing of NO sub(2) and Cl sub(2) gases, and stated to be favored by n to p type conductivity transition on the surface of sensor film at 200 degrees C.