Review—Metal Oxide Chemoresistive Gas Sensing Mechanism, Parameters, and Applications

Economic growth depends upon Micro, Small and Medium Enterprises (MSMEs) as they play a vital role in GDP and employment. Transportation is considered the lifeline of any country. In the last 10 years, ferrite-based sensors have been used primarily to detect harmful gases, pollutants from vehicle exhaust, and for environmental pollution monitoring. These soft ferrites have excellent electrical and magnetic properties that can be tuned to increase sensitivity and selectivity. The tuning of ferrite sensors depends upon synthesis technique, optimizing preparation conditions, sintering temperatures, operating temperatures, dopant concentration, etc. This paper is based on a deep study of the gas sensing mechanisms, parameters, and application of chemo-resistive metal oxide gas sensors. The key parameters for the ferrite gas sensors are phase formation, crystallite size, grain size, surface area, selectivity, dopants, sensitivity, gas concentration, operating temperature, response/recovery time. This review paper also includes the study of different researchers to find the impact of high concentration of gases like hydrogen, carbon monoxide, carbon dioxide , oxygen (O2), ethylene glycol 〖〖(CH〗_2 OH)〗_(2 ), methane (CH4), ammonia (NH3) liquid petroleum gas (LPG), acetylene (C2H2), and nitrogen oxides (NOx) in the environment and the metal oxide materials selected sensor applications.