Studies On The Catalytic Property And Sensing Mechanism Of Indium Oxide Based Gas Sensing Material

Gas sensor is a kind of sensor that detects the target gas in the atmosphere, for it can induct the physical and chemical property of the target gases rapidly, and transform the chemical signal into electrical signal. Semiconductor gas sensor is popularly used for the detection of inflammable and toxic gases, because it has high sensitivity, low cost and mature technology. Indium oxide is a new gas sensing material, which can be expected to improve the selectivity, stability and decrease the power consumption of conventional sensing material. On the other hand, the research of gas sensing mechanism has lagged behind the application of gas sensor, so it is difficult to guide the design and development of gas sensing material. At the same time, gas-sensing mechanism of indium oxide is seldom reported. For the reasons above, the relationship between catalytic property and gas sensing performance has been established in this paper and the mechanism of indium oxide has been revealed firstly.The catalytic property of different grain size indium oxide to iso-butane and alcohol has been evaluated systematically by micro-reactor and gas chromatography; at the same time, gas-sensing property of the same material to iso-butane and alcohol has also been evaluated systematically by testing apparatus about gas sensing performance. The results show that the catalytic property and gas sensing performance of nanometer material are higher than that of common material; both of them are improved greatly with the decrease of grain size. It also shows that gas-sensing property is closely related to the catalytic property.The catalytic property of indium oxide with dopant to iso-butane and alcohol has been evaluated systematically; At the same time, gas sensing property of the same material to iso-butane and alcohol has also been evaluated systematically. The results show that the sensitivity of indium oxide doping noble metal to iso-butane is increased, for the dopant can improve the catalytic property of indium oxide; the sensitivity of indium oxide doping basic oxide(e.g.La203) to alcohol is increased andthe sensitivity to iso-butane is decreased, because these material can improve the catalytic property to alcohol and decrease the catalytic property to iso-butane. In the light of the research above, the conclusion that doping basic metal oxide can improve the sensitivity and selectivity to alcohol can be drew.Aging procedure is a necessary process of gas sensor fabrication, but the reason of this phenomena has not been reported; The catalytic and sensitivity property to alcohol during the aging procedure has also been investigated. The research shows that both of them are improved step by step with the increase of aging time and achieved a stable status in seven days. It also shows that the change of sensitivity is caused by the change of catalytic performance, and the gas-sensing performance is intrinsically depended on the catalytic performance.Catalytic property is close related to the sensing property. If the catalytic oxidation activity and reaction velocity are too small, the interaction of the sensing layer with the gas becomes too weak to generate strong response, so the sensitivity is small too. If the catalytic activity is too high, target gas or its reaction intermediates are consumed out at the surface region of gas sensing layer, being unable to induce a change in electrical resistance. Thus, the sensitivity becomes optimum when the element has an appropriate catalytic activity.