Extraction Of Microstructure Parameters For WO₃Porous Films And The Research On Its Selectivity To Monoaromatic Hydrocarbons

In recent years, the relationship of gas detection and people’s daily life is becomingmore and more closely, such as the detection of toxic and harmful gases in an indoorenvironment, the control of flammable and explosive gases in the industrial production,monitoring, and the monitoring of atmospheric pollution. Metal oxide semiconductor（MOS） gas sensor is a device which is capable of sensing the gas and its concentration inthe environment. The information of gas type and concentration are transformed intoelectrical signals. According to the intensity of the electrical signals and the responsivemode, the existing information of gas is obtained. Thus, the aim of detection, control,analysis and alarm is achieved. Compared with the other conventional gas analysis methodMOS gas sensor possesses many advantages, such as fast analysis, easy operation, simplestructure, conveniently carrying, low cost, high sensitivity, which result in the widely usedof it in the gas detection of food quality, environmental monitoring, industrial production,medical, aerospace, and so on.However, the practical application of MOS gas sensor is facing the problem of lowsensitivity and poor selectivity. The performance of the MOS gas sensor is largelydetermined by the property of gas sensitive material, while the property of gas sensitivematerial, to a large extent, is dependent on its microstructure. No matter the dopingmethod, or controlling the manufacturing process, the real purpose is to adjust themicrostructure of sensitive materials, thus changing the gas sensitive properties of material.Therefore, an important part of sensitive materials science is to find out the interrelatedmechanism between microstructure and sensitivity, selectivity, so as to control themicrostructure and improve the gas sensing properties.The conduction model of the structure and properties of materials is an effectivequantitative method to study the interrelated mechanism between microstructure and gassensing properties. In this paper, based on the conduction model for porous materialsproposed by our research group, the microstructure parameters were extracted by themulti-parameter fitting of I-V curves in different environments to study the relationshipbetween the microstructure parameters and sensitivity and selectivity. Furthermore, thefunction mechanism was explored. The paper mainly studied on the effect of sintering necks on the sensitivities of WO₃porous films, and the selective performances of WO₃tobenzene, toluene, xylene were also discussed.The experimental results showed that, different sintering temperatures resulted in thediverse contents of sintering neck. The sensitivity of material would be directly influencedby the content of sintering neck. The higher content of sintering neck brought about thebigger sensitivity. The sintering neck was divided into three categories: wide neck, narrowneck and closed neck, among them, narrow neck acting a switch role enhanced sensitiveapparently, while the enhancing of wide neck was smaller, and closed neck minimal. Thefurther gas sensitive test of WO₃sintered at600℃revealed that its response to benzenepresented obviously selective performance. This selectivity was attributed to chemicalstructure, such as the functional groups, of benzene, toluene and xylene. The WO₃gassensor has the application prospect in the detection of monoaromatic hydrocarbons.