Fabrication Of SnO₂ Thick-film Gas Sensor And In/Mg Material Modification

This paper introduced with the feature analysis of nanometer SnO2 powder which is made from tin powder, nitric acid and ammonia by adopting technical measures as XRD, SEM, etc. The XRD and SEM analyses demonstrate that the scale of SnO2 powder made through hydrothermal method is nanometer, and the average size of crystalline is 5 nanometers. Proceed with XRD testing on powders. With the different hydrothermal synthesis times of 3h﹑ 9h and 13h, the particle diameters of powders vary as 4.1nm, 4.4nm and 5.0nm.By making thick film gas sensors using different kinds of powder, furthering the analysis of thick film engineering process, this paper established that the agglomeration temperature of nano-powder is 300℃, the ratio of gas sensor powder to glass powder in the thick film mixed powder is 8:1, the ratio of ethyl cellulose to terpineol in organic bond is 1:15. This paper furthered the research by testing sensitivity, selectivity, stability, response and recovery time of sensors. Making gas sensors applied SnO2 powder from market with different thickness of films and testing gas sensor performance, this paper discussed the influence of film thickness on gas sensor performance and compared the gas sensors which applied SnO2 powder from market with those which applied SnO2 powder from hydrothermal nanometer SnO2 powder.Through many experiments, this paper researched on the method of making mixed powder of MgO-SnO2 and In2O3-SnO2 by hydrothermal approach, and established the engineering process of mixing and the thermal processing temperature of gas sensors. By a mass of gas sensitivity testing, this paper concluded that the gas sensors made from mixed powder with MgO can improve the gas absorbing ability of thick film gas sensors, reduce the response and recovery time, and slightly promote the sensitivity of gas sensor materials. The research on gas sensitivity performance on those made from mixed powder with In2O3 proved that the sensitivity performances of gas sensors can achieve the best when the ratio of In2O3 is 30wt%SnO2 nanometer powder. Under this condition, the sensitivity of gas sensors to 30ppm H2S is 366.7, the response time is 70s, the optimizing working concentration is 30ppm, and the optimizing working temperature range is 150℃～175℃.In the end, this paper concluded and put forward some issues in the process of research and furthered the future development of gas sensors.