Study On Properties Of Nanocrystalline Tin Oxide Thick-film Gas Sensor For H₂S

Nanocrystalline sensors have attracted great research interests due to their excellent and unique sensing properties such as high sensitivity, high selectivity and quick recover/response. Hydrogen sulfide (H2S) gas sensor has important application in industrial areas such as oil, natural gases exploitation and coal manufacturing. In this study, a type of thick-film gas sensor has been developed through screen printing method with tin oxide nanoparticles. The addition of CuO is adopted to increase the selectivity toward H2S.The fabrication of SnO2 nanoparticles through the polymer-network technique and hydrothermal method was firstly studied, and the best conditions were defined by investigation and the analysis of XRD,SEM and TEM. Meanwhile, the particle size of the SnO2 nanoparticles made on the best conditions was measured. The experiment results show that the average crystalline size of SnO2 particles obtained is below 30 nanometers. Both the nanoparticles are spherical, uniform, and well-dispersed. The investigation of fabricating nanocrystalline CuO-SnO2 thick films by the screen-printing method is introduced. In this process, hydrothermal method was used to synthesize CuO doped tin oxide nanoparticles, which was mixed with glass frit, antimony trioxide and organic vehicle to form a paste with suitable viscosity. The paste was printed on alumina substrates and then leveled at room temperature. The printed thick film samples were dried in air and sintered to obtain sufficient mechanical strength. The morphology and crystallinity of the CuO-SnO2 thick-films with different CuO doping percentage was characterized and the sensing characteristics were investigated in a vacuum chamber for H2S gas at different temperature. The results show that the particles of CuO-SnO2 thick-film are spherical and have a narrow size distribution typically below 50 nanometers. The CuO-SnO2 thick-film was highly porous and has many channels, which helps to improve the sensitivity towards H2S gas. The gas sensing element has the best performance when doping 3 wt% CuO. The gas sensitivity is 219.63 to 100 ppm H2S at 200°C, and the selectivity towards CH4 and CO is perfect. This kind of CuO-SnO2 thick-film also has good sensitivity to low consentration H2S gas at room temperature (25°C).