The Research On SnO₂ Gas Sensor

Nanometer SnO₂ powders were prepared by hydrothermal synthesis method. Methane gas sensor was fabricated with the powders and doped with Pd, Sb, Y on the base of the sensor. Hydrogen gas sensor was fabricated with the powders and doped with Ag, Al, Bi on the base of the sensor. The surface active material was composed of Al₂O₃ and Pt. Then the surface catalyst layer was fabricated with the materials by the surface catalyzing. Gas-sensing characteristics were tested in the different gas, such as methane, hydrogen and ethanol. The result was studied.The Nanometer SnO₂ powders were studied by SEM and X-ray diffraction instrument. Through the SEM photograph and XRD pattern, we can study the effect of chemical dynamic condition on the SnO₂ crystallite. The optimum temperature, time and pH value were 160℃,12h and 1.5.The effect of some catalysts on the thick film gas sensors was studied .We can find after we added Sb³⁺ ions to the hydrothermal SnO₂ crystallite, Sb³⁺ and Sb⁵⁺ exist on the SnO₂ crystallite. The shape had an effect on the SnO₂ crystallite structure, initialized resistance value and gas-sensing characteristics. After Pd catalyst was heat treatment, nanometer PdO_1-x dispersed in the surface of nanostructure thick film material. Spillover effect was investigated. Ag⁺ can exist on the surface of SnO₂ crystallite and substitute the Sn⁴⁺. The result was researched. In addition to that, the function of Y, Al, Bi had been studied.The gas sensor with coating of Al₂O₃ and H₂PtCl ? 6H₂O has high selectivity to interfered gas. Through the SEM photograph, we found the SnO₂ crystallite grain was like the puncheon and a porous net microstructure was formed. Then, we deduced the reaction process of different gas.Improving the selectivity of hydrogen gas sensor to ethanol is the difficult problem .It will be focused on studying in the future.