Preparation Of SnO₂ Material And Study On Its Gas Sensing Properties

SnO2 is the most extensive application of gas-sensitive material as a wide bandgap semiconductor material. The purpose of this work is that preparing excellent capability of SnO2 gas-sensitive material. Preparing technical parameters and gas-sensitive characteristic were studied in the light of deeply understanding of current circumstances at home and abroad.SnO2 was prepared by sol-gel method successfully and the average grain-size is between 10 and 50 nm. We have observed the effects of citric acid's concentration, sintering temperature, adulterant on the structure and grain size, and the optimized technical parameters of prepared nano-SnO2 have been selected. Further more, colloid which was prepared by the method of sol-gel was used to make sensing sensors with pull plating film and according traditional and aside heating technics, sensing capability was studied, and sensing mechanism was discussed initiatively.Structure, component, size and appearance of crystal were characterized using XRD, TEM and so on. Analysis result indicate that the stabilization of colloid become better than before doping citric acid, and the influence of citric acid concentration is lesser relatively to the grain size of SnO2 films. The grain size of SnO2 obviously increases along with the sintering temperature rising. When the temperature is 400℃, there will be the smallest grain-size which is 23.2 nm. After doping Ce3+,Cu2+ and La3+ elements, crystal's growth was restrained. Along with the increase of adulteration, grain-size becomes small. This is mainly doping substances attached to the surface of SnO2 grain, so crystal's growth was restrained.Using static prepared gas, we have detected sensor's sensing character with an optimum heating voltage, and this time the gas molecules mainly give priority to chemisorption, gas in the material surface of ions present adsorption state, and the binding force between them, is mainly chemical bonding force. Pure SnO2 films which were treated at 400℃have the favorite sensitivity. Along with the increaseing of gas concentration, sensing characters improved obviously. After doping Ce, Cu and La, the activation energy of chemical adsorption was reduced, and the process of chemical reactions was speeded up. The sensitivities of sensors were improved effectively to ethanol, but optimized heating voltage rises. Prepared sensors have excellent sensitivity when doping Ce or Cu or La around 4%. Optimized sintering temperature is 500℃, and sensors have a better response for low- concentrated ethanol.