| Tin oxide is a n-type semiconductor with wide band gap of 3.6eV. Due to its unique photoelectric, catalyst and gas sensing properties, tin oxide has a broad application on several aspects, such as transparent conductive thin film, ceramics, sensors, lithium batteries, solar battery, catalyst, and optical technology, etc. especially in gas sensing field. As the Tin oxide has some characteristics of long life, high sensitivity, and low costs, the gas sensors we can find in the market is mainly made of tin oxide. But their sensitivity and selective are not ideal. Decreasing the size of the grain and doping metal are useful methods for improving the gas sensing property.In this paper, pure and SnO2 nanofiber doping metal successfully fabricated by electrospinning, and they were investigated by field emission scanning electron microscopy, X-ray Diffraction, Raman spectrum, photoluminescence spectrum and gas sensing tester. The results show that:1. The electrospinning progress is influenced by PVA concentration, voltage, sintering. etc. This paper systematically studies the affect of process parameters to the nanofibers. The results show that the diameter of the nanofiber decrease as the PVA concentration drops. When the PVA concentration is low, there appears pearls in the diameter of the nanofibers, They turn to liquid drop when the PVA concentration increases. The spinning voltage and the distance of electrode could directly affect the number of the liquid drops at the fiber felt surface, the diameter of the fiber and the speed of the spinning. The addition of the alcohol solvent makes the spinning easier.2. The structures with coarse surface and large specific surface are got by annealing and sintering to the SnO2 nanofibers made by electrospining. The SnO2 nanofibers are rutile structure with the lattice constants of 0.4737 and 0.3186nm for a and c respectively. Furthermore, it was found that the doping of a small amount of the metal elements such as Zn, Ag, Ni, and Mg do not change the crystal structure of the SnO2. But the annealing temperature has a great effect on the quality of crystallization. The higher of the sinter temperature, the higher quality of the crystallization. 3. The gas sensing property of the pure SnO2 and the metal-doped SnO2 nanobelts were also studied. The result shows that when the annealing temperature reaches to 700℃, the pure SnO2 nanofibers possess good gas sensing character and good selectivity to H2S and ethanol gas. However, their selective stability should be further improved. The doping of Ag raised the gas sensitivity of SnO2. When the concentration of Ag is 8at%, SnO2 nanobelts show excellent sensitivity to C2H2 gas. When the concentration of Zn reaches to 11at%, the nanobelt gas sensor behaves good gas sensing and selectivity to ethanol, toluene and acetylene at the temperature of 300℃,350℃and 200℃respectively. The SnO2 nanobelt sensor shows fine sensibility and selectivity especially for alcohol and toluol gases when the composition of the doped Ni is 8at%. The quality of crystallite of SnO2 is reduced by the corporation of Mg, but the nanofiber display improved selectivity and sensitivity when the concentration of Mg is 5at%. |
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