Research On Preparation Of Doped Tin Oxide Nano-powder(FTO) And Electric Properties

Wide band-gap material is one of the popular materials researched in recent years. SnO₂ is a wide-band oxide semiconductor with a bandwidth of 3.6⁴.0eV and a tetragonal rutile crystal structure. When SnO₂ doped with F, it has excellent properties, wide-band gap, high transparency in visible region, low resistivity and high stability. F-doped tin oxide(FTO) has been widely used in many fields such as solar cells, electric heating devices, transparen electrodes, and gas sensors, etc. Several methods are used in preparation of FTO, which include chemical vapour deposition (CVD), sputtering, thermal evaporation and sol-gel technique.Now, the syntheses of FTO films are usually reported and few reports discuss the preparation of powder. The Sb-doped tin oxide (ATO) powder, which has similar function with FTO, has been broadly studied. After being added impregnent and colophony, the ATO nano-powder can be used as anti-eletrostatic material and be widely used to coat, chemical fibre, paper making, wrappage, arthetecture material. But, there are few reports about the production of F-doped tin oxide powder. Due to the little difference between the F atom radius(0.133nm) and O atom radius(0.132nm), the doped F has little influence to the SnO₂ crystall lattice. The color of the FTO powder is celandine green and with a good dispersion, its transparence should be higher to the blue-colored ATO. So, the FTO nano-powder has a wide applied foreground. This paper introduce many preparation methods of Tin oxide films and powder, basic properties of undoped and doped tin oxide and its application in many areas. The F doped SnO₂ (FTO) nano-powder was successful synthesized with SnCl₂ and HF as raw material by wet-chemical method. After evaporating at 200°C and heating at 400°C, the Sn²⁺of the mixture is oxidated to Sn⁴⁺ and the F is doped in SnO₂. The effect of proportion of F to FTO powder and electric properties were discussed by XRD, SEM, and EDS, pressing flake method. The XRD result shows that the doping of F have not changed the SnO₂ tetragonal rutile crystal structure, and the intermediat product is SnO and the doping process occur in the oxidation process of SnO to SnO₂. The SEM results show that the FTO powder is flake figure, its magnitude is 50¹00nm and the thickness is 10²0nm. The powder has good dispersion and legible adumbration. But, with the doped-F contentincreased, the agglomeration trend increased. The EDS result shows that the composition of FTO powder is close to the previous proportion of raw materials. The resistivity test result shows that FTO nano-powder has a good electrical property (R <200Q/cm), which is lower to the ATO powder (prepared by same lab) and pure SnO2 powder. When the proportion of [Sn] to [Fn] is 10: 3, the FTO powder has lowest resistivity of 57.25Q/cm.