英文原文Synthesis of nano-sized antimony-doped tin oxide (ATO) particles using a DC arc plasma jetKeywords: Thermal plasma Antimony-doped tin oxide (ATO) NanopowderAbstrct Nano-sized antimony-doped tin oxide (ATO) particles were synthesized using DC arc plasma jet. The precursors SnCl4 and SbCl5 were injected into the plasma flame in the vapor phase. ATO powder could conveniently be synthesized without any other post-treatment in this study. To control the doping amount of antimony in the ATO particles, the Sb/Sn molar ratio was used as an operating variable. To study the effect of carrier gas on the particle size, argon and oxygen gases were used. The results of XRD and TGA show that all Sb ions penetrated the SnO2 lattice to substitute Sn ions. With the increased SbCl5 concentration in source material, the Sb doping level was also increased. The size of the particles synthesized using the argon carrier gas was much smaller than that of the particles prepared using the oxygen carrier gas. For the argon gas, PSA results and SEM images reveal that the average particle size was 19 nm. However, for the oxygen gas, the average particle size was 31 nm.1. IntroductionSnO2 is a typical wide band gap semiconductor and its conductivity is generally realized by non-stoichiometry associated with oxygen vacancies in the SnO2 lattice . However, the content of oxygen vacancies in SnO2 istypically difficult to control. Tin oxide doped with Sb, Mo, and F has been studied in the past due to the unique properties of the doped tin oxide such as preferable conductivity and transparency in visible light wavelength range . In particular, Sb is considered the best dopant due to its stability. Antimony-doped tin oxide (ATO) is an n-type semiconductor with electrons in the tin 5-based conduction band provided by the antimony dopant . The conductivity and transparency can be controlled by varying the amount of Sb dopant instead of by manipulating the non-stoichiometry.ATO has been studied in the past to measure its properties of the inherent electrochromism as well as its capacity for use in charge storage and as a catalyst . At low Sb doping level, ATO has properties of transparency at the visible region with good conductivity, while reflecting infrared light. These characteristics enable ATO to be used as a transparent electrode for electrochemical devices , displays , and heat mirrors and energy storage devices . Heavily doped ATO is a good catalyst for the oxidation of phenol and olefin and the dehydrogenation and ammoxidation of alkenes .Thus far, ATO particles have been mainly synthesized by solid and liquid state reaction method, such as solid state reaction , coprecipitation , a hydrothermal method , and a solgel method . Although solid and liquid state reactions are considered suitable methods to synthesize ATO nanopowder, these approaches require a large quantity of solution and organic materials, longer processing time, heat treatment for crystallization,filtration, and drying process. To overcome these weak points, in the present work we introduce a thermal plasma process to synthesize ATO nanopowders. The thermal plasma process has unique characteristics for the preparation of nanopowders as it involves high temperature and a quenching system .In this paper, nano-sized ATO powders were synthesized by an argon plasma jet at atmospheric pressure. To control the doping amount of ATO, different Sb/Sn molar ratios were applied. The effects of the Sb dopant on the phase composition and particle size have been discussed.2. ExperimentalNano-sized ATO was synthesized using an argon plasma jet atatmospheric pressure. Precursors were tin (IV) chloride (SnCl4,99.9%, Aldrich Co.) and antimony pentachloride (SbCl5, 99%,AldrichCo.). Because SnCl4 and SbCl5 easily evaporate at room temperatureand pressure, they were injected into the plasma flame in a vaporFig. 1. Schematic diagram of DC plasma jet for synthesis of ATO nanopowders.Table 1Experimental conditions for synthesis of nano-sized powderPlasma power300A, 6.9 kWPlasma gasAr: 15 l/minPressure750 TorrDuration of experiment10 minSource materialsTin (VI) chloride (99.9%, Aldrich Co.), feed rate: 0.41 g/min (carrier gas: Ar 2 l/min) Antimony pentachloride (99%, Aldrich Co.),feed rate: 0.076 g/min (carrier gas: Ar 2 l/min)phase without additional heating. Fig. 1 shows a schematic diagram of the DC plasma system. The source material was injected into the plasma flame through a bubbler by carrier gases of Ar and O2. The carrier gas flow rate for injection of the source materials was maintained at 2 l/min. The concentration of SbCl5 in the source materialwas varied in order to control themolar ratio of SbCl5/SnCl4 from 0.27 to 1.40. The experimental conditions and operating variables are summarized in Tables 1 and 2.Synthesized powder was collected at the reaction tube wall. These phase compositions of powd