Direct Preparation of Nonagglomerated Indium Tin Oxide Nanoparticles using Various Spray Pyrolysis Methods
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Indium tin oxide particles were prepared using three different spray synthetic techniques: conventional, salt-assisted, and low pressure. Optimum conditions for the preparation of small size, nonagglomerated particles were investigated for these three methods. The use of the conventional spray pyrolysis method resulted in only larger particles (submicrometer order). Salt-assisted spray pyrolysis (SASP) and low-pressure spray pyrolysis (LPSP) produced highly crystalline, dense, homogeneous, and nearly nonagglomerated nanoparticles that were less than 25 nm in size. The size of the particles was in the range 12–24 nm for the SASP method and 8–14 nm for the LPSP method. In addition, the LPSP method led to the production of single nanometer-size multicomponent particles in a single step with less heating time without the need for any post heat treatment and additives.
I. INTRODUCTION
Indium Tin Oxide (ITO) has extensively been studied because of its properties that include a low resistivity (10−4 ⍀ · cm) and high transparency to visible light.1,2 Both thick and thin ITO films are used in optelectronic, electroluminescent, electrochromic, and biological devices, photovoltaic cells, liquid crystal and flat panel displays, sensors, storage-type cathode ray tubes, and heat reflecting mirrors. Conventional methods for the preparation of ITO films, including vacuum and electron beam evaporation, radio frequency and direct current sputtering, pulsed laser ablation, and chemical vapor deposition are costly and require complex equipment and procedures. In general, ITO thin films produced by the above methods are polycrystalline with a grain size in the range of 10–100 nm, depending on the specific method used and the processing steps involved.3 Nanoparticles and nanostructured materials composed of metals and semiconductors whose exhibit sizedependent optical, magnetic, electronic, and catalytic properties have recently been heralded as the next generation of electronic devices in the design of advanced materials. It is well known that an agglomerate-free and highly crystalline particle with a narrow size distribution is required for the manufacture of reliable devices.
a)
Permanent address: Department of Physics, Bandung Institute of Technology, Jalan Ganeca 10, Bandung 40132, Indonesia. b) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2004.0141 J. Mater. Res., Vol. 19, No. 4, Apr 2004
Several routes for the synthesis of ITO particles, including coprecipitation,4 emulsion,5 sol-gel,6 and hydrothermal7,8 techniques have been reported. Hydrothermal processing and related liquid phase methods are used for the commercial preparation of fine and homogeneous particles with a low cost and ease of production. The disadvantages of these processes, however, include a nonhomogeneous chemical composition, strong agglomeration, a rather poor morphology, and low crystallinity. In addition to this, several hours are required to produce homogeneous and highly crystalline particles.4,8 It is
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