Research On Gelcasting Process Of Indium Tin Oxide Cermics

Abstract:Indium tin oxide (ITO) ceramics is a heavily-doped n-type semiconductor, which is often used as the target in magnetron sputtering process to prepare ITO transparent conductive thin films. ITO target used in industry has the characteristics such ashigh density, high conductivity and homogeneous microstructure. However, the traditional productionprocesses. of ITO ceramic target have some defects such as high cost, difficulty to obtain large size, while gelcasting has the advantages such aslow cost and the ability to prepare devices with large size and even irregular shape. The raw material powderswidely used in the production of ITO ceramic target is usually nano-sized, and is not capableto prepare ceramic slurry, so it is necessary to explore the preparation of raw material powders.In this paper,a hydrothermal method was explored to prepare In2O3; aprocess which combined gelcasting and normal pressure sintering to prepare ITO ceramics was carried out, the properties of slurries prepared using ITO nano-powder and home-made In2O3/SnO2powder as raw materials respectively were anlyzed;the density of sintered bodies were also anlyzed. The main results are as follows:(1) The shape of In(OH)3prepared by hydrothermal method is cubic or tetragonal;the particle size decreases as the pH value increases, and increases with the reaction time is prolonged untill6h; the addition of surfactant in reaction can hlepto obtain uniform grains. With the condition that PH=7,1wt%polyethylene glycol (PEG), and12-hours160℃hydrothermal reaction,uniform In(OH)3cubeswith a size of100～300nm can be obtained. A near-spherical In2O3powder with a particle size of100-200nm can be obtained after calcination at600℃with a heating rate of5℃/min.(2) The viscosity of the slurry prepared with ITO nano-powder increases at first whenthe amount of ammonium polyacrylic (NH4PAA)increasesand then decreases with its content increasing, and the optimal amount of NH4PAA added is0.75wt%;the viscosity increases with solid loading increasing; the addion of acrylamide (AM) can reduce the viscosity. When conditions are pH=10, NH4PAA==0.75wt%, AM=15wt%, the solid laoding of the slurry can reach to40vol%and is still flowable;the density of body sintered at1580℃for8h is6.61g/cm3(when7.15g/cm3is set as theoretical density, the relative density is92.4%).(3) In2O3prepared by calcining the hydrothermal In(OH)3and nano SnO2was mixed at the mass ratio of9:1to obtain In2O3/SnO2composite powders. The viscosity of the slurry prepared with In2O3/SnO2powders increases at first when the amount of NH4PAA increasesthen tends to be almost stationary, and the optimal amount of NH4PAA added is1.5wt%; the viscosity increases with solid loading increasing; the addion of AM can reduce the viscosity. When conditions are pH=10, NH4PAA=1.5wt%, AM=15wt%, the solid laoding of the slurry can reach to45vol%and flows well;the density of body sintered at1580℃for8his7.01g/cm3(when7.15g/cm3is set as theoretical density, the relative density is98.1%).