Preparation And Process Optimization Of Highly Dense ITO Target

Indium tin oxide (ITO) target is a metal oxide composite material of mixing oxide tin and oxide indium, the ITO films prepared by ITO target have many advantages, such as low resistivity, high visible light transmittance, high absorption rate to ultraviolet, good wear and corrosion resistance and so on, because of these properties, ITO films are widely used into optoelectronic field. The ITO target preparation technology in our country is still at the primary stage, the performance of ITO target prepared in our country is low, it is difficult to meet the requirements of high-end products, and our country had to dependence on foreign imports long range, this situation had seriously hindered the establishment of information industry chain and the development of information industry to the high-end. It is great significance to develop preparation technology of high performance ITO target. The ITO target preparation methods mainly include atmosphere sintering, hot isostatic pressing, hot pressing and spark plasma sintering, because of the ITO target with high quality and large size, the atmosphere sintering method has become the main object of study in research institutes and manufacture.The technological process of ITO target prepared by sintering as the main line, the preparation process of pre treatment of nanometer ITO powder, ITO biscuit preparation and sintered ITO target were studied detailedly, the related performance of powders, biscuit and target are analyzed by SEM, XRD, solid density meter and TGA-DTA. The cylindrical ITO target with low resistivity and high density (higher than99.5%) were obtained. The effect of technology parameters on the performance of ITO granulation powder, ITO biscuit and ITO target were considered. Specifically as follows:(1) The parameters of centrifugal spray granulation process were optimized by orthogonal test, the effect of solid loading and binder content, rotation rate of spray head and drying temperature on the morphology, flow rate, packing density of the spray dried granules were examined, and the results show that the optimal operation parameters are obtained to prepare high spherical particles and uniform size distribution:solid content of slurry is50%, the binder concentration is1%and the rotation frequency of spray head is 10800r/min, the trying temperature of kiln is200℃, the packing densities and flow rate up to1.6123g/cm3and3.51s respectively; the effect of solid content on ITO granulation powder morphology is notable, the powder is steel pit and fragmentation when granulated with low solid content, it is not propitious for making ITO biscuit.(2) The influences of ultrasonic assisted molding processing parameters on the density and microstructure of the ITO green compact are as follows:1. The fracture morphology of ITO green compact display particle shape in the lesser forming pressure, and the ITO green compact have biggish intergranular space and low density; with the increasing of pressure, the intergranular space diminished and the density swelled; the unabridged ITO green compact with the high density higher than51.9%were obtained under the forming pressing of55MPa;2. Prolonging the holding time can promote the discharge of the gas and rearrangement of particle, which improve the density of ITO green compact effectively, the density is almost invariant when the holding pressure was more than4min; The ultrasonic vibration can reduce the friction between particles and die wall, and it’s effectively improve the density and well-distributed of ITO green compact, the maximum density was obtained when power of the ultrasonic vibration is1.5KW, comparing with the conventional pressing, the density was increased by0.1g/cm3, and the density difference reduced by0.07g/cm.(3) In the temperature range from room temperature to250℃, the degreasing behavior was mainly discharging of water and softening of the PVA, and the corresponding mass loss was0.736%; The PVA decompose poignant in the temperature range from250℃to400℃, and the corresponding mass loss was0.952%; The curve of TG and DSC were unchanged basically when the temperature was greater than500℃, it shows that the decomposition of the PVA completed basically. The density of ITO biscuit was increasable after CIP, the ITO biscuit with the high density higher than62.7%were obtained under the CIP of250MPa.(4) The influence of atmosphere sintering processing parameters on the performance of the ITO target are as follows:The density of ITO target was improved effectively by rapid warming; The density of the ITO target increases with increasing sintering temperatre, and the maximum density was obtained in the temperature of1550℃, the density was reduced with the sintering temperature increasing continual; Prolonging the holding time was beneficial to the densification process, when the sintering time over8h,the density was almost invariant; The decomposition of indium tin oxide was inhibited under the0.02MPa oxygen pressure. the optimal operation parameters of ITO target prepared by atmosphere sintering were as follows:the rate of temperature rise is500℃/h, sintering temperature is1550℃, sintering time is8h, and the pressure of oxygen is0.02MPa, the relative density and resistivity were up to99.58%and1.812×10-Ω·cm, and the phase of ITO target was single-phase.