| Indium tin oxide（ITO）thin films are widely used in display devices,solar cells,gas sensors,etc.due to their excellent properties,and therefore the demand for sputtering targets is increasing.It is generally accepted that ITO targets with high densities and homogeneity sputtering produce films with low resistivity.In modern industrial production,the general use of cold isostatic pressure to improve the density of raw blanks,but the effect is still not ideal,in the cold isostatic pressure of 500 MPa can only get the relative density of 58%of the blank,and need to sinter at 1600℃for up to a week to get the relative density of 99%of the ITO target,not only a long period,and huge energy consumption.Therefore,improving the density of raw blanks,reducing the sintering energy consumption,and shortening the preparation cycle are the urgent problems to be solved at this stage.This paper focuses on the main process flow of ITO target preparation,using cold sintering to prepare ITO billets,and using microwave sintering method with faster heating rate and higher sintering efficiency to replace conventional sintering to shorten the sintering cycle and reduce energy consumption,and comparing the differences of different raw material powders in cold sintering-microwave sintering.By changing the process parameters,various influencing factors in the preparation of ITO targets were investigated to obtain the optimized parameters for the preparation of ITO targets.The microscopic morphology,relative density of phase composition and resistivity of the powder,plain billets and targets were also tested using scanning electron microscope,X-Ray diffraction analyzer,four-probe,densitometer and other testing equipment.The main research contents and conclusions of the full paper are:（1）In order to improve the relative density of raw ITO billets and reduce the requirements for subsequent sintering,this paper uses hydrothermal ITO powder as raw material and prepares raw ITO billets by cold sintering molding,and investigates the effects of different cold sintering pressures,temperatures,and holding times on the density of raw billets.The results showed that the billet density increased significantly with the increase of pressure when the pressure was lower than 200 MPa,and then it did not change significantly with the increase of pressure.The relative density of the raw billet increased with the increase of temperature,and the density did not change significantly when the temperature was higher than 400℃.The density of raw billets showed a positive correlation with the cold sintering holding time below 2 h.After the holding time reached 2h,the increase of holding time had no effect on the density enhancement.The ITO billets with a relative density of 70.8%were prepared under the conditions of cold sintering temperature of 400℃,pressure of 200 MPa,and holding time of 2 h.The relative density was significantly improved compared with that of mold pressing.（2）The choice of raw material powder plays a crucial role in the preparation of high-quality ITO sputtering targets.In2O3-SnO2 mixed powder prepared by vapor phase method was used as raw material instead of hydrothermal ITO powder,and the ITO targets were prepared by cold sintering-microwave sintering.The ITO billets with a relative density of 73.4%were prepared at a cold sintering temperature of 400℃,a pressure of200 MPa,and a holding time of 2 h.ITO targets with a relative density of 99.5%and a resistivity of 3.334×10-4Ω·cm were prepared at a microwave sintering temperature of1550℃,a sintering time of 2 h,and an oxygen flow rate of 5 L/min.The relative density and electrical properties were significantly improved and the grain size was finer than those of ITO targets prepared from hydrothermal ITO powders. |
