Preparation And Co-precipitation Process Of IGZO Powder

IGZO is a representative material for transparent metal oxide semiconductor,which belong to N-type semiconductor with a forbidden band width of about 3.5e V.It is widely used in Active Matrix/Organic Light Emitting Diode（AMOLED）,Liquid Crystal Display（LCD）,flexible display,and electronic paper fields,due to the advantages of high electron mobility,excellent optical and electrical properties.IGZO powder is used as the raw material powder of IGZO target for flat panel display,Which has high performance requirements.It is an important process for preparing high-performance IGZO targets to an obtain high-quality raw material powder.Through the preparation and research of IGZO powder,it provides guidance for the performance improvement of IGZO targets,and lays a foundation for the preparation of high-quality IGZO targets.The main research contents and conclusions are as follows:（1）The influence of the dissolution mode of the precursor was investigated during the formation of precipitation and the concentration of nitric acid on the microscopic properties of the powder when IGZO powder was prepared by co-precipitation method.The results showed that the change of the dissolution mode had an effect on the crystallinity and morphology of the precursor.When miscibled,the crystallinity of the precursor was tronger,and the morphology was an agglomerate formed by irregular particles and nearly spherical particles.the crystallinity of fractionation was the weakest,and the morphology was similar to the miscibility.the precursor crystallizes after fractional precipitation.The properties lied between the two,and the morphology was mainly irregular particles.After calcination,it was found that the phase of the powder was not affected by the change of the dissolution mode,and the grain morphology was similar after calcination,but the grain size was different,and the average grain size was the smallest（46.02 nm）when miscible.The phases of powders with different nitric acid concentrations were similar after calcination,but by changing the nitric acid concentration,it was found that different nitric acid concentrations can affect the particle size of the precursor.When the concentration of 55%nitric acid was used,the uniformity of the precursor particles was better,the average grain size of the powder obtained was the smallest.（2）The effect of pH value on the microscopic properties of the precursor and calcined powder was investigated during the co-precipitation process.It was found that when the pH value was different,the precursors were similar,but the crystallinity and morphology were different.When the pH was 7.8,it can be seen that some flake-like precipitates were linked to each other as the matrix,and there were many fine granular grains on the surface to form agglomerates;when the pH was 8.3-9.3,the morphology was normal stacking of fine grains Secondary particles are formed.After calcination,the phase change of IGZO powder is relatively large.When the pH value was 7.8-8.3,it was a mixed phase of In₂O₃ and In Ga Zn O₄;when the pH value was 8.8,it was a mixed phase of In₂O₃ and Zn Ga₂O₄;when the pH value increaseds to When the pH value increases to 9.3,the phase was Ga In O₃.According to the change of pH,the particle size increased at first and then decreased.The average grain size increased from 40.87 nm to 59.75 nm,and then decreased to 55.81 nm.The morphology was mainly irregular particles.（3）We investigated the effects of metal ion concentration during precipitation on the microscopic properties of precursors and calcined powders.The results showed that with the increase of ion concentration,the phase of the precursor did not change,but the diffraction peak intensity gradually increased,the peak shape became sharp,and the crystallinity improved.The morphologies of the precursors with different ion concentrations are were both cube and irregular block.After calcination,it was found that with the decrease of ion concentration,In Ga Zn O₄ form gradually closed to a single phase,and at the same time,the grain size also gradually increased with the increase of ion concentration.（4）The effects of different precipitants on the microscopic properties of the precursor and calcined powder were explored during the precipitation process.The results showed that the peak intensity of the precursor was relatively strong,and the crystallinity was high after the precipitation of ammonia water.At the same time,the secondary particles formed were smaller than those formed by the precipitation of sodium hydroxide.After calcination with different precipitants,the phase and morphology were different.When sodium hydroxide was used as a precipitant,the IGZO powder was a single-phase In Ga Zn O₄;when ammonia water was used as a precipitant,it was a mixed phase of In₂O₃ and Zn Ga₂O₄.After precipitation and calcination with ammonia water,the powder showed a nearly spherical shape.After precipitation with sodium hydroxide,we observed coexisting nanoparticles with irregular shapes and flake shapes.（5）The effects of calcination temperature and holding time on powder properties were investigated during calcination.It was found that with the increase of calcination temperature,the phase of IGZO powder was not affected,it was a mixed phase of In₂O₃ and Zn Ga₂O₄,but the crystal form of In₂O₃ changed.When the temperature was 800-900°C,It was a hexagonal In₂O₃ phase,and when the temperature increased to 1000-1100°C,it transformed into a cubic phase.At the same time,it was also found that the grain size did not increase with the prolongation of the holding time.Through the kinetic analysis of IGZO powder,It was found that with the increase of temperature,its kinetic index increased continuously.When the temperature was 800°C,the kinetic index was 4.28,the grain growth was slow,and surface diffusion was the dominant grain growth mechanism.When the temperature rised to 900°C,the kinetic growth index n was about 5,which was dominated by volume diffusion.At this time,the grain growth rate was accelerated.When the temperature rised to 1000-1100°C,the kinetic growth index n of the grains was about 5.5.At this time,the grains grow under the combined action of volume diffusion and grain boundary diffusion,and the grain growth rate was further accelerated.