Preparation And Investigation Of Target With High-Density Based On Indium Tin Oxide Powders

Indium tin oxide(ITO)films are studied and applied in the fields of displays,solar cells and sensors.The mainstream and advanced production method of ITO films is magnetron sputtering method,which utilizes ITO targets.Therefore,high-quality ITO target is the prerequisite for preparing films with excellent properties.China has become a major producer of ITO conductive glass in the world.However,Chinese flat panel display industry relies on imports of ITO target materials from Japan and South Korea,and there is no competitive high-density ITO target production base in China so far.Therefore,it is urgent to solve the localized production of high-density ITO target.In recent years,there are few literatures and basic theory research about preparing ITO target in China.Moreover,the reported preparation process from foreign literatures and patents is brief,and ITO target production technology is strictly confidential to China.The core problems of ITO target preparation technology are the improvement of target density and reduction of target resistivity.In this work,118,64 and 44 nm ITO powders are prepared by coprecipitation method.285 nm ITO powders are designed and prepared by one-step solvothermal method.Four powders are used as raw materials.ITO targets are prepared by normal pressure sintering method with different particle gradation models.Four main conclusions show as follows.1.Prilling process for powders,molding process for green bodies and sintering process for targets are optimized.Optimized prilling process:1 wt%polyvinyl pyrrolidone(PVP)and 1.5 wt%polyvinyl alcohol(PVA).Optimized molding process:Dry-pressing-Cold isostatic pressing(CIP)-DewaxingCIP-Vacuum-O2-CIP in O2.Optimized sintering process:sintering temperature of 1550? and holding time of 10 h.The stacking process of ITO particles was studied by unary-size particles regular tetrahedral stacking model.ITO targets with single cubic phase are prepared by 285,118,64 and 44 nm ITO powders.The relative densities of targets are 99.27%,99.29%,99.33%and 99.31%,respectively.The resistivities of targets are 4.11 × 10-4,4.05 ×10-4,3.97 × 10-4 and 4.17 × 10-4 ?·cm,respectively.2.In order to improve the stacking density of ITO particles,binary-size particles filling model is designed and first used to study the stacking process of ITO particles.Smaller spherical particles are filled in the spaces between larger spherical particles to increase the stacking density.Six particle gradations are designed,containing 285&118,285&64,285&44,118&44,118&64 and 64&44 nm.ITO targets with single cubic phase are prepared by six designed particle gradations.The relative densities of targets are 99.19%,99.42%,99.57%,99.30%,98.92%and 98.34%,respectively.The resistivities of targets are 3.01 × 10-4,1.83 × 10-4,0.92 × 10-4,2.45 × 10-4,3.79 × 10-4 and 4.25 × 10-4 ?·cm,respectively.In the binary-size particles filling model,the particle sizes of two kinds of spherical particles meet the formula d=((?)-1)× D.Importantly,this formula applies to 285&44 nm binary-size particles filling model.3.In order to optimize the stacking model,binary-size particles interstitial filling stacking model is designed and first used to study the stacking process of ITO particles.Smaller spherical particles are filled in the spaces between larger spherical particles to increase the stacking density.Six particle gradations are designed,containing 285&118,285&64,285&44,118&44,118&64 and 64&44 nm.ITO targets with single cubic phase are prepared by six designed particle gradations.The relative densities of targets are 99.63%,99.59%,99.22%,99.43%,98.95%and 98.45%,respectively.The resistivities of targets are 0.86 × 10-4,0.91 × 10-4,2.05 × 10-4,1.41 × 10-4,2.45× 10-4 and 3.23 × 10-4 ?·cm,respectively.In the binary-size particles regular tetrahedral interstitial filling stacking model,the particle sizes of two kinds of spherical particles meet the formula d =((?)-1)×D.Significantly,this formula applies to 285&64 nm binary-size particles model.In the binary-size particles regular octahedral interstitial filling stacking model,the particle sizes of two kinds of spherical particles meet the formula d=((?)-1)× D.Importantly,this formula applies to 285&118 nm binary-size particles model.4.In order to further optimize the stacking model,tenary-size particles gradation stacking model is designed and first used to study the stacking process of ITO particles.The model is stacked by three powders with different particle sizes.Smaller spherical particles are filled in the spaces between larger spherical particles to increase the stacking density.Four particle gradations are designed,containing 118&64&44,285&64&44,285&118&44 and 285&118&64 nm.ITO targets with single cubic phase are prepared by four designed particle gradations.The relative densities of targets are 99.29%,99.60%,99.64%and 99.67%,respectively.The resistivities of targets are 1.17× 10-4,0.86 ×10-4,0.82 2×10-4 and 0.79 × 10-4 ?·cm,respectively.In the ternary-size particles gradation stacking model,the particle sizes of three kinds of spherical particles meet the ratio relationship 1:(?)-l:(?)-1.Significantly,this ratio relationship applies to 285&118&64 nm ternary-size particles model.