| Indium Tin Oxide(ITO)is a semiconductor material obtained by doping Indium Oxide with Tin.The film of ITO should have electrical conductivity and high visible light transmittance,which is widely used in optoelectronic devices.ITO material has two crystal types:c-ITO and h-ITO.In this paper,cubic phase ITO hollow microspheres were prepared by hydrothermal method using PEG-4000 and aspartic acid(DLAA)as template.The effects of precipitant type,amount of PEG-4000 and amount of aspartic acid on the morphology of the powders were studied,and the effects of hydrothermal reaction time on the morphology and photoelectric properties of the prepared powders were also studied.The formation mechanism of ball-like hollow search is also studied.Hexagonal phase ITO microspheres were prepared by binary solvothermal method using sodium citrate as complexing agent.The effects of the volume ratio of water to ethanol,reaction time and reaction temperature on the properties of ITO powder were studied,and the formation mechanism of h-ITO micro spheres was also studied.The results showed that:Using PEG-4000 and aspartic acid as template,cubic phase ITO hollow microspheres were prepared by hydrothermal method.When the molar ratio of PEG-4000 to In3+was 5:1 and the molar ratio of aspartic acid to In3+ was 3:1,the precursor product was obtained by hydrothermal reaction at 120? for 10 h,and then the precursor was calcined at 450? for 3 h to obtain cubic phase hollow microspheres ITO powder.The outer diameter of the hollow microspheres was about 2.2?m,the inner diameter was about 2?m,and the specific surface area was 64.107 m2·g-1,the lowest resistivity is 164.03 ?·cm,the optical band gap value is 3.50 eV.Formation mechanism of c-ITO hollow microspheres:PEG-4000 forms spheroidal micelles in aqueous solution when its concentration reaches a certain value.The C-C end of DLAA will be adsorbed to the C-C end of PEG-4000 due to hydrophobicity.The outer layer of micelle is attached with a layer of DLAA molecule.The carboxyl functional group of DLAA is negatively charged,which attracts In3+and Sn4+ ions in the solution.With the decomposition of urea,In3+and Sn4+are precipitated,and the newly generated nano-hydroxide particles are deposited along the PEG-4000 spherical micelles with carboxyl functional groups.After calcination,a hollow spherical ITO material is finally formedITO powder was prepared by binary mixed solvothermal method with sodium citrate as complexing agent,and the formation mechanism of h-ITO microspheres was studied.When the water-ethanol binary mixed solvent is used as the reaction medium and the volume ratio is 1:1,the precursor product inOOH is obtained by reacting at 200? for 12 h.The precursor product was calcined in a muffle furnace at 550?for 3h to prepare a single hexagonal ITO powder,which is formed by nanometer short clavite reunion ITO micro spherical particles,the resistivity of 1.297 ?·cm.Formation mechanism of h-ITO microspheres:When sodium citrate is mixed with water-ethanol solvent,the solubility of sodium citrate in ethanol is poor.During the hydrothermal reaction,as the temperature rises,urea decomposes and OH-diffuses into the droplets.With the increase of pH,sodium citrate releases complex In3+?Sn4+cation,and OH-reacts with In3+?Sn4+cation to precipitate,resulting in the agglomeration of nano-sized short-rod-like ITO powder to form a micron-spherical structure. |
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