Synthesis Of The ITO Nanopowder And Its Photoelectric Properties

Transparent conductive indium tin oxide（ITO）has excellent electrical conductivity,hgh visible light transmittance and chemical corrosion resistance,are widely used in all kinds of photoelectric devices.It has two kinds of structure the cubic structure（c-ITO）and the six-party corundum（h-ITO）.C-ITO shows good stability and high conductivity is mainly used in the preparation of transparent conductive film,h-ITO has a high ethanol sensitivity and high catalytic activity.Usually cubic phase is easy to get under atmospheric pressure,and the six-party corundum phase need to preparation of high temperature and high pressure conditions.This article use coprecipitation method and hydrothermal method to prepare ITO powder,the research of the system is under atmospheric pressure by changing the amount of inorganic salt dispersant in the coprecipitation achieve the change of powder crystal structure and morphology.Under the condition of not adding organic solvent,by changing the parameters of water in the thermal and reaction steps,get a different ITO powder crystal type and morphology.Results show that unlike traditional preparation h-ITO under high temperature and high pressure,the coprecipitation with urea as precipitant,adding ammonium sulfate,ammonium acetate,ammonium bicarbonate as inorganic salt dispersant,h-ITO nanopowders were obtained after 750 ℃calcination.When the molar ratios of（NH₄）₂SO₄ and In are 1:3.45 and 1:1.73,h-ITO nano powder with good crystalline were prepared;Without adding（NH4）2S04 and the molar ratio of（NH4）2S04 and In was 1:1.15 c-ITO nano powders were obtained.（NH4）2S04 added quantity plays an important role in type of crystal transformation.with the increase amount of（NH₄）₂SO₄,powders’ morphology and phase structure are changed,the morphology change from octahedral with spherical ball to spherical ball Cubic phase ITO shows a better electrical performance with low resistivity of 0.64 Ω·cm.H-ITO compared with c-ITO structure contains more oxygen vacancies,under the same excitation wavelength,hexagonal phase ITO emission light intensity is relatively higher.Using hydrothermal route,at 120 ℃ to 140 ℃ hydrothermal temperature the precursor was InOOH,after 550 ℃ calcination cubic phase ITO powders with cube shape were obtained;from 160 ℃ to 240 ℃hydrothermal temperature the precursors were mixture of both In（OH）3 and InOOH,the corresponding oxide crystal structure were c-ITO and h-ITO powders;Temperature rise to 250 ℃,the precursors were InOOH,after 550 ℃ calcination h-ITO with sphere shape were obtained.In hydrothermal condition at 140 ℃ for 12 h,the average size of the cube was 230 nm with good crystallization,its resistivity is 1.247 Ω·cm,compared with c-ln203 has high optical band gap of 3.685 eV.The oxygen vacancies content of Ols spectrum in c-ITO lattice is 17.534%,while in h-ITO is 36.373%,h-ITO compared with c-ITO structure contains more oxygen vacancies,two kinds of powder in 260 nm at room temperature under the excitation wavelength,photoluminescence of six emission peaks are located in the blue area,respectively is:411,424,450,470,483 and 450 nm,h-ITO photoluminescence intensity is higher than c-ITO when water fluid temperature is 120 ℃ and 140 ℃ when the powder morphology of cubes,particle size increased from 120 nm to 170 nm;When the water temperature is above 160 ℃ polyure get irregular shape of ITO particles,when the water temperature is above 200 ℃,the powder morphology were approximately spherical,powder particle size increases with the increase of reaction temperature.When hot water temperature of 250 ℃,the average particle size was 20 nm.By co-precipitation-hydrothermal method,at 250 ℃ water fluid temperature after 550℃ calcination,preparated c-ITO nanometer powders with good crystalline,addition of more precipitant don’t change the morphology of powders,when n（In3+）:n（CO（NH2）2）= 1:15,powder minimum resistivity is 1.077,with the increase of the amount of urea,the optical energy gap value climb up and then decline.When n（In3+）:n（CO（NH2）2）= 1:30,optical energy gap value was 3.706 eV.