Preparation And Electrical Properties Of Cubic And Spherical ITO Powders

Tin-doped indium oxides(ITO)film has been widely used in display,photovoltaic and lighting fields due to its high transmittance and excellent electrical properties.As the basis of ITO industry chain,inherent photoelectric properties of ITO powder should go hand in hand with the performance of ITO films.In this study,without heat treatment,low-resistivity ITO nanocubes were successfully prepared with change in alkali source and solvothermal conditions in one step by the solvothermal method.In addition,monodisperse ITO sub-microspheres were synthesized using L-histidine(L-His)as a shape control agent and triethylamine(TEA)as base.And the phase transformation mechanism and the growth mechanism of cubic ITO nanoparticles have been intensively explained.The effect of different reaction conditions on the phase composition,microstructure and electrical properties of ITO powder was discussed.On the one hand,when NaOH was used as inorganic base with tetramethyl ammonium chloride(TMAC)assisted,cubic ITO nanopowders were prepared with high dispersibility and high conductivity.The phase composition,size and morphology of ITO nanopowders were controlled by changing solvents,reaction temperature and reaction time.The effect of NaOH concentration on the electrical properties of ITO nanopowders was also investigated.Cubic ITO nanopaticles with uniform size and good dispersibility were prepared at 250? for 24 h with ethylene acohol as solvent.And the average particle size was 46 nm,and the smallest specific surface area was 22.82 m2/g.As reaction time was prolonged,the rod-like indium hydroxides were transformed to cubic In2O3 nanoparticles gradually through the dissolution-recrystallisation mechanism.When the reaction time was 3 h,the phase transition process finished.During the formation of In2O3 nanocrystals,the growth rate perpendicular to(200)plane reduced,caused by the adsorption of glycol and tetramethyl ammonium ion on the surface of particles,which induced the formation of cubic-shaped ITO nanoparticles.With the increase of NaOH concentration,the particle size became larger,the crystallinity increased,the carrier concentration increased,the electron mobility decreased,and the decrease of the mobility is less than the increase of the carrier,which eventually led to the decrease of the resistivity of ITO namopowders.When the NaOH concentration was 2 M,the lowest resistivity of ITO powder was 0.2 ?·cm.On the other hand,TEA,triethanolamine(TEOA)and ethanolamine(ETA)were used as the base sources,and no structural guidance agent was added to prepare good dispersible ITO nancubes.Using TEA as base,ITO nanocubes with an average particle size of 17 nm were prepared in EG for 96 h,which has the lowest resistivity of 0.7 ?·cm.When TEOA was used as a base,cubic ITO nanopowder with particle size of 20 nm was obtained in dimethylformamide(DMF),which has the lowest resistivity of 0.3 ?·cm.The required reaction time was reduced to 12 h.When ETA was used as base and the reaction time was 12 h,the powders synthesized in polyols and DMF were irregular shapes,and the resistivity ranged from 1.5 to 2.4 2-cm.When TEA was used as an alkali source,without adding L-His,the mixture of spherical and cubic particles were obtained at 250? for 24 h or even 96 h.In order to prepare monodisperse ITO submicron spheres,shape control agent L-His was add.When the TEA concentration was 1 M and the L-His concentration was 0.05 M,ITO submicron spheres were obtained at 250? for 24 h.The average particle size was 0.29 ?m,and the resistivity was 0.7 ?·cm.The addition of L-His decreases the resistivity of ITO powders by an order of magnitude.Meanwhile,the resistivity of ITO powders decreased with the increase of L-His concentration.When the concentration of L-His was 0.2 M,the lowest resistivity was 0.2 cm.