Mechanochemical Synthesis of Indium-Tin Oxide Powder

Abstract

Submicron indium oxide powder was obtained by the oxidation of metal and urea-hydrogen peroxide adduct (UHPA) mixture reactively milled with hydrogen peroxide in high energy mill according to the reaction: 2In + 3 (NH 2 ) 2 CO-H 2 O 2 → In 2 O 3 + 3H 2 O + (NH 2 ) 2 CO Reactive milling (RM) of In with UHPA and hydrogen peroxide resulted in the formation of RM precursor - a complex mixture of submicron metal particles, traces amount of In 2 O 3 dispersed in an organic matrix. High resolution transmission and scanning electron microscope were used to study the microstructure of the precursor. Study of a dynamic change of IR spectra of In-UHPA in H 2 O 2 allowed us to suggest formation of In-urea complex. Reactive milling of UHPA with In and H 2 O 2 resulted in gradual disappearance of 0-0 stretching band and formation of a new bond in the 500-600 cm -1 range, presumably due to In-O, while carbamide bands did not change. Thermal treatment of this RM precursor at 473K for 3-4 hours resulted in complete disappearance or evaporation of organic compounds. Further heating up to 573-673K in air/oxygen led to the oxidation with the formation of indium oxide, having typical IR spectra identical to one synthesized by wet chemistry and annealed at 673K.. Our study showed that reactive milling with combination of thermal treatment can be used to syntheses submicron powders of a indium, tin oxides and indium-tin oxides (ITO). Sintering process of ITO powder obtained by RM was also studied.