A method for preparing a dispersion of tin-containing metal oxide nano-particles, wherein the tin-containing metal oxide comprises tin element and an aid metallic element other than tin selected from antimony, indium, titanium, copper, zinc, zirconium, cerium, yttrium, lanthanum, niobium or a mixture thereof;
- and the tin-containing metal oxide nano-particles have an initial average particle diameter of 2-50 nm, a particle diameter distribution as defined with an Index of dispersion degree of less than 7 and a steepness ratio of less than 3, the method comprises steps of:
- (1) reacting a solution containing tin ions and a solution containing ions of the aid metallic element other tin with a solution of precipitating agent at a temperature of less than 100° C. under a non-acidic condition in an aqueous medium comprising at least one of alcohols, amides, ketones, epoxides and mixtures thereof to form tin-containing metal oxide precursor particles and a first by-product in ionic form;
- wherein the precipitating agent is selected from alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal bicarbonates, ammonia, organic bases and mixtures thereof;
- (2) separating the tin-containing metal oxide precursor particles from the first by-product in ionic form to obtain tin-containing metal oxide precursor particles substantially free of ionic impurities;
- (3) reacting the tin-containing metal oxide precursor particles substantially free of Ionic impurities with an oxidizing agent or a reducing agent at a temperature of 150-400° C. and a pressure of 5 to 10 atmospheres to obtain tin-containing metal oxide particles and a second by-product in ionic form;
- (4) coating the tin-containing metal oxide particles with a surfactant in an amount of 0.01% to 30% relative to the weight of tin-containing metal oxide particle to obtain coated tin-containing metal oxide particles, wherein the surfactant is selected from a non-silane surface modifying agent, a silane coupling agent, a titanate coupling agent, or a mixture thereof, and the non-silane surface modifying agent is selected from cationic surfactants, non-ionic surfactants, polymeric surfactants and mixtures thereof;
- (5) separating the coated tin-containing metal oxide particles from the second by-product in ionic form to obtain tin-containing metal oxide nano-particles substantially free of ionic impurities;
- (6) adding a dispersion medium and a dispersing agent to the tin-containing metal oxide nano-particles substantially free of Ionic impurities to obtain the dispersion of tin-containing metal oxide nano-particles,
- wherein, when the dispersion medium is water in step (6), the dispersing agent is one or more selected from ethanolamine, triethanolamine, triethylamine, diisopropanol amine, tetramethylammonium hydroxide, polyvinyl alcohol, methacryloxy silane, polyacrylic acid ammonium salt dispersing agent, polyacrylic acid sodium salt dispersing agent, polysiloxane dispersing agent, polyamide dispersing agent, polymer block copolymer dispersing agent;
- and when the disperse medium is an organic solvent the dispersing agent is one or more selected from octylamine, polycarboxylic salt dispersing agents, polycarboxylic-sulfonic copolymer dispersing agents, polymaleicanhydride copolymer dispersing agents, silane coupling agents, titanate coupling agents.