Preparation and electrical conductivity of TiO₂@Sb_xSn_1-xO₂ core-shell composite particles by homogeneous precipitation

Core shell conductive composite powders of TiO₂ coated with Sb_xS_n1-xO₂ antimony-doped tin oxide(ATO) nanoparticles were prepared with urea as the precipitant by homogeneous precipitation. The as-prepared composite powders were characterized by SEM, EDS, HRTEM, XRD, XPS, electron paramagnetic resonance(EPR), FTIR and laser particle size analyzer(LPSA), respectively. Effects of several main experimental parameters on the resistivity of the TiO₂@ATO powders were primarily investigated. A possible mechanism for coating of ATO nanoparticles on the surface of TiO₂ microspheres was proposed. The results show that when the molar ratio of metal cation to urea for precipitation reaction is 1:10 at the temperature of 92℃, the release amount and rate of OH^- are moderate. At the same time, SO₄^2- was introduced as a catalyst to reduce the nucleation barrier of metal cations, in which the optimum molar ratio of SO₄^2- to Cl^- is 1:25. Uniform, continuous and compact shell layer of ATO of the obtained product is formed on the surface of the TiO₂ with a thickness of approximately 15 nm. When completely covered, the resistivity of composite powders decreases first and then, when the molar ratio of Sn to Sb reaches 12:1, changes little with the increase of Sb doping amount. Under the optimum experimental conditions, TiO₂@ATO has good electrical conductivity with the resistivity of 7.5 Ωcm.