均匀沉淀法制备核-壳型TiO2@SbxSn1-xO2及其导电性能

以尿素为沉淀剂，采用均匀沉淀法包覆改性TiO₂，制备了核壳型TiO₂@Sb_xSn_1-xO₂（ATO）复合导电粉体，利用SEM、EDS、HRTEM、XRD、XPS、顺磁波谱仪（EPR）、FTIR及激光粒度仪（LPSA）等对其进行表征，并对其导电性的主要影响条件进行了研究及分析，提出了均匀沉淀包覆及反应机制。研究表明，反应温度为92℃时，尿素与金属阳离子摩尔比为10∶1的情况下，OH-释放量及释放速率适中，引入SO₄2-作为催化剂，降低金属阳离子成核能垒，且SO₄2-与Cl-最佳摩尔比为1∶25时，所得产品的纳米Sb_xSn_1-xO₂（ATO）壳层在TiO₂表面包覆均匀连续完整，其厚度约为15 nm。当包覆完全时，随着Sb掺杂量增加，复合粉体电阻率降低，Sn与Sb摩尔比达到12∶1时，再增加Sb含量，其电阻率不变。最优制备条件下，复合粉体电阻率值为7.5 Ωcm，导电性能良好。 

Preparation and electrical conductivity of TiO2@SbxSn1-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, SO₄2- was introduced as a catalyst to reduce the nucleation barrier of metal cations, in which the optimum molar ratio of SO₄2- 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.