Preparation And Performance Research Of Doped-ZnO Conductive Powder

ZnO doped systems have attracted a lot of attention all over the world due to theirgood conductivity, high whiteness, environmentally friendly behavior and non-toxicproperty.These ZnO materials are mainly used as antistatic agent and have ignificancein research and application, and their market demand is growing rapidly. Thepreparing process and conductive mechanism of ZnO conductive powder have beeninvestigated in this thesis. The Al-doped ZnO conductive powder was prepared byhomogeneous precipitation, using nitrate and urea as main starting reagent. Theconductivity was measured by multimeter. X-Ray Diffraction （XRD）, ScanningElectron Microscope （SEM） and X-ray photoelectron spectroscopy （XPS） were usedto characterize Structure and morphology of conductive powder.The effects of technological parameters, such as doping content, calciningtemperature and calcining atmosphere, etc, on conductive properties of doped ZnOpowders were analysed and the optimal technological parameters were given asfollows: under a heat treat condition of 500℃and hydrogen atmosphere, theconductivity of 1.5% Al doped ZnO powder is 1.05×10⁵Ω·cm and its average particlesize is 8.6μm; The conductivity of 1.5% Ga doped ZnO powder is 3.142×10⁴Ω·cmand its average particle size is 2.638μm.The number of conduction electrons increase according to the doping content ofAl or Ga. The substitution of doping ions for zinc ions weakens the electron bindingcapacity of ionic bond. The number of free electrons activated from valence electronsincrease, which make excess electrons show up in the bottom of conduction band, andthe carrier concentration of the internal crystal increase accordingly. Moreover,oxygen vacancies are generated in the doping process. With the increase of dopingcontent, number of free electrons and carrier density, the conductivity of powderdecreases.The effects of co-doping ratio of Al and Ga, reaction temperature, reaction time,calcining temperature on conductive properties and crystal structure of doped ZnOpowders were examined using orthogonal experiment method. Significant factorsturned out to be reaction temperature and reaction time. Al_2p and Ga_3d peaks in XPSdata show the formation of Al and Ga co-doped ZnO, and the conductivity of resulting powder is 3.3×10⁴Ω·cm. Al and Ga co-doped ZnO with low resistivity wassynthesized and its conductive property is better than that of domestic overseassimilar product.