Study On Preparation Of Nano-ZnO And Its Microwave Dielectric Properties

ZnO is a new generational multifunctional II -VI compound semiconductor with a wide and direct band gap. ZnO nanostructures show great promising applications in opto-electric devices, surface acoustic wave devices, piezoelectricity material, field emitters, sensors, ultraviolet Lasers, solar cells and so on. Compared with other electric conduction powders, Al-doped ZnO not only has the fine electric conduction function and optical quality, but also has abundant and cheap raw materials. With the development of science and technology, Al-doped ZnO will find broader applications.In the dissertation, nanometer ZnO and ZAO powders were synthesized by homogeneous method from Zn(NO₃)₂, Al(NO₃)₃ and carbamide, respectively. The influence of reaction temperature, mixture ratio of raw materials and heat-treatment temperature on particle shape, size and the dielectric property of ZnO powders was investigated. The influence of Al-doped concentration, heat-treatment temperature and heat-treatment time on dielectric properties of ZAO powders were also investigated at the same time. The results show that the size of ZnO powders decreased with the increasing of temperature, mol ratio of carbamide and Zn²⁺ and degree of supersaturation. The reactants concentration has no effect on the grain size, but the dispersion conditions of powders were improved. The ZnO particles become smaller and homogeneous after 600℃ heat-treatment. Both the real and imaginary parts of complex permittivity of the powders decrease with the decreasing of reaction temperature. They increase with the decreasing of mixture ratio of Zn(NO₃)₂ and carbamide. The increasing of powder's lattice defect leads to increase them. The size of ZAO powders decreases with increasing of Al-doped concentration, and the particles shape is torispherical. The size of ZAO powders increases with increasing of heat-treatment temperature and heat-treatment time. The real part and imaginary part of permittivity of mixture of the ZAO powders and paraffin increase with increasing of Al-doped concentration. However, the Al-doped heavily is not appropriate due to the formation of ZnAl₂O₄. The real part and imaginary part of permittivity of mixture of the ZAO powders and paraffin increase with increasing of heat-treatment temperature and heat-treatment time.