| With the development of microwave technology, its application has been found in every relative part of science and technology. The development of microwave devices trends to high quality, high performance and miniaturization, and the microwave dielectric ceramics are playing more and more important role in microwave technology. The microwave dielectric ceramics with perovskite structure have the characteristics of high dielectric constant, low dielectric loss as well as temperature coefficient in high frequency, however the coexistence of the above parameters was difficult to explain when by the classic dielectric physics theory. So it was necessary to investigate the relationship between dielectric principles and the microstructure of ceramics in order to provide the basic theory of improving performance and the principle of design.In the present dissertation, we have conducted the investigation from the following four respects :Firstly the dielectric polarization theory in perovskite ceramics based on the perturbation theory of quantum was researched in order to explain the source of high dielectric constant; secondly the dielectric loss theory was investigated using the defect chemistry; thirdly the effective ways to reduce the non-intrinsic loss was investigated by resolving the source of defects in microwave dielectric ceramics and its affecting principles; lastly the reason of the significant improvement of microwave dielectric performance in perovskite ceramics doped by rare-earth elements was primarily investigated.The relationship between properties and structures in microware dielectric ceramics with perovskite structure was discussed in the total dissertation, as well as the principle of dielectric polarization and loss mechanism.On the base of summarizing the experiment data, it was proposed that the microware characters in perovskite-like tungsten bronze type structure BaO-Ln2O3-TiO2 series, complex perovskite CaO-Li2O-Ln2O3-TiO3 series and Pb-based perovskite Pb-Ca-Fe-Nb series were decided by the structure of BO6 octahedron connected each other through the point angle. By use of the in-electric field theory and Lorentz Model, the polarization equation of perovskite structure microware ceramics was obtained, and the approximate equation to explain polarization can be got by proper simplifying, with which the polarization of intrinsic perovskite structure microware ceramics can be explained at a certain degree. However, the ion structure of microware dielectric ceramics was so complicated that the result of the simplified calculation would be confirmed further by experiment.The electronic and ionic polarizing process were researched by the perturbation theory of quantum mechanics. In microwave field, when B-O ion polarized in BO6 octahedral, the field can be taken as the electron movement of B ion acting with O ion, if the interaction between B ion and O ion vibration was treated as a perturbation quantity and the impact of this perturbation quantity on the degenerate energy was evaluated. According to Jahn-Teller effect, the B-O chain in octahedral would be changed: the electron cloud of O ion would firstly be distorted and the polarization of octahedral increased, if the amount of the decreasing energy was greater than the amount of degenerate energy increase caused by the replacement of O ion, and the O ion replacement distortion would result in higher polarization of Octahedral.The dielectric loss in ceramics was investigated by defect chemistry. Through analyzing the defect model of microwave ceramics in intrinsic, donor and acceptor doping situation, the relationship between conductivity and structure in ceramics was investigated in order to study the regularity of conductive loss. The relationship of the source of defect,regularity and the loss was investigated from the grain defect, crystal edge and miscellaneous aspects. The research of point defect controlling, grain growth model controlling and process controlling were initially studied in this work.Base on the micr...
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