The Investigation Of Synthesis And Electromagnetic Characters Of Barium Titanate And Its Modified Ceramic Materials

In this dissertation, the ceramic powder of barium titanate (BaTiO₃, BT) and its modified compound material of carbon black and barium titanate (CB/BT) were synthesized by sol-gol method, respectively. The electromagnetic (EM) wave absorbing properties of the BT and CB/BT respectively filled up the epoxide resin (EP) were investigated for the first time.The mircrostructure and morphology of powders were characterized by infra-red spectrum (IR), X-ray diffraction (XRD), Raman Spectrum, ultraviolet spectrometer (UV), scanning electronic microscope (SEM), different scanning calorimeter (DSC) and thermogravimetry-differential thermal analysis (TG) in different temperature. TEM. At several temperature elevation stages, the sample was submitted to IR analyzing for the elucidation of decomposition process. Thermal stability of the BaTiO₃ xerogel powders were investigated in nitrogen by DSC-TG. The crystallization and phase transformation of BaTiO₃ xerogel powders, from which amorphous to perovskite were studied by X-ray diffraction. The volume electrical resistivity of the BaTiO₃ powders at different treatment temperature was investigated. It was shown that the xerogel powders obtained were amorphous. Upon heating, the amorphous powders crystallized continuously, and grain size was increased with the treatment temperature power-up. The treatment temperature has important effect on the thermal decomposition process, crystallization and phase transformation, volume resistivity of the BaTiO₃ powders, and the thermal decomposition reaction proceeded in three stages: solvents removing, organic ligands decomposing, and amorphous solid BaTiO₃ forming.Using a coaxial waveguid technique, the complex relative permittivity and permeability of the BT wer measured in the frequency range of 2¹8GHz. The EM absorption of BT/EP composite flat slab with 5, 10, 15, 20, 25 and 30 wt. % mass fractions and thicknesses of 1, 2, 4 and 6mm were tested by reflection/transmission technique in the X and Kubands, respectively. It was indicated that the real part ε' of permittivity for BT decreases from 32 to 5, and the imaginary part ε" of permittivity decreases slowly from 25 to 5, and both the real part and the imaginary part of permittivity for BT show significant variation with the frequency and the magnitude of both parts decrease with increasing frequency. The real part μ' of permeability for BT was approach 1.0, whereas the imaginary part μ'' of it is almost zero and nearly remains constant during the frequency region studied. Those results demonstrate that the BT hardly has diamagnetism and magnetic loss, The EM absorption...