Dielectric Properties And Impedance Study On Doped Barium Titanate

The research on pure BaTiO3 for dielectric and piezoelectric properties have been studied systematically,cause a lot of work doing in recently years.When it comes to doped barium titanate,the property of impedance and conductivity mechanism still few.Therefore,the subject eyes on the electrical properties of doped barium titanate with different systemsThe doped barium titanate ceramics were prepared by chemical precipitation and solid phase method.The effect of doping on the phase structure of the system was studied by X-ray diffraction and Raman spectroscopy.Aiming to study the electrical properties of doped ceramics,the dielectric properties,impedance performance and so on were took into consideration.The main research contents and results are as followFirstly,Al3+ doped BaTiO3 system was prepared by chemical precipitation method.The dielectric properties of the doped ceramic showed that the system had a very small frequency variation in a lower temperature range(<200?),where its frequency variation(?)is less than 0.01,that reflecting the good frequency stability of the system.The P-E curve of the ceramics was obtained by ferroelectric testing.Compared with pure barium titanate,the doped samples show the phenomenon of "waist-tied" hysteresis loop,and the polarization was decreasing from 13.5 ?C/cm2 to 7.5 ?C/cm2.Secondly,CaCu3Ti4O12(CCTO)ceramic powder was prepared by sol-gel method,and ceramic samples of BT/CCTO with different contents were prepared by solid phase method.In the process of test and analysis,it was found that the frequency dependence of the system increased with the increase of CCTO content,showing that the performance of the system at low frequency was better than that at high frequency,and the dielectric constant decreased first and then increased.Based on the analysis of electrical modulus and impedance,th corresponding equivalent circuit iFinally,the effect of different equivalent ion doping on barium titanate ceramics were studied.Ca2+ and Cu2+ ion were selected for doping respectively.For Ca2+ doped system,the dispersion factor ? is 1.49-1.79,and for Cu2+ doped system is 1.21-1.39,which indicates that both doping promote the transition from barium titanate to relaxed ferroelectrics.In addition,the conductive mechanism of different doped barium titanate ceramics was studied by impedance spectroscopy,and the activation energy of the material system was calculated.The activation energy of Ca2+ doped system decreases from 1.02 eV to 0.83 eV;for the C2+ doped system,the activation energy of grain decreases from 0.92 eV to 0.68 eV,and the grain boundary decreases from 1.02 eV to 0.42 eV.