Regulating Effect Of Bi On The Ferroelectricity Of Ba(Ti_0.9Sn_0.1)O₃ Ceramics

Relaxor ferroelectrics based on BaTiO3 are important medium of multilayer ceramics capacitor because of their large permittivity, low sintered temperature and phase transition temperature, relaxed phase transition behavior. Conventional solid reaction method was used to prepare Ba1-3xBi2x(Ti0.9Sn0.1)O3(x=0, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%) ceramics. Then analysis and testing was done to these ceramics though XRD, Raman spectra and LCR meter. The thesis mainly investigated the phase transition and microstructure of the ferroelectrics, and explained the mechanism of the properties.After Bi-doping, the phase transition temperatures of all ceramics shifted to low temperature and the permittivity increased. With the increase of doping, the phase transition temperature became lower, but the permittivity decreased. This may be induced by oxygen vacancies.When light doping, the samples were normal ferroelectrics because there were no frequency dispersion and diffused phase transition. But the samples became relaxor ferroelectrics when x>0.4%. And with the increase of Bi-doping, the phase transition became more relaxed. This could be attributed to polar nanoregions which brought by the electric field of Bi3+—VBa″dipoles, the different radius and polarization of Bi3+and Ba2+ in the material.The loss tanδdecreased in 295～298K after Bi-doping,and the reason may be vacancies forming by Bi volatilization restrained the movement of defect in material.The Raman spectra of these samples had obvious change, some phase transitions could be inferred from the spectra. The peaks centered at about 301 cm-1 and 721 cm-1 wave number marked the relaxed extent of the ferroelectric ceramics. Though comparision, we could find that the change of Raman spectra corresponded to the variation of the dielectric properties.