Preparation And Dielectric Properties Research Of Bismuth Ferrite And Nano Barium Titanate

Ferroelectric materials is a class of ferroelectric effect materials. Due to its unique ferroelectric properties,high dielectric constant, electro-optic, acousto-optical and nonlinear optical effect, it has great value application in field emission devices, ceramic capacitors, light switch, sound and light converters, optical information storage devices and optical frequency doubling devices.In this paper, on the one hand, bismuth ferrite ceramics which were doped with different proportions of Sm were prepared by a rapid liquid phase sintering method. On the other hand, nanocrystalline barium titanate ceramics were prepared by oxalate precipitation method and plasma sintering process. Finally, ferroelectric and dielectric properties of ferroelectric System nanocrystalline ceramics were systematic studyed, and the specific contents are as follows:(1) In this paper, Sm-doped bismuth ferrite ceramics with different Sm content of 0.13,0.15, 0.17 were synthesised by conventional solid phase sintering. The material microstructure were characterized by scanning electron microscopy (SEM),and the results showed that Sm-doped samples exhibited higher density and smaller grain sizes.(2) Ferroelectric properties of Sm-doped bismuth ferrite ceramic were systematic studyed, and the results showed that the leakage current of Sm doped bismuth ferrite ceramic decreased significantly, the ferroelectric shifted more obvious. Moreover, by comparing the ferroelectric properties, Sm-doped iron bismuth ceramic can increase the polarization of bismuth ferrite ceramic, which the Sm-doping content of 0.13 showed the best performance.(3) The dielectric properties of different grain size of barium titanate ceramics were systematic analyzed by broadband dielectric impedance. The size of barium titanate nanocrystals experience from 20nm to 1000nm. By a dielectric at different temperature phase transition of nanocrystalline ceramics, the results showed that permittivity was strongly dependent on temperature characteristics. With the grain size reduced,phase transitions become more diffuse. Different nanocrystalline barium titanate ceramics exhibited peculiar phase transition: barium titanate with a size of 70nm retained a integrity of the ferroelectric phase transition, while for the size of 100nm and 20nm, their ferroelectric phase transition disappeared.(4) The relaxation mechanism of barium titanate ceramics whose size is 70nm was intensively analyzed,that is giant low frequency dielectric permittivity real portion (up to 58000) phenomenon is due to the Maxwell-Wagner effect of the applied electric field which caused a large number of internal grain boundary charge accumulation cause. Its significant thermal activation effects were found by the relationship between the dielectric loss and the frequency. This thermal effect was in line with Debye relaxation model in a certain range.While for the Debye model deviation caused by the phenomenon of giant dielectric constant at low frequencies, it was caused by interfacial polarization influences.