| Composite multiferroic which operate by coupling the magnetic and electric properties between two materials, shows magnetoelectric effect by coupling of magnetoconstriction and piezoelectricity. In this materials,external electric field can lead to magnetization, vice versa, polarization can be induced by magnetic field. Because of the potential of application, the research of multiferroic become one of the important area in condensed matter physics.The main contents of this paper are as the following:(1) CoFe2O4–BaTiO3 multiferroic core-shell-type nanostructures were synthesized by a two-step wet chemical procedure,combining co-precipitation and sol–gel techniques. The nature of bonding of oleic acid with CoFe2O4 nanoparticles is determined by Fourier transform infrared spectroscopy ,and the ferrofluid was Prepared by the dispersation of the surface-modified ferrite into the surface-modified ferrite,which can disperse into the Stearic Acid imedia easily. X-ray diffraction confirmed the presence of both the CoFe2O4 of spinel and the BaTiO3 of perovskite phases, and no secondary phases were detected by this technique.(2) A few series of CoFe2O4–BaTiO3 ceramics was prepared from powders by changing the preparation conditions, which include constituent,sintering temperature,sintering duration and pressure of pressing the composite powders.The most appropriate preparation conditions, which was the mole ratio of CoFe2O4/BaTiO3 being (1:4),the pressure of 20MPa and sintering at 1150℃for 4 h, was obtained by the measurement of ferroelectric, dielectric and ferromagnetic properties.(3)Comparation of the three preparation methods : In situ, acetic acid sol-gel process (AAG) and Stearic Acid sol-gel process (SAG), by the measurement of ferroelectric, dielectric and ferromagnetic property show that The SAG can improve the ferroelectric, dielectric property,but it prejudice the ferromagnetic property. In a word the SAG was suitable mothed in the preparation of multiferroic ceramics. |
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