The Preparation And Properties Of The Ba_0.8Sr_0.2TiO₃/CoFe₂O₄Multiferroic Layered Magnetoelectric Materials

Multiferroic magnetoelectric materials have the ferroelectric and ferromagnetic but some time they have the magnetoelectric coupling effect at the same time. Magnetoelectric coupling effect is defined as a dieletric polarization induced by an external magnetic field, or a magnetization induced by an external electric filed.The characteristics of the magnetic field and electric field transformation makes the multiferroic magnetoelectric materials in information storage, the magnetic field sensor, filter and phase shifter has great potential for application. Single-phase magnetoelectric multiferroic magnetoelectric materials due to the coupling effect is weak, the multiferroic magnetoelectric composite materials has become the research hot spot. This paper adopts the sol-gel method Ba0.8Sr0.2TiO3/CoFe2O4layered magnetoelectric composite membrane, sol-gel preparation and step by step sintering Ba0.8Sr0.2TiO3/CoFe2O4layered magnetoelectric composite ceramic, the main research results as follows:(1) Research the layered multiferroic magnetoelectric composite dielectric tunability using elastic theory combined with the thermodynamics method. Established the CoFe2O4Ba0.8Sr0.2TiO3/CoFe2O4three layer structure model, researched on the material of the feasibility of the control performance by changing the film thickness ratio and the external magnetic field. Magnetostriction stress through the interface control Ba0.8Sr0.2TiO3layer stress, so as to realize by adjusting the magnetic field to adjust the dielectric properties of ferroelectric layer, in combination with Timeshenko elastic theory, the introduction of CoFe2O4magnetostrictive effect, and gold Pittsburgh landau theory is used to calculate the Ba0.8Sr0.2TiO3the dielectric properties of each layer thickness and the relationship between the applied electric field and temperature field.(2) The sol-gel method of spin coating process is studied in the preparation of Bao.8Sro.2Ti03relevant methods of ferroelectric thin film and CoFe2O4ferromagnetic film, studied the Ba0.8Sr0.2TiO3configuration of the precursor solution and glue film, wet film preparation links such as heat treatment process, mainly studied the preparation of Ba0.8Sr0.2TiO3thin film when the choice of solvent, studied the amount of citric acid and ethylene glycol adding to the rightness CoFe204crystal structure and the influence of gram size.(3) Study the Ba0.8Sr0.2Ti03/CoFe2O4layered composite membrane electrical and magnetic properties. CoFe2O4spin coating as the increase of the number of the ferroelectric composite film is increased, the leakage current is slightly lower, the thickness of different CoFe2O4layered composite film dielectric constant decreases with the increase of frequency, dielectric loss first appeared with the increase of test frequency peak phenomenon, along with the increase of thickness of CoFe2O4, dielectric loss increases, and moving in the direction of high frequency dielectric loss peak. Saturation magnetization and remanent magnetization is along with the change of CoFe2O4spin coating for approximate linear, but as the change of CoFe2O4thickness showed certain nonlinear, the coercive force He composite film of coercive field CoFe2O4spin coating as the increasing of the number of first increases then decreases, composite materials are magnetic anisotropy.(4) Research the magnetoelectric coupling effect of the Ba0.8Sr0.2TiO3CoFe2O4layered composite thin films. The polarization and coercive field of the Ba0.8Sr0.2Ti03/CoFe2O4layered composite thin films decrease after a constant magnetic field, the thickness of different CoFe2O4layered composite membrane in the test range respectively in a magnetic field is magnetoelectric effect coupling coefficient peak. Different electrode was studied in Ba0.8Sr0.2TiO3/CoFe2O4layered composite membrane structure and electrical properties and the effect of growth on the BaPbO3bottom electrode Ba0.8Sro0.2TiO3thin film easier to preferred orientation, Ba0.8Sr0.2TiO3/CoFe2O4layered composite membrane have more saturated electrode polarization, the smaller the residual polarization and coercive field, using BaPbO3/Pt electrode structure, layered composite film shows a better performance of iron, oxide electrode BaPbO3can largely improve Bao.8Sro.2Ti03/CoFe204fatigue properties of layered composite membrane.(5) Prepared Ba0.8Sr0.2TiO3/CoFe204layered composite block respectively by sol-gel chemical reactions and solid reactions with step by step sintering and adhesive, compares the electrical properties of layered magnetoelectric piece of material, magnetic properties and magnetoelectric coupling performance of the layered composite block prepared with the two methods. Microwave combustion sol-gel particles small Ba0.8Sr0.2TiO3and CoFe2O4powders, sintering way step by step effectively overcome the differences of two material shrinkage caused by the ceramic crack. Solid instead should be the method of layered composite ceramic ferroelectricity significantly lower than the sol-gel method of layered composite ceramic ferroelectricity, sol-gel method of layered magnetoelectric ceramic leakage current and dielectric constant is small, the solid should be prepared on the magnetic anisotropy of layered magnetoelectric ceramic more apparent, sol-gel method of layered magnetoelectric ceramic ferroelectric and ferromagnetic layers between the depth of a certain permeable zones, is slightly bigger than the magnetoelectric coupling coefficient solid instead should be prepared sample, two methods of layered magnetoelectric ceramic inverse magnetoelectric coupling coefficients decrease with the increase of frequency and phase difference has shown obvious regularity.