Study On Preparation And Dielectric-ferromagnetic Properties Of BaTiO₃/CoFe₂O₄Composite

BaTiO₃/CoFe₂O₄composite is a typical dielectric/ferromagnetic composite withboth adjustable inductance and capacitance, which make it a promising material forMultilayer chip composite components. The study on preparation, microstructures,dielectric-ferromagnetic properties and interdependent relationships of the compositeis carried out.The direct solution synthesis method was used to prepare BaTiO₃nanoparticlesand CoFe₂O₄nanoparticles. The nanoparticles are high pure, ultrafine, homogeneousand high active. Mechanism analysis shows that the direct solution synthesis methodessentially combines both chemical coprecipitation method and mechanochemicaleffect, which make it a good prospect of applications on preparing ultrafine fine forhigh performance ceramic components.BaTiO₃/CoFe₂O₄composites with different fractions were prepared usingconventional sintering method. With the decrease of BaTiO₃content, the changetrend from the tetragonal structure to the cubic phase structure is observed. Thecomposite ceramic present both typical ferroelectric and ferromagnetic. Results oftemperature dependence of dielectric constant reveal that, with the increase ofCoFe₂O₄content, the Curie temperature dramatically decreased from130℃to85℃,then rises up gradually and shifts to higher temperature, while the dielectric constantdecreased constantly. With the increase of BaTiO₃content, dielectric constantincreases obviously. Except the samples with x=0and x=0.1, all the other samplespresent obvious resonant peak, and with the increase of BaTiO₃content, the resonantfrequency reduces and tends to shift toward lower frequency. For the sample withx=0.5, the real part of permittivity stabilizes at around235from106Hz to107Hz.The saturation magnetization shows strictly linear decline with the increase ofBaTiO₃content. With the increase of BaTiO₃content, the initial permeabilitydecrease. With the frequency change from107Hz to5×108Hz, the initialpermeability of about1.5remains unchanged. Hydrothermal solution method and direct solution method with ball milling wereused to prepare BaTiO₃/CoFe₂O₄core-shell structure, then the coated nanoparticleswere sintered to composite ceramics. Comparing to conventional composite, thecore-shell structure composite ceramic with the same composition exhibits highercompact and uniform. Higher resistivity was obtained, which may be due to stronglyenhanced Maxwell-Wagner interface effect, with core-shell structure greatlyincreasing the coupling interface between the two phases.