Formation And Dielectric,Magnetic Properties Of PVDF/Nickel,Zinc Ferrite Composite Films

The ceramic-polymer ferroelectric-ferromagnetic composite is one of the most important FE-FM composites,which has typical advantages in flexibility and low dielectric loss.Percolation theory is an important theory to prepare high-permittivity composites,while the dielectric loss of the composite near percolation theroshold is always too large,and the magnetical properties will be restricted owing to the exist of the non-magnetical phase if the magnetic particles donnot contact with each other.Thus it’s quite a problem to prepare the composites with high permittivity,low dielectric loss and high magnetic properties.In this work,we proposed PVDF/nickel-zinc ferrite(NZFO)composite,in which NZFO acts as conductive filler due to its much higher conductivity than that of PVDF matrix while it is also applied as ferromagnetic phase.Moreover,in the composite film,the ferrite nanoparticles will be well-enwrapped by dielectric polymer matrix and general problem of relatively high dielectric loss of the percolative system will be most probably overcome.Also,the percolation theroshold will be increased owing to the well-wrapped structure,making the composite’s magnetic properties well-accepted.The main conclusions are listed below.(1)A series of nickel,zinc ferrite with different compostion is prepared by self-combustion reaction,which has typical spinel phase and soft magnetic properties.Pure ferrite is only fabricated for the composition of Ni0.5Zn0.5Fe2O4 as unwilled metal oxides exist in the product for other compositions.(2)The Crystallization of PVDF can be effected by heat-treated temperature and low temperature benefits the crystallization of the polar β phase of PVDF while crystallized from polar solvent,but the addition of NZFO particles can lead to the crystallization of β-PVDF even at high temperatures.(3)The introduction of NZFO particle into PVDF matrix can increase the apparent dielectric constant of the composite.And the permittivity is controlled by the relative high content of β-PVDF,compound law of Kirkpatrick’s model and the series of micro capacitors engineered inside appear respectively in the PVDF/NZFO composite film.It reaches about 74 at 200kHz near threshold which is 20 times higher than that of the film with only pure PVDF,while the dielectric loss still keeps below 0.1 for several hundreds kHz interval.(4)The magnetic properties of the composite which has super high permittivity keeps well acceptable,as the saturation and remnant magnetizations are 42.04 emu/g and the permeability is 3.11,reaching 87%and 64%of those in the single phased NZFO.(5)It is obvious that the PVDF/NZFO prepared here with both high dielectric and excellent magnetic properties may attract us to use as a flexible film with multi-susceptible properties as well as high performance.