| The primary magnetoelectric (ME) materials become magnetized when placed in an electric field and electrically polarized when placed in a magnetic field. It is an important futuristic, progressive entity for making sensor, processors, actuators and feedback system. In present work, the magnetoelectric composites with PVDF as piezoelectric phase and Ni-Zn ferrites as piezomagnetic phase were prepared and characterized to explore new magnetoelectric materials. Ferrites are structure sensitive materials and their properties critically depend on the preparing method. The formation of Ni-Zn ferrite nanoparticles, its sintered characteristics and β phase formation of PVDF were studied.Ni-Zn ferrites were prepared with the citrate precursor by self-combustion technique, using ferric citrate or ferric nitrate, nickel nitrate, zinc nitrate, citric acid as the starting materials. The results reveal that the grain size of NiZn ferrites powders prepared with sol precursor by the self-combustion technique was normally smaller than that of the powders prepared with gel system by directly sintered method. The mean size of ferrites obtained in the system containing ferric citrate by self-combusted technique was only 16-23nm. The coercive force of NiZn ferrites prepared with the citrate precursor by self-combustion technique was high and the saturation magnetization of the ferrites was low.The sintered density of ferrite pellets obtained from ferric citrate system is larger than that from ferric nitrate system due to smaller particle size obtained from ferric citrate system. The pellets from two systems have the same pure spinel structure according to XRD, but different microstructure from SEM , different dielectric properties and resistivity obtained. Especially, the DC-resistivity (≥109Ω·cm) of the pellets from ferric citrate system is higher than that (≤106Ω·cm) from ferric nitrate system. The DC-resistivity values decrease with increase of sintered temperature. Smaller grains imply larger number of insulating grain boundaries which act asbarriers to the flow of electrons.PVDF film of (3 form was successfully prepared by dip-coating method with N,N-dimethyllforrnarnide(DMF) as solvent. The effects of crystallization temperature and crystallization time on the film's crystallization structure and crystallization degree were examined by XRD and SEM. The optimal process condition to prepare P-PVDF film was determined.The composite film with p-PVDF and Ni-Zn ferrites was successfully prepared by dip-coating method with DMF as solvent and A151 as coupling agent. |
