The Effect Of Magnetic Field Assisted Heat Treatment On The Properties Of PVDF Based Magnetoelectric Composites

Magnetoelectric composites have been widely used in magnetic field sensors,memories and energy storage devices.In practical application,their magnetoelectric coefficients are generally required to be high enough.The results show that the magnetoelectric coefficient can be improved by optimizing the microstructures of magnetoelectric composites.PVDF based MC were chosen as the subject investigated,and the magnetic field assisted heat treatment process was used to control the microstructures of composites during the preparation of magnetoelectric composites.In this paper,the effects of the content of lead zirconate titanate（PZT）and rare earth alloy（Terfenol-D）（TD）on the electrical properties of 0-3 type PVDF/PZT/TD magnetoelectric composites were investigated.The experimental results show that when the volume ratio of PVDF/PZT/TD is 30:63:7,the piezoelectric constant is 31.2pC/N,and the magnetoelectric coefficient reaches the maximum value 45.75mV·cm^-1·Oe^-1at the resonance frequency of 87kHz.In order to further improve the magnetoelectric coefficient of the magnetoelectric composites,the magnetic field assisted heat treatment process was used in the preparation of magnetoelectric composites,the effect of external magnetic field on the electric properties of MC were investigated.The results show that with the increase of the magnetic field,the magnetoelectric coefficient increases first and then decreases,when the magnetic field is 200Oe,the maximum magnetoelectric coefficient is71.46mV·cm^-1·Oe^-1,which is 50%higher than that without magnetic field.In order to improve the content of TD in 0-3 magnetoelectric composites,the structure of the composite was improved.The（TD+PVDF）/（PZT+PVDF）/（TD+PVDF）（TPT）magnetoelectric composites with layer thickness ratio of 2:3:2 were prepared.The results show that theα_ME of layered magnetoelectric composites is 2556.61mV·cm^-1·Oe^-1,which is30 times higher than that of 0-3 type magnetoelectric composites.Then the magnetic field heat treatment is used in hot pressing process,the results show that with the increase of the magnetic field,the magnetoelectric coefficient increases first and then decreases,when the magnetic field is 300Oe,it reaches the maximum value of 3051.67mV·cm^-1·Oe^-1,which is 19%higher than that without magnetic field.Finally,the piezoelectric properties of TPT layered magnetoelectric composites were optimized by adding an appropriate amount of CoFe₂O₄.The experimental results show that when the content of CoFe₂O₄ is 0.8vol%,the piezoelectric constant reaches the maximum value of 36.8pC/N,which is increased by 29%compared with that without CoFe₂O₄.The magnetic field assisted heat treatment process is also applied to this magnetoelectric composites.Results show that with the increase of the magnetic field,the piezoelectric coefficient increases slightly and the magnetoelectric coefficient first increases and then decreases.When the magnetic field is 300Oe,it reaches the maximum value of 3180.26mV·cm^-1·Oe^-1,which is 17%higher than that without magnetic field.The improvement of the structure and the magnetic field assisted heat treatment process are helpful to the improvement of the magnetoelectric properties.This work has guiding significance for the magnetoelectric properties of magnetoelectric composites controlled by magnetic field and the preparation of the high performance magnetoelectric composites.