Research On The Influencing Factors Of The Magnetic Capacitance Of The Magnetoelectric Composite Vibrator

Magnetoelectric capacitance(MC)refers to the change of the dielectric constant of materials with the magnetic field.The magnetocapacitance effect of laminated magnetoelectric composites is a macroscopic interaction.The macroscopic interaction between an external magnetic field and magnetoelectric composites may well be mediated by the stress.The applied magnetic field affects the degree of the piezoelectric distortion via the magneto-mechanical-electric coupling,and the applied magnetic field is expected to indirectly alter the dielectric response.The larger the piezoelectric distortion,the greater will be the change in the dielectric permittivity.The research indicates that there are two main factors influencing the magnetoelectric capacitance effect of laminated composite materials:One is the frequency of the alternating electric fields.When the frequency of the external field is equal to the resonant frequency or the anti-resonant frequency of the piezoelectric vibrator,the high magnetic capacitance effect can be obtained;The other main factor that affect layered composite with a huge magnetocapacitance effect is the polarization direction of the piezoelectric resonator.Past studies have suggested that the L-L magnetoelectric coupling(the direction of magnetization is parallel to the direction of polarization)is significantly higher than the L-T magnetoelectric coupling(the direction of magnetization and polarization are vertical).This paper studies at room temperature of an electric field when the frequency is equal to the resonance frequency of piezoelectric vibrator or the resonant frequency,magnetocapacitance and magnetoimpedance of piezoelectric ceramic PZT and magnetostrictive alloy Terfenol-D laminated composite structures.The specific research contents are as follows:(1)In this paper,L-L and L-T patterns layered composites are designed to study the effect of piezoelectric polarization on the magnetocapacitance of laminated composite structures.From piezoelectric,ferromagnetic constitutive equation,with composite oscillator resonant frequency with the magnetic field changes as the foundation,we use the longitudinal direction of polarization of magnetoelectricity conversion based on the Lorentz harmonic oscillator model and the horizontal polarization of magnetoelectricity conversion good for Debye oscillator model to establish magnetic regulation theory model of piezoelectric capacitance changed with magnetic field,and the magnetocapacitance of the two models of longitudinal polarization and transverse polarization is simulated numerically.The experiment and numerical simulation basically agree.This research establishes the theoretical and experimental basis for the design of magnetic capacitance sensor.(2)The effect of multilayer magnetoelectric composite structure and demagnetization factor on the magnetic coupling of composite materials is studied.Three-layer and five-layer composite structures were designed.The impedance,capacitance and inductance of composite materials are studied with the change of magnetic field,and it is found that the change of the five-layer composite structure impedance is larger and faster.Compared with the three-layer composite structure,the magnetic resolution of the five-layer composite is higher;We also designed the laminar PZT to compound with the rectangular Terfenol-D and the square Terfenol-D,to study the effect of demagnetization factors on magnetoelectric coupling.The experimental results show that,the demagnetization factor is closely related to the saturation magnetic field of impedance,inductance and capacitance,which provides a theoretical and experimental basis for the design of magnetic field sensors with low magnetic field detection.