厚度剪切模式铌酸锂基复合材料的磁电性能优化

Optimization of magnetoelectricity in thickness shear mode LiNbO_3/magnetostrictive laminated composite

通过弹性力学方法计算了基于厚度剪切模式的铌酸锂(LiNbO_3)基磁电复合材料磁电系数与铌酸锂晶体切型、磁致伸缩材料种类、材料尺寸的关系,并讨论了两种不同复合结构边界条件对剪切磁电性能的影响.计算结果表明:(xzt)30°切型铌酸锂单晶具有最大剪切压电系数dp15,制作成的复合材料具有最大剪切磁电系数αE15;通过两相尺寸优化,伸缩-剪切模式Terfenol-D/LiNbO_3复合材料最大剪切磁电系数为24.13 V/(cm·Oe),剪切-剪切模式Metglas/LiNbO_3复合材料最大剪切磁电系数为11.46V/(cm·Oe).实验结果与理论计算规律相符,研究结果为剪切磁电复合结构的设计、剪切模式铌酸锂切型的选择优化提供了指导,有望利用高机械品质因数Q_m值的铌酸锂单晶设计高频谐振磁场探测器.

Magnetoelectric（ME） composites have recently attracted much attention and triggered a great number of research activities,owing to their potential applications in sensors and transducers.Many researches have focused on the enhancement of ME coefficient by choosing suitable composite material and vibration mode based on the coupling between stress and strain.Besides normal stress,another vibration mode,shear mode,is further discussed as a potential high-frequency resonant device for a high frequency magnetic field detector,and it is useful to optimize the shear ME coefficient to broaden the application scope of the compositions.In this paper,an elasticity method is used to calculate ME coefficients of thickness shear mode LiNbO3/magnetostrictive laminated composites for various crystal orientations of LiNbO3,magnetostrictive materials and material sizes.The stretch-shear structure and shear-shear modes of the composite with considering the boundary condition are both discussed and further optimized.According to the structure design of stretch-shear mode composite from the literature,we design a new structure to achieve the uniform and pure shear ME effect,which changes the magnetostrictive phase on the bonding part into rigid material to avoid stretch deformation.We find that in the shear-shear ME composite,the structure should not move in the in-plane direction in order to realize the parallelogram deformation under shear stress,but should be free in the thickness direction to meet the change of thickness with shear deformation.For the stretch-shear mode Metglas/LiNbO3[（xzlt）x°/y°],the shear ME coefficient αE15 as a function of orientation of LiNbO3 shows that the maximum αE15 is 235.1 mV/（cm·Oe） when x=0 and y=30.The results indicate that optimal shear ME coefficient is obtained at（xzt）30°LiNbO3,resulting from the maximum shear piezoelectric coefficient dp15.By changing the material size in stretch-shear composite,the shear ME coefficient increases with the increase of thickness of magnetostrictive phase,because the stretch force increases with the increase of the cross-sectional area of magnetostrictive phase.The maximum values of αE15 are,respectively,24.13V/（cm·Oe）in the stretch-shear mode Terfenol-D/LiNbO3 and 11.46 V/（cm·Oe） in the shear-shear mode Metglas/LiNbO3 by the optimization of material sizes.Experimental results are in accordance with calculation results.It is confirmed that LiNbO3（xzt） 30° is the best choice for achieving the largest shear ME effect,and thicker Terfenol-D can help to achieve a larger ME coefficient in this stretch-shear composite.This work provides a design method to choose the structure and crystal orientation of shear LiNbO3-based ME laminated composite,which shows a prospect of applications in high-mechanical-quality factor Qm and high-frequency magnetic detectors with shear resonant devices.