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Magnetoelectric (ME) composites have received attention abidingly due to the promising potential applications in magnetic field sensor and energy harvester. In recent years, shear mode ME composite was frequently discussed with promising applications in high-frequency magnetic field with large signal-to-noise ratio. Single-crystal LiNbO3, as a lead-free piezoelectric phase with high mechanical quality factor and small dielectric constant, is suitable for achieving a large shear ME effect with large shear piezoelectric coefficient d15 or d24, and different piezoelectric coefficients can be obtained by crystal-cut transformation. The transformation rule of shear ME coefficient with transformation of LiNbO3 crystal orientation and the MHz high-frequency magnetic detection is still lacking. Furthermore, self-biased ME composite can be obtained with SrFe12O19 ribbon, which is useful for the integration and miniaturization of ME sensor. In the present work, we use a series of X-cut LiNbO3 to obtain different d15 or d16 in a stretch-shear ME composite. Piezoelectric coefficient d15 and ME coefficient E15 of Metglas/LiNbO3 composite are obtained in experiment, respectively. The results show that LiNbO3 xzt/30 has the largest d15 and E15, and the transformation rule of E15 is consistent with the coordinate transformation of d15. The structure of stretch-shear ME composite is optimized to improve the ME coefficient. Then the stretch-shear mode self-biased SrFe12O19/Metglas/LiNbO3 composite is fabricated, and shear ME response is observed under zero external direct current magnetic bias. Moreover, E15 at electromechanical resonance frequency is gained at shear-mode high frequency (0.991 MHz and 3.51 MHz). The largest ME coefficient E15 is acquired in the stretch-shear 5-foil Metglas/LiNbO3 (xzt/30) composite of 134.16 mV/(cmOe) at 1 kHz and 9.17 V/(cm Oe) at 3.51 MHz. This work is beneficial to the confirming of the corresponding rules of shear ME coefficient and LiNbO3 piezoelectric coefficient, showing that the composite possesses the potential applications in integration, miniaturization and high-frequency resonant sensor.

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 E15 as a function of orientation of LiNbO3 shows that the maximum E15 is 235.1 mV/(cmOe) 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 E15 are, respectively, 24.13 V/(cmOe) in the stretch-shear mode Terfenol-D/LiNbO3 and 11.46 V/(cmOe) 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.