| Magnetoelectric(ME) composite is a kind of new multi-functional materials with excellent ME performance, it has significant ME effect based on the coupled product of piezoelectric effect of the piezoelectric layer and magnetostrictive effect of the piezomagnetic layer. Studies have shown that when the thickness ratio of magnetostrictive layer to piezoelectric layer is 0.3, the ME composite has very significant ME effect. So this paper selected the research object of laminate ME composite with the thickness ratio of 0.3 to simulate its magnetoelectric phase characteristics, and then by studying different shapes of PZT/Terfenol-D laminate ME composite samples to explore the phase characteristics in ME effect, especially focus on exploring the origin of the phase shift under resonant frequency. It theoretically explains the existing experimental phenomenon of magnetoelectric phase increasing π at the resonant frequency very well.First, according to the ME coupling equivalent circuit under special boundary conditions, the expressions of direct/converse ME coefficients are achieved. According to the direct/converse ME coefficient expressions, the modulus of direct/converse ME coefficients and their phase regulations with the change of frequency are calculated, it can be found that ME phase has increased π around the resonant frequency.Second, we explored the direct/converse ME coefficients and their phase regulations with the change of frequency of the strip PZT/Terfenol-D laminate ME composite, finding that whether in direct magnetoelectric effect(DME) or in converse magnetoelectric effect(CME), the peak values of DME/CME coefficients appeared obviously and phases shifted abruptly around the resonant frequency. Further through the method of high-speed dynamic strain-meter we tested the variation of strain and phase with frequency in detail, finding that the strains change with the frequency almost linearly in converse piezomagnetic effect, no obvious peak phenomenon appeared, also the phases did not have any abrupt shift; however in converse piezoelectric effect the strains showed obvious peak values near the resonance frequency of 43 kHz, and correspondingly large phase shift of near π occurred around the resonant frequency. So we confirm the phase shift in CME/DME mainly comes from the contribution of the electromechanical resonance of piezoelectric part. The electromechanical resonance inspires ME resonances and induces DME and CME phase shift of near π; but the piezomagnetic part is difficult to inspire the ME resonance and mainly works as stress transfer and energy conversion between magnetic and mechanical energy in ME resonance.Finally, in order to further verify the conclusion of the experiment above, we changed sample shape and explored the CME/DME coefficients and their phase regulations with the change of frequency of the circular PZT/Terfenol-D laminate ME composite; then like the experiment method above, we detailedly tested the variation of strain and phase with frequency through the method of high-speed dynamic strainmeter. After testing we found that the test results under the same test condition is completely similar as the results of the strip ME composite. Therefore it demonstrated the regulation of the origin of phase shift more powerfully.This finding is helpful for the design of ME device, such as sensor, transducer, oscillator and so on. With the development of miniaturization of device, the demand for multi-functional magnetoelectric composite materials will become larger and larger, so its trend of development is very good. The magnetoelectric phase change by a large margin under resonance frequency is expected to become a new kind of phase modulation technique, which has great potential application value. |
