Structure Effects On The Magnetoelectric Properties Of Magnetoelectric Composites

The laminated magnetoelectric(ME) composites have attracted increasing interest due to their large ME effect at room temperature. To further enhance the ME properties and investigate the factors which affect the ME effect both structures and magnetostrictive materials were optimized. The structure effects on the ME properties of laminated ME composites have been investigated.First, a theoretical model was built to reveal that the ME voltage coefficient relates to the interface coupling parameter. Terfenol-D/PZT multilayer composites were prepared by silver epoxy. Experimentally, the interface defects exist in multilayer composites and the interface energy loss increases with increasing the stacking periodicity. Therefore, the interface coupling parameter decreases, which leads to the gradual decrease of the ME voltage coefficient. Meanwhile, the resonant frequency of Terfenol-D/PZT multilayer composites is independent of the stacking periodicity and agrees well with the predicted one.Secondly, the ME properties in Ni/ PZT/Fe Co laminated composites with different strain modes were also investigated. Ni and Fe Co plates were bonded on the PZT plates with different orders to obtain different strain modes:(i) bending extensional strain(BES);(ii) longitudinal extensional strain(LES);(iii) torsional extensional strain(TES). At optimal DC magnetic field, the highest ME voltage coefficient can be obtained in the TES mode and at the bending and longitudinal resonance frequencies the ME voltage coefficients are 3.97 and 4.23 V/cm Oe, respectively.Lastly, three Ni/PZT/Terfenol-D laminated composites were prepared and bonded to nonmagnetic glass plates to obtain three different mechanical boundary conditions:(i) both ends of sample traction free(F-F),(ii) one end clamped while the other traction free(C-F), and(iii) both ends of sample clamped(C-C). In these three modes, various experimental resonance frequencies appear and agree well with the calculated ones in 1-140 k Hz range. Six resonance frequencies observed in C-F mode may be useful for multifrequency operation and the low resonance frequency can be used to decrease the eddy current loss of the magnetostrictive phase and increase the lifetime of the devices.