Research On Preparation And Properties Of Ni/PZT Magnetoelectric Laminated Composites

The magnetoelectric (ME) laminated composites, which have more superior ME property than single phase ME materials and particle ME composites, are generally laminated magnetostrictive materials with piezoelectric materials by some methods such as bonding and electro-deposition. However, the unavoidable bonding layer or electrodes will reduce the ME coupling and deteriorate the ME response. We have prepared Ni/PZT laminated composites without interlayer by electroless deposition to realize the direct coupling between the phases.The effect of bath temperature on the ME performance of Ni/PZT/Ni laminated composites has been investigated. The electroless deposited Ni layer with smaller grain size is obtained at higher bath temperature and shows higher piezomagnetic coefficient, promoting the ME effect of corresponding laminated composites. The maximum ME voltage coefficient is 1.72 V·cm^-1·Oe^-1 when the bath temperature equals to 365.5 K and the deposition rate of Ni increases with bath temperature. Meanwhile, the subsequent lower annealing temperature is beneficial to obtain the Ni layer with smaller grain size and the corresponding laminated composites display better ME effect, which indicates that the grain size of magnetostrictive phase is a key factor influencing the ME performance of laminated composites.The ME performances of cylindrical Ni/PZT/Ni and Ni/PZT laminated composites have also been investigated. The ME voltage coefficient and electromechanical resonance frequency increase as the magnetostrictive-piezoelectric phase thickness ratio increases. The maximum ME voltage coefficient of the cylindrical Ni/PZT/Ni laminated composites is 3.26 V·cm^-1·Oe^-1, which is much higher than that of the plate laminated composite with the same thickness ratio due to the addition of piezoelectric mode of d₃₃. Compared to the Ni/PZT/Ni structure with the same thickness ratio, the cylindrical Ni/PZT laminated composites show better ME performance both in axial and vertical modes because of the larger stress in the PZT layer of the Ni/PZT structure. In addition, the axial ME voltage coefficient increases linearly with the magnetic field when the bias magnetic field is quite large due to electromagnetic induction.Electroless deposition is an excellent method to fabricate ME laminated composites in which the coupling between the magnetostrictive and piezoelectric phases is direct. Moreover, it is convenient to prepare thick films on various substrates of complex shapes by electroless deposition. These are all the foundation of future design and application of ME devices.