| Multiferroic materials that simultaneously display ferroelectricity, ferromagnetism, and ferroelasticity as well as coupling among them, have been widely investigated due to their potential applications in magnetic sensors, multi-state storage and electrically controllable microwave devices. Magnetoelectric (ME) effect, as one of the important features of multiferroic materials, have recently become a research subject of intense interest due to their theoretical and practical significance. The direct magnetoelectric (DME) effect is defined as a variation of polarization in response to an applied magnetic field, and the converse magnetoelectric(CME) effect is defined as a variation of magnetization in response to an applied electric field.Two-phase ME composite has much higher ME coupling coefficient than single-phase ME material and is of simple fabricating process, which make it attract extensive research interests. Two-phase ME composite usually consists of ferromagnetic and ferroelectric ceramics with various connective architectures. The common connective architectures are zero to three dimensions (0-3), two to one dimensions (2-1), two to two dimensions (2-2) and so on. In addition, some new coupling modes have been developed in recent years, such as magneto-torque-electric composites, which has attracted much attention due to its colossal magnetoelectric effect.This article focus on the research of direct and converse magnetoelectric effect of 2-2 type magnetoelectric composite, magneto-torque-electric effect of ferromagnetic-elastic-piezoelectric (FEP) composite, and make some exploration in device applications. The main contents are as follows:1. A lead free magnetoelectric (ME) laminate composite consisting of polarized piezoelectric ceramic of 0.95(K0.5Na0.5)Nb0.96Sb0.02Ta0.02O3-0.05(Bi0.5K0.5)ZrO3 (KNNST-BKZ) and magnetized magnetostrictive Metglas have been fabricated and its ME properties have been evaluated. Under the resonant frequency, the magnetoelectric coupling coefficient reaches up to 7.85 V/cm·Oe. This result suggests the lead-free KNNST/BKZ/Metglas layered composite has the promising prospect in application of devices.2. The non-magnetostrictive ME effect was realized in a simple ferromagnetic-elastic-piezoelectric (FEP) composite. The FEP composite comprised two piezoceramic Pb(Zr,Ti)O3 (PZT) plates and NdFeB magnets elastically coupled by a cantilever beam made of phosphor copper-sheet. The effects of the beam length on the ME coefficient as a function of frequency and the linear relationship between the ME voltage output and the applied magnetic field at the resonant frequency were experimentally investigated. A notably superior ME coefficient of 3800 V/cm-Oe at extremely low resonant frequency of 5.524 Hz was obtained for the FEP composite with the beam length of 8 cm. The quasi-static ME coefficients for the FEP composites with different beam lengths are all of the same value of 10 V/cm-Oe, which was also theoretically explained. Such a composite structure shows the possibility to obtain a magnetic sensor element with ultrahigh sensitivity in low frequency range. The results provide a comprehensive understanding for the optimal design of FEP composite with high ME coefficient.3.Two different models of CME composites based on Pb(Zr,Ti)O3-bimorph/Metglas(bending model) and screen-printed interdigitated electrodes (IDE) Pb(Zr,Ti)O3/Metglas(Longitudinal-longitudinal model) laminate were studied, which all show enhanced CME effect compared to the homomorphic unimorph/Metglas laminate. Under the same electric field, the converse magnetoelectric coupling coefficient of the Pb(Zr,Ti)O3-bimorph/Metglas and IDE PZT/Metglas laminates are 1.4 and 1.97 times compared with that of the homomorphic unimorph/Metglas one. The experiment results are consistent with the theoretical predictions. This work provide a guiding for the optimal design of CME devices working in low voltage drived bending and longitudinal work mode.4. The possibility of the tunability of inductance was analyzed, and a circular ferrite/piezoelectric.composite inductor was prepared. The results revealed that the inductance has linear response with the electric field. Under 4 kV/cm of the electric field, the inductance tunability reached a value up to 56.7%... |
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