Study On The Magnetostrictive/Piezoelectric Magnetoelectric Composites And Magneto-Elasto-Electric Coupling

The magnetoelectric effect is defined as an induced electrical polarization of a material under an applied magnetic field, or an induced magnetization under an external electric field. Magnetostrictive/piezoelectric magnetoelectric composite is a new type of functional materials, which is realized by product effect of composite of magnetostrictive property and piezoelectric property. There has been increasing attention to the magnetoelectric composite. Herein, the preparation, properties characterization, magneto-elasto-electric coupling and application of magnetostrictive/piezoelectric magnetoelectric composites are studied in this dissertation. The main results in the dissertation are as follows:1. The characterization of magnetostrictive/piezoelectric compositesA parameter (FM=λs·μr, where λs is saturation magnetostriction, μr is the relative magnetic permeability, respectively.) is proposed as a figure of merit to characterize the magnetic performance of an magnetostrictive/piezoelectric composites with high magnetoelectric effect. It is found that the induced magnetoelectric output voltage has a good linear response to the applied ac magnetic field in Permendur/Pb(ZrxTi1-x)O3 (PZT) composites, and the magnetoelectric/converse magnetoelectric resonance frequencies are corresponded to the impedance resonance and anti-resonance ones in Terfenol-D/0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (0.72PMN-0.28PT) composites, respectively.2. The effect of uniaxial compressive stress on ferroelectric performance in0.72PMN-0.28PT single crystalIt is experimentally and theoretically found that the uniaxial compressive stress can lead to the decrease of polarization dissipation energy, ferroelectric remanent polarization and the coercive field of <001>-oriented 0.72PMN-0.28PT crystal. A numerical simulation based on a phenomenological Landau-Khalatnikov theory is used to plot the polarization hysteresis loop under stress. The result of numerical simulation agrees with the experimental observation very well. The influence of stress on ferroelectric properties is attributed to the stress-induced decrease in the switchable domains.3. The application of magnetostrictive/piezoelectric composites — H2 detectionA Permendur/PZT drum transducer has been fabricated for H2 detection. Due to the difference in the acoustic wave velocity for H2 (1284 m/s) and air (331 m/s), the resonance frequency of the magnetoelectric coupling effect will shift when H2 gas enters the drum cavity filled with air. A good linear relationship between the resonance frequency shift (Δf) and the volume fraction of H2 (n) is observed. The detection coefficient (Δfln%) for H2 is-0.48 kHz, which is potential to be used in the application of H2 physical detection.4. The application of magnetostrictive/piezoelectric composites — magneto-light deviceClear magneto-light output is obtained from a fabricated three-phase composite of magnetostrictive, piezoelectric, and electroluminescent materials. Increasing the strength of the applied ac magnetic field produces an enhanced magneto-light output. The magneto-light composite has potential applications in optical monitoring of magnetic fields, magnetic/light sensing, and transducer technologies.