Huaduo Shi

Colossal low-frequency resonant magnetomechanical and magnetoelectric effects in a three-phase ferromagnetic/elastic/piezoelectric composite

Colossal low-frequency resonant magnetomechanical (MM) and magnetoelectric (ME) coupling effects have been found in a three-phase composite made of Pb(Zr,Ti)O3 ceramic fibers/phosphor copper-sheet unimorph and NdFeB magnets. The experimental results revealed that the ferromagnetic/elastic/piezoelectric three-phase composite with a cantilever beam structure could show huge bending MM coefficient of ∼145.9 × 10−3/Oe (unit in bending radian per Oe) and ME voltage coefficient of ∼16 000 V/cm·Oe at the first-order bending resonance frequency of ∼5 Hz. The achieved results related to ME effect are at least one order of magnitude higher over those of other ME materials and devices reported ever. The extremely strong MM and ME couplings in the three-phase composite are due to strong magnetic force moment effect induced by the interaction between NdFeB magnets and the applied magnetic field, and further resonant enhancement via the strain-mediated phosphor copper-sheet with a relatively high mechanical quality factor.

Enhanced Resonance Magnetoelectric Coupling in (1‐1) Connectivity Composites

Bulk-magnetoelectric (ME) composites consisting of various piezoelectric and piezomagnetic materials with (3-0), (3-1), (2-2), and (2-1) connectivity are proposed in a bid to realize strong ME coupling for next-generation electronic-device applications. Here, 1D (1-1) connectivity ME composites consisting of a [011]-oriented Pb(Mg,Nb)O3 -PbTiO3 (PMN-PT) single-crystal fiber laminated with laser-treated amorphous FeBSi alloy (Metglas) and operating in L-T mode (longitudinally magnetized and transversely poled) are reported, which exhibit an enhanced resonant ME coupling coefficient of ≈7000 V cm-1  Oe-1 , which is nearly seven times higher than the best result published previously, and also a superhigh magnetic sensitivity of 1.35 × 10-13 T (directly detected) at resonance at room temperature, representing a significant advance in bulk magnetoelectric materials. The theoretical analyses based on magnetic-circuit and equivalent-circuit methods show that the enhancement in ME coupling can be attributed to the reduction in resonance loss of laser-treated Metglas alloy due to nanocrystallization and the strong magnetic-flux-concentration effect in (1-1) configuration composites.

A magnetoelectric flux gate: new approach for weak DC magnetic field detection

The magnetic flux gate sensors based on Faraday’s Law of Induction are widely used for DC or extremely low frequency magnetic field detection. Recently, as the fast development of multiferroics and magnetoelectric (ME) composite materials, a new technology based on ME coupling effect is emerging for potential devices application. Here, we report a magnetoelectric flux gate sensor (MEFGS) for weak DC magnetic field detection for the first time, which works on a similar magnetic flux gate principle, but based on ME coupling effect. The proposed MEFGS has a shuttle-shaped configuration made of amorphous FeBSi alloy (Metglas) serving as both magnetic and magnetostrictive cores for producing a closed-loop high-frequency magnetic flux and also a longitudinal vibration, and one pair of embedded piezoelectric PMN-PT fibers ([011]-oriented Pb(Mg,Nb)O3-PbTiO3 single crystal) serving as ME flux gate in a differential mode for detecting magnetic anomaly. In this way, the relative change in output signal of the MEFGS under an applied DC magnetic anomaly of 1 nT was greatly enhanced by a factor of 4 to 5 in comparison with the previous reports. The proposed ME flux gate shows a great potential for magnetic anomaly detections, such as magnetic navigation, magnetic based medical diagnosis, etc.

A flexible, wave-shaped P(VDF-TrFE)/metglas piezoelectric composite for wearable applications

In this work, a wave-shaped piezoelectric composite (WSPC) made of fine β-phase vinylidene fluoride trifluoroethylene copolymer (P(VDF-TrFE)) polymer and high-elastic FeSiB amorphous alloy (metglas) ribbon has been successfully fabricated for wearable device applications. X-ray diffraction and the Fourier Transform Infrared Spectrum studies reveal P(VDF-TrFE) exhibiting the fine β-phase. Both theoretical analysis and experimental results show that unique wave-shaped structure enhances the electromechanical coupling significantly, because of the combination piezoelectric effects of d33 and d31 modes in P(VDF-TrFE) polymer, as well as the enhanced effective piezoelectric coefficient caused by the pre-stretch in P(VDF-TrFE) film. Two application examples of WSPC, (i) mechanical force sensor or energy harvester, and (ii) the medical blood-pressure pulse sensor, have been investigated, which show that the WSPC is a promising candidate for future wearable device applications.

A piezoelectric pseudo-bimorph actuator

We report a piezoelectric pseudo-bimorph actuator, which is made of only one single plate with interdigitated electrodes on both sides and polarized alternately in longitudinal direction. Like a bimorph actuator, it can also produce a large bending actuation based on anti-symmetrically longitudinal piezoelectric d33 strain effect under an applied electric field. The presented pseudo-bimorph actuator shows much better temperature stability than conventional piezoelectric bimorph actuators from room temperature to the depolarization temperature of the material due to lacking of interface strain loss.

Converse magnetoelectric effect in laminated composite of Metglas and Pb(Zr,Ti)O3 with screen-printed interdigitated electrodes

In this study, we investigate the converse magnetoelectric (CME) effect in a laminated composite consisting of Metglas ribbons and Pb(Zr,Ti)O3 (PZT) plate with screen-printed interdigitated electrodes and operating in longitudinal magnetization and longitudinal polarization (L-L) mode. Large CME coefficients of 0.134 G·cm/V at frequency of 1 kHz and 2.75 G·cm/V at resonance frequency of 43.5 kHz under a small bias magnetic field of 7 Oe are achieved. The large CME effect can be attributed to the L-L mode and low mechanical loss of the Metglas/PZT laminated composite.

A digitally linear piezoelectric bimorph actuator in open-loop mode

The current paper reports a digital piezoelectric bimorph actuator having segmented electrodes and producing 2 to the nth power digital bending actuation in on/off switch mode and under a fix applied voltage. Correspondingly, a simple model for predicting digital actuation under applied coding voltage is also presented. Experimental results have confirmed that the proposed actuator can produce a linear digital displacement without a hysteresis loop. The proposed method is significant for open-loop high precise actuation.

Magnetoelectric coupling of a magnetoelectric flux gate sensor in vibration noise circumstance

A magnetoelectric (ME) flux gate sensor (MEFGS) consisting of piezoelectric PMN-PT single crystals and ferromagnetic amorphous alloy ribbon in a self-differential configuration is featured with the ability of weak magnetic anomaly detection. Here, we further investigated its ME coupling and magnetic field detection performance in vibration noise circumstance, including constant frequency, impact, and random vibration noise. Experimental results show that the ME coupling coefficient of MEFGS is as high as 5700 V/cm*Oe at resonant frequency, which is several orders magnitude higher than previously reported differential ME sensors. It was also found that under constant and impact vibration noise circumstance, the noise reduction and attenuation factor of MEFGS are over 17 and 85.7%, respectively. This work is important for practical application of MEFGS in real environment.