Dae-Yong Jeong

Current Status of Magnetoelectric Composite Thin/Thick Films

Here we review the current status of magnetoelectric (ME) multiferroics and ME composite thin/thick films. The magnitude of ME coupling in the composite systems is dependent upon the elastic coupling occurring at the interface of piezoelectric and magnetostrictive phases. The multiferroic ME films in comparison with bulk ME composites have some unique advantages and show higher magnitude of ME response. In ME composite films, thickness of the films is one of the important factors to have enough signal. However, most of all reported ME nanocomposite structured films in literature are limited in overall thickness which might be related to interface strain resulting from difference in thermal expansion mismatch between individual phases and the substrate. We introduced noble ME composite film fabrication technique, aerosol deposition (AD) to overcome these problems. The success in AD fabrication and characterization of ME composite films with various microstructure such as 3-2, 2-2 connectivity are discussed.

Magnetoelectric properties and magnetomechanical energy harvesting from stray vibration and electromagnetic wave by Pb(Mg1/3Nb2/3)O3-Pb(Zr,Ti)O3 single crystal/Ni cantilever

Magnetoelectric (ME) rectangular unimorph cantilever beam structures of piezoelectric Pb(Mg1/3Nb2/3)O3-Pb(Zr,Ti)O3 (PMN-PZT) single crystal on magnetostrictive Ni plate was designed with ⟨001⟩ and ⟨011⟩-cut crystallographic directions and investigated their ME response and mechanical vibration based energy harvesting behavior. Both magnetoelectric (ME) voltage coefficient (αME) and mechanically harvested power output was found to be strongly dependent on the crystallographic cut directions of PMN-PZT single crystals. The maximum αME and power output of 7.28 V/cm Oe and 1.31 mW was observed for ⟨011⟩ PMN-PZT/i unimorph ME structure at resonance mode under 0.7 G acceleration. The ⟨011⟩ PMN-PZT single crystal showed that in-plane anisotropic behavior, i.e., d31 and d32 significantly affect to the magnitude of αME and harvested power output.

Enhancement of resonant and non-resonant magnetoelectric coupling in multiferroic laminates with anisotropic piezoelectric properties

Giant transverse magnetoelectric voltage coefficients |αE| = 751 and 305 V/cmOe at two electromechanical antiresonance frequencies are found in the symmetric metglas/[011]-oriented 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 crystal/metglas laminate. Unique torsional and diagonal vibration modes are identified to be responsible for those giant |αE| values. Moreover, αE is found to be anisotropic depending on the in-plane magnetic field directions, making the piezoelectrics with anisotropic planar piezoelectricity potentially useful base materials for multi-frequency, phase-sensitive magnetoelectric devices.

Colossal magnetoelectric response of PZT thick films on Ni substrates with a conductive LaNiO3 electrode

We have characterized the magnetoelectric (ME) properties of Pb(ZrTi)O3/LaNiO3/Ni (PZT/LNO/Ni) composites, which are fabricated using aerosol deposition. LNO acted as the bottom electrode for the PZT film and could effectively transfer the stress generated through the magnetostrictive effect of Ni into the piezoelectric PZT film. The PZT/LNO/Ni ME structure exhibits an ME coefficient αE31 = 1Vc m −1 Oe −1 at a very low bias magnetic field of 30 Oe and shows 8.5 V cm −1 Oe −1 at a magneto-mechanical resonance frequency of 204 kHz corresponding to the Ni substrate. These huge ME coefficients are attributed to the improved coupling between the magnetostrictive Ni layer and the piezoelectric PZT thick film via the LNO layer, which is possible due to similar mechanical impedances of Ni, LNO and PZT.

Magneto-Mechano-Electric (MME) Energy Harvesting Properties of Piezoelectric Macro-fiber Composite/Ni Magnetoelectric Generator

Abstract Asymmetric and symmetric magnetoelectric (ME) laminates structures of piezoelectric macro-fiber composite (MFC)/nickel (Ni) were fabricated and investigated their ME and magneto-mechano-electric (MME) energy harvesting responses to an applied magnetic/mechanical stimulations. Both the structures strongly revealed the dependence of ME voltage coefficient (αME) on applied magnetic field directions with an important feature of a zero-bias field ME response. This is much more beneficial for designing the magnetic field sensors. The fabricated MFC/Ni structures exhibited good energy harvesting response to applied simultaneous magnetic/mechanical vibrations of lab magnetic stirrer. The electric power was successfully harnessed from magneto-mechanical stimulations; the resulting potential and power were up to ~20 Vp–p and ~6 μW respectively, which are quite enough power to light a commercial red LED with traditional rectifier circuit and capacitor. Hence, the present MFC/Ni ME generators provide their future feasibility having self-biasing feature for designing the magnetic field sensors as well as for powering small consumer electronic devices and wireless sensor network systems by exploiting mechanical/magnetic stimulations from surrounding.

Enhanced magnetic energy harvesting properties of magneto-mechano-electric generator by tailored geometry

By tailoring the truncated shape of a cantilever structured magneto-mechano-electric (MME) generator that is composed of a piezoelectric single crystal fiber composite and a magnetostrictive Ni plate, a superior output harvesting power density of over 680% was obtained as compared to a typical rectangular shaped generator. The effect of the MME generators shape on the strain distribution induced by magnetostriction and vibration characteristics and harvesting properties were simulated by finite element analysis modeling and confirmed experimentally, respectively. The truncated shape was effective for not only utilizing a more uniform in-plane strain distribution in the active piezoelectric area but also magnifying the flexural vibration amplitude, which in turn can make the generator more powerful under tiny magnetic oscillations.

Dielectric and electrocaloric responses of Ba(Zr 0.2 Ti 0.8 )O 3 bulk ceramics and thick films with sintering aids

Large electrocaloric effect (ECE) has been reported in Ba(Zr0.2Ti0.8)O3 (BZT) bulk ceramics near room temperature. The finding opens up opportunities for developing high performance EC ceramic based refrigeration. To further reduce the operating voltage and enhance the reliability of such EC material, we investigate synthesis of BZT thick films can be fabricated into multilayer EC modules using the commercial multilayer ceramic capacitor (MLCC) technology. However, the high (1450 °C) sintering temperature of BZT EC ceramics poses challenge for the MLCC with low-cost electrodes. This paper investigate sintering aids that can significantly reduce sintering temperature of BZT ceramics. The bulk and thick-film BZT with 1 wt% PbO and B2O3 were sintered at 1200 °C and exhibited high dielectric constant and low loss around room temperature. Dielectric and electrocaloric responses of thus fabricated BZT thick films are studied. The low temperature sintered BZT thick films with proper sintering aids exhibit high breakdown field and larger ECE than the bulk BZT, thus paving the way for the future transition to EC MLCC suitable for EC cooling systems.

Energy storage properties of nano-grained antiferroelectric (Pb,La)(Zr,Ti)O 3 films prepared by aerosol-deposition method

Antiferroelectric films of Sn doped Lead Lanthanum Zirconate-Titanate [(Pb, La)(Sn, Zr, Ti)O₃, Sn-PLZT] with nano-grains were fabricated by aerosol-deposition (AD). The AD process produced highly dense films without visible pores. The polarization-electric field hysteresis loop and the phase transition behavior of PLZT with Sn doping into the B-sites were characterized. The grain sizes of the AD Sn-PLZT films, which were on the nano-scale, were controlled by the annealing temperature. Regardless of the compositions, the films with the nano-grains by the AD process showed less hysteretic behavior and larger stored energy. The Pb_0.97La_0.02(Zr_0.85Sn_0.13Ti_0.02)O₃ (PL-0.13) film deposited by AD and annealed at 750 °C for 1 h showed an energy storage capacity and efficiency of 13.0 J/cm³ and 78.9 %, respectively.

Effect of Microstructure on Magnetoelectric Properties of 0.9Pb(Zr0.52Ti0.48)O3?0.1Pb(Zn1/3Nb2/3)O3 and Ni0.8Zn0.2Fe2O4 Particulate Composites

The effects of magnetostrictive particle distribution on magnetoelectric (ME) properties were investigated in a 3–0 ME composite made of piezoelectric [0.9Pb(Zr0.52Ti0.48)O3–0.1Pb(Zn1/3Nb2/3)O3 + 0.005Mn; PZT–PZN] and 20 wt % magnetostrictive (Ni0.8Zn0.2Fe2O4; NZF) materials. X-ray diffraction (XRD) analysis and energy dispersive X-ray spectroscopy (EDS) results showed that PZT–PZN and NZF did not react with each other and coexisted without severe inter-diffusion. The larger interface area due to the smaller particle size offered greater Fe3+ diffusion into the piezoelectric PZT–PZN, which increased the piezoelectric mechanical quality factor of the 3–0 composite. In addition, the ME property (dE/dH) was also enhanced by the smaller NZF particle size, and this enhancement was attributed to the magnetically induced, homogeneous stress field exerted by NZF onto PZT–PZN.

Exceeding milli-watt powering magneto-mechano-electric generator for standalone-powered electronics

In contrast to typical magnetic energy generators that use electromagnetic induction, which are bulky and have low generation efficiency under small magnetic fields at low frequency, magneto-mechano-electric (MME) generators utilizing the magnetoelectric (ME) coupling effect and magnetic interactions are considered promising candidates. MME generators will serve as a ubiquitous autonomous energy source converting stray magnetic noise to useful electric energy for applications in wireless sensor networks (WSN) for the Internet of Things (IoT) and low-power-consuming electronics. The key component in a MME generator is the ME composite consisting of piezoelectric and magnetostrictive materials, which elastically couples the electric and magnetic behaviour of the respective constituent. Here, we report a MME generator consisting of a crystallographically oriented Pb(Mg1/3Nb2/3)O3–Pb(Zr,Ti)O3 piezoelectric single crystal macro-fibre composite and a highly textured magnetostrictive Fe–Ga alloy, which exhibits an exceptionally high rectified DC output power density of 3.22 mW cm−3. The large energy generation in this structure is ascribed to the coupling between the strong anisotropic properties of the piezoelectric single crystal fibres and textured Fe–Ga magnetostrictive alloy. A smart watch with IoT sensors was driven by the MME generator under a 700 μT magnetic field.