Magnetoelectric vibrational energy harvester utilizing a phase transitional approach
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Research Letter
Magnetoelectric vibrational energy harvester utilizing a phase transitional approach Margo Staruch , U.S. Naval Research Laboratory, Washington, DC 20375, USA Jin-Hyeong Yoo, and Nicholas Jones, Physical Metallurgy and Fire Protection Branch, Carderock Division, Naval Surface Warfare Center, Bethesda, MD 20817, USA Peter Finkel, U.S. Naval Research Laboratory, Washington, DC 20375, USA Address all correspondence to Margo Staruch at [email protected] (Received 27 August 2018; accepted 8 November 2018)
Abstract A broadband magnetoelectric energy harvester, consisting of Fe1−xGax (Galfenol) as the magnetostrictor and a relaxor ferroelectric single crystal as the piezoelectric, has been designed and optimized. Finite element analysis (FEA) has been employed to show that either a linear displacement or a 180° rotation of a magnet is sufficient to achieve maximum stroke from the Galfenol rod, which induces a rhombohedral to orthorhombic phase transition in Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 that produces a large jump in voltage. A rotational design based on a pendulum with an unbalanced mass was fabricated and used to confirm the validity of our FEA model.
Introduction Over the past several decades, there has been considerable interest in converting mechanical energy into electrical energy. This can be achieved through engineered electrostatic or electromagnetic systems, as well as with piezoelectric materials.[1–4] Although electromagnetic induction is promising for large-scale applications, piezoelectrics are generally considered the best candidates for small-scale devices, such as microelectromechanical systems, while maintaining useful output power. Most current technologies, however, are based on cantilevers, where the power is maximized at the resonant frequency, and achieving a broadband vibrational energy harvester has been elusive thus far. Previous works have attempted to flatten the frequency dependence of the power output by developing an array of cantilevers with different lengths, and therefore resonance frequencies,[5] tuning the dimensions of a novel cantilever design to move two different resonant modes closer,[6,7] or utilizing non-linear oscillations through a magnetic tip mass with two bi-stable states.[8,9] One other promising candidate, recently under development, is the use of an induced phase transition in relaxor ferroelectric single crystals of Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN-PMN-PT). By applying a pre-stress close to the critical stress for the phase transition, the power density of the single crystal is on par with that of other materials operating under resonance, while the energy density per cycle is two orders of magnitude (∼100×) larger than linear piezoelectric materials.[10,11]
Another active area of development of vibrational energy harvesters is a move toward magnetoelectric (ME) composites, consisting of piezoelectric and magnetostrictive phases coupled through strain. The addition of the magnetostrictive component has been shown to enhance
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