High-efficiency piezoelectric energy harvesters of c-axis-oriented epitaxial PZT films transferred onto stainless steel cantilevers

We fabricated piezoelectric energy harvesters composed of c-axis-oriented Pb(Zr,Ti)O(3) (PZT) films transferred onto stainless steel cantilevers for improved energy conversion efficiency and toughness. PZT films were epitaxially grown on Pt/MgO substrates using rf-magnetron sputtering and transferred to 50-mu m-thick stainless steel cantilevers. The transferred PZT films had a low dielectric constant (epsilon(r) = 166) and high transverse piezoelectric coefficient (e(31)* = d(31)/s(11) = -4.5 C/m(2)); these values are almost the same as those of the as-grown epitaxial PZT films on MgO substrates. Because of the small thickness of the cantilever, the first resonant frequency could be as low as 126 Hz without a seismic mass at the tip of the cantilever. At an acceleration of 5 m/s(2), the energy harvester generated an average output power of 5.3 mu W at the optimal load resistance of 50 k Omega. The output power increased monotonically with the acceleration, reaching 244 mu W under an acceleration of 50 m/s(2) without damage to the cantilever. (C) 2010 Elsevier B.V. All rights reserved.