Evaluation of piezoelectric material properties for a higher power output from energy harvesters with insight into material selection using a coupled piezoelectric-circuit-finite element method

Piezoelectric material properties have substantial influence on electrical power output from piezoelectric energy harvesters (PEHs). Understanding their influences is the first step in designing effective PEHs to generate higher power outputs. This paper uses a coupled piezoelectric-circuit-finite element method to study the power outputs of different types of piezoelectric materials, including single crystal, polyvinylidene fluoride (PVDF), and soft and hard lead zirconate titanate (PZT) materials. The purpose of this study is to try to gain an understanding of which piezoelectric material property- the elastic compliance s₁₁, the piezoelectric strain constant d₃₁, the piezoelectric stress constant g₃₁, and the relative dielectric constant ε_r33^T, and the associated material properties of the d₃₁ × g₃₁, called the figure of merit (FOM), and the coupling coefficient k₃₁-dominates the power output. A rectangular piezoelectric plate under a low-frequency excitation is used to evaluate piezoelectric material properties for a higher power output. It was found that 1) d₃₁ is a more dominant material property over other material properties for higher power output; 2) FOM was more linearly related to the power output than either the k₃₁ or the d₃₁; and 3) ε_r33^T had some role; when the materials have an identical d₃₁; a lower ε_r33^T was preferred. Because of unexplained outliers, no single material parameter was able to be recommended as selection criteria, but combined FOM with d₃₁ parameters is recommended for selection of piezoelectric material for a higher power output from PEHs.