Soft and Hard Piezoelectric Ceramics and Single Crystals for Random Vibration Energy Harvesting

Abstract

Vibration‐based energy harvesting for enabling next‐generation self‐powered devices is a rapidly growing research area. In real‐world applications, the ambient vibrational energy is often available in non‐deterministic forms rather than the extensively studied deterministic scenarios, such as simple harmonic excitation. It is of interest to choose the best piezoelectric material for a given random excitation. Here, performance comparisons of various soft and hard piezoelectric ceramics and single crystals are presented for electrical power generation under band‐limited off‐resonance and wideband random vibration energy‐harvesting scenarios. For low‐frequency off‐resonance excitation, it is found that soft piezoelectric ceramics based upon lead zirconate titanate (e.g., PZT‐5H and PZT‐5A) outperform their hard counterparts (e.g., PZT‐4 and PZT‐8), and likewise soft single crystals based upon lead magnesium niobate and lead titanate as well as PZT (e.g., PMN‐PT and PMN‐PZT) outperform the relatively hard ones (e.g., manganese‐doped PMN‐PZT‐Mn). Overall, for such off‐resonance random vibrations, PMN‐PT is the most suitable choice among the materials studied. For wideband random excitation with a bandwidth covering the fundamental resonance of the harvester, hard piezoelectric ceramics offer larger power output compared to soft ceramics, and likewise hard single crystals produce larger power compared to their soft counterparts. Remarkably, a hard piezoelectric ceramic (e.g., PZT‐8) can outperform a soft single crystal (e.g., PMN‐PT) for wideband random vibration energy harvesting.

Piezoelectric Energy Harvesting Design Principles for Materials and Structures: Material Figure‐of‐Merit and Self‐Resonance Tuning

“…To identify the FOM of this PEH, four soft and hard piezoelectric ceramics and three soft and hard piezoelectric single crystals were used. [125] The piezoelectric properties of these piezoelectric materials were reported, and nickel and brass were used as the electrode and substrate of the PEH, respectively. [125] The expected value of the electrical power output E[P(t)] (i.e., the averaged electrical power) of this bimorph PEHs is given as follows: [125]…”

“…The FOM of the 31‐mode type‐II cantilevered‐bimorph PEHs operating at an off‐ and on‐resonance frequency were studied using simulations. [ 125 ] Figure a shows the schematic diagram of the cantilevered‐bimorph PEH used for the calculating the output power. [ 125 ] Because the piezoelectric ceramics and metal plate are clamped into the exciter, this bimorph PEH is considered to be a type‐II PEH.…”

“…2 × values, respectively. [125] Therefore, soft-piezoelectric material is good for these PEHs operating at an off-resonance frequency. However, piezoelectric materials, which have both good soft and hard piezoelectric properties, are suitable for PEHs operating at the resonance frequency.…”

Comparison and Scaling Effects of Rotational Micro‐Generators using Electromagnetic and Piezoelectric Transduction

“…Due to the fact that the calculation is conducted using specific design parameters, the figure shows the general trend of performance variations for different types. Given that there are different designs and material properties available, [52] the boundaries shown in this figure cannot be used as a universal criteria for determining the best design for a particular dimension and frequency region.…”

A Comparison Study of Fatigue Behavior of Hard and Soft Piezoelectric Single Crystal Macro-Fiber Composites for Vibration Energy Harvesting

“…Regarding the materials selection, depending on the excitation stimuli (frequency and acceleration), two kinds of piezoelectric materials—soft- and hard-type materials—have been widely utilized in harvesting applications [20,21,22]. In general, soft type piezoelectric materials exhibit higher piezoelectric coefficients and elastic compliances, which are more suitable for off-resonance excitations, whereas the hard type piezoelectric materials generate larger output power under resonant excitations owing to their larger mechanical quality factor.…”