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Basic Overview of Piezoelectric Materials in Energy Harvesting
Energy harvesting is approaching an interesting technological juncture wherein the power requirements for electronic devices have been reduced while at the same time the efficiency of energy harvesting devices has increased. Out of various
possible energy harvesting technologies, piezoelectric vibration energy harvesting has emerged as a method of choice for powering meso-to-micro scale devices. Piezoelectric materials and transducers can be designed to handle a wide range of input frequencies and forces allowing for energy harvesting to occur.
 During vibration energy harvesting, piezoelectric materials convert mechanical strain into an electrical charge or voltage via the direct piezoelectric effect. The power output of a particular piezoelectric energy harvester depends upon intrinsic and extrinsic factors. Intrinsic factors include the frequency constant of the piezoelectric element, piezoelectric and mechanical properties of the material, and the temperature and stress dependence of the physical properties. Extrinsic factors comprise of the input vibration frequency, acceleration of the base/host structure, and the amplitude of the excitation.
Piezoelectric materials for use in energy harvesting applications can be divided into four different categories: ceramics, single crystals, polymers, and composites. Generally, piezoelectric ceramics are used as the piezoelectric material in energy harvesting devices due to their low cost, good piezoelectric properties, and ease of integration into energy harvesting devices.
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