Quantitative evaluation of energy harvesting capabilities on flexoelectric and piezoelectric materials

Piezoelectric and flexoelectric materials have attracted increasing attention for mechanical energy harvesting (EH) in various applications, owing to their simple configuration, easy accessibility, high compatibility, and electro-mechanical conversion efficiency. In order to quantitatively evaluate the EH capability of different types of piezoelectric and flexoelectric materials, a coefficient m is proposed in this work, defined as the ratio of the square of electro-mechanical coupling coefficients and dielectric constant. With this proposed coefficient, we elucidate the underlying mechanism for the reason that polymer, ceramics, and ceramic–polymeric composite materials demonstrate different levels of energy conversion capabilities in piezoelectric and flexoelectric EH processes. Additionally, this proposed coefficient was used to guide the selection of piezoelectric EH materials for the power supply of a load cell integrated in a petroleum pumping system under extreme environments.