High voltage coefficient piezoelectric materials and their applications

The piezoelectric dij coefficient is often regarded in materials science as the most important figure of merit of piezoelectric performance. For many applications, the piezoelectric gij coefficient which correlates to voltage output and sensitivity of a piezoelectric material can be considered of equal or increased importance, however is often an overlooked parameter in materials science literature. The aim of this review is to highlight the importance of this parameter and to provide insight into the mechanisms that drive a high piezoelectric voltage coefficient in single crystal, polycrystalline, and composite form. For bulk ceramics, special attention is given to tetragonal systems due to the availability of electrical and crystallographic data allowing for a clear structure-property relation. Orthorhombic and rhombohedral systems are mentioned and specific cases highlighted, however investigating structure-property relations is difficult due to the lack of crystallographic datasets. Composite materials have been the forefront of high gij piezoelectric materials over the decades and are therefore also considered in both ceramic-matrix and polymer-matrix form. An overview of applications in medical, energy, fishing and defence industries where a high gij is desirable are considered and the scientific and commercial considerations that must be made for the transition from laboratory to industry are discussed from the perspective of integrating new piezoelectric materials into sonar devices.