Executive Summary : | Piezoceramics-based actuators transform electrical signals into mechanical strain, known as electrostrain, with applications in microelectromechanical systems, robotics, electronic products, transportation, and accurate optical instruments. The electric field induced strain (electrostrain) is a crucial parameter for piezoelectric actuators, with high electrostrain and low hysteresis being essential for optimal performance. The electric field induced strain in ferroelectrics is primarily due to the converse of piezoelectric effect (intrinsic) and domain switching (extrinsic). The intrinsic contribution can be enhanced by adjusting the chemical composition, while the extrinsic contribution can contribute a large nonlinear strain. However, domain switching is intrinsically irrevocable due to energetic compatibility. Doping can control the functional properties of ferroelectric materials, resulting in defect dipoles and a defect dipole moment. This internal field can help switch the domain back to its primary state after the removal of the electric field, achieving a recoverable strain with minimal remnant strain. Acceptor doping induced defect dipoles also result in pinched and double hysteresis loops, which are favorable for energy storage device applications. Pb-based piezoceramic actuators dominate the market, but due to its toxic nature, countries have imposed regulations against their use. Researchers are now working on lead-free piezoceramics, with Bi0.5Na0.5TiO3 (BNT) based relaxor systems being chosen due to their strong ferroelectricity, high Curie temperature, and potential reversible phase transition. However, BNT-based relaxor systems have large hysteresis and high remnant strain, making further research necessary to achieve a large recoverable strain with minor hysteresis. |