“…Piezoelectric materials play a vital role in various applications including sensors, actuators, resonators, and vibration energy harvesters, particularly in the rapidly developing field of micro-electromechanical systems (MEMS). − MEMS that use piezoelectric devices, also called piezoelectric MEMS, have advantages over their electrostatic and electromagnetic counterparts, such as a simple structure and small size. , To date, Pb-based piezoelectric materials, such as Pb(Zr,Ti)O 3 (PZT) and Pb(Mg 1/3 Nb 2/3 )O 3 –PbTiO 3 (PMN–PT), have been preferred because of their excellent piezoelectric properties. , However, environmental issues and stricter regulations such as the Restriction of Hazardous Substances (RoHS) directive have necessitated the development of alternative materials that do not contain toxic Pb. − In the context of next-generation smart electronics, robotics, and the Internet of Things (IoT), advances in Pb-free piezoelectric thin films are essential for addressing the requirements of high-performance, energy-efficient devices while aligning with sustainable development practices. − …”