Lead-Free Piezoelectric Transducers.

Research activities on lead-free piezoelectric materials have been ongoing for over 20 years. Generally, the applicability of the main material families is less universal than that of lead-based compositions such as lead zirconate titanate, but in some cases, the corresponding applications have already been identified. Due to the extensive research, it is now possible to manufacture demonstrators and prototypes for different applications and the authors propose in this article to take stock of these advances. For this, we have chosen to first recall briefly the main new material systems using a simplistic "soft" and "hard" classification for approaching the various resonant transducer applications. Medical imaging applications that represent one of the most important fields are presented in a second step together with other low-power transducers. Then, a variety of applications are merged under the heading of high-power transducers. In addition, we mention two points that are important to consider when manufacturing at a larger scale. For the design of transducers, complete datasets must be available, especially if modeling tools are used. Finally, the commercialization of these lead-free materials imposes essential secondary requirements in terms of availability, reproducibility, sample size, and so on.