A New Material for High‐Temperature Lead‐Free Actuators

Abstract

Abstract Unimorph cantilevers are made from 0.5BaTiO 3 ‐0.5Sm 2 O 3 (BTO‐SmO) self‐assembled vertical heteroepitaxial nanocomposite thin films, grown by PLD on (001) SrTiO 3 single crystal substrates. The films remain piezoelectric up to at least 250 °C without losing any actuation. The longitudinal piezoelectric coefficient, d 33 , is ≈45 to 50 pm V −1 measured from room temperature to 250 °C. The transverse piezoelectric coefficient, d 31 , a key parameter of actuator performance, exceeds PZT (Pb 1–x Zr x TiO 3 ) films at >200 pm V −1 . Since the d 31 coefficient was found to be positive, this opens up exciting new applications opportunities. The possible reasons for d 31 > 0 are discussed in the light of 3D strain control in the nanocomposites.