Large electromechanical strain and unconventional domain switching near phase convergence in a Pb-free ferroelectric
Résumé
In many ferroelectrics, large electromechanical strains are observed near regions of composition-or temperature-driven phase coexistence. Phenomenologically, this is attributed to easy reorientation of the polarization vector and/or phase transition, although their effects are highly convoluted and difficult to distinguish experimentally. Here, we used synchrotron X-ray scattering and digital image correlation to differentiate between the microscopic mechanisms leading to large electrostrains in an exemplary Pb-free piezoceramic Sn-doped barium calcium zirconate titanate. Large electrostrains of~0.2% measured at roomtemperature are attributed to an unconventional effect, wherein polarization switching is aided by a reversible phase transition near the tetragonal-orthorhombic phase boundary. Additionally, electrostrains of~0.1% or more could be maintained from room temperature to 140°C due to a succession of different microscopic mechanisms. In situ X-ray diffraction elucidates that while 90°domain reorientation is pertinent below the Curie temperature (T C), isotropic distortion of polar clusters is the dominant mechanism above T C .
Domaines
Physique [physics]
Origine : Publication financée par une institution