An ideal amplitude window against electric fatigue in BaTiO₃-based lead-free piezoelectric materials

Electric fatigue has been a vexing issue for Pb(Zr,Ti)O₃ ceramics, the material-of-choice for piezoelectric technologies, where higher field amplitudes always lead to a more severe property degradation. Thus, piezoelectric devices must be driven under low electric fields to ensure performance reliability, which results in a low efficiency. In the past decade, the intensive worldwide research on lead-free compositions has identified a few ceramics with piezoelectric properties comparable to those of lead-containing ones. However, their resistance to electric fatigue has not been well studied. In this work, we report an abnormal amplitude dependence of electric fatigue in lead-free piezoelectrics: A BaTiO₃-based ceramic suffers fatigue degradation when the field amplitude is low, but exhibits an amplitude window at higher fields with essentially no fatigue. Furthermore, electric-field in-situ transmission electron microscopy (TEM) experiments up to 10⁵ cycles are conducted to clearly reveal that the degradation at low fields is due to the unique single-domain state. We, therefore, have identified an ideal amplitude window with performance at full potential and, at the same time, extremely high reliability for a lead-free piezoelectric ceramic that is promising to replace Pb(Zr,Ti)O₃.