In Situ Transmission Electron Microscopy of Electric Field‐Triggered Reversible Domain Formation in Bi‐Based Lead‐Free Piezoceramics

A lead‐free piezoelectric 0.91(Bi 1/2 Na 1/2 )TiO 3 –0.06BaTiO 3 –0.03(K 0.5 Na 0.5 )NbO 3 ceramic with high strain was examined in situ under an applied electric field using the transmission electron microscope. No domain structure is observed without an electric field, but an alternating electric field leads to the reversible formation of a lamellar domain structure. Correlations to polarization and strain hysteresis loop measurements indicate an electric field‐induced phase transition from a nonpolar to a ferroelectric state and vice versa.