Crack tip 90° domain switching in tetragonal lanthanum-modified lead zirconate titanate under an electric field

Lanthanum-modified lead zirconate titanate ferroelectric ceramics (Pb_0.96La_0.04)(Zr_0.40Ti_0.60)_0.99O₃ were synthesized by the conventional powder processing technique. X-ray diffraction experiments revealed that the samples belong to the tetragonal phase with a = b = 0.4055 nm, c = 0.4109 nm, and c/a = 1.013. After being poled, the samples were indented with a 5-kg Vickers indenter, and lateral electric fields of 0.4 E_c, 0.5 E_c, and 0.6 E_c (E_c = 1100 V/mm) were applied, respectively. Field-emission scanning electron microscopy showed that 90° domain switching appeared near the tip of the indentation crack under a lateral electric field of 0.6 E_c. A mechanism of 90° domain switching near the crack tip under an electric field is discussed.