Switching kinetics of 180° domains in congruent LiNbO₃ and LiTaO₃ crystals

We present a systematic study of the switching and stabilization times of 180° domains in congruent z-cut LiNbO₃ and LiTaO₃ crystals. The domains were reversed by the application of an electric field, and the kinetics studied for the first reversal of a virgin crystal (denoted as forward poling, or, f) and the second reversal back to its original state (denoted as reverse poling, or, r) at room temperature. The switching time, t shows an exponential behavior with field as t = t₀exp[δ/(E ± E-_int)], where the - sign in the exponential is for forward poling, and + sign for reverse poling. The internal field, E-_int, parallel to the ferroelectric polarization in a virgin crystal, was measured as 41.2 kV/cm for LiTaO₃ and 22.2 kV/cm for LiNbO₃. We also showed that there exists a minimum pulse width of the applied field below which the 180° domains created by the field are unstable and show reversible wall motion. This stabilization time was measured as 1.4-2 s for LiTaO₃ and only 10-30 ms for LiNbO₃ in forward poling geometry. We present evidence that the internal field and the domain stabilization mechanisms are correlated.