Velocity of Sidewise 180° Domain-Wall Motion in BaTiO3as a Function of the Applied Electric Field

New techniques are described which permit one to reverse the direction of the spontaneous polarization in liquid-electroded single crystals of BaTi${\mathrm{O}}_3$ with one growing domain which nucleates at a predetermined location on the crystal and then expands through sidewise 180° domain-wall motion until the spontaneous polarization in the entire electroded area is reversed. Measurements of the rate of growth of the single domain for a range of applied electric fields give rise to the first quantitative data on the field dependence of the sidewise 180° domain-wall velocity in BaTi${\mathrm{O}}_3$. It is found that this wall velocity is given by $v=v_{\infty }{e}^{-\frac{\delta }{E}}$, where $\delta$ is several thousand volts per centimeter and $v_{\infty }$ is in general of the order of 10 cm ${\sec }^{-1\mathrm{}}$. The fields employed in these measurements were in the neighborhood of several hundred volts per centimeter and the wall velocities varied from about ${10}^{-6\mathrm{}}$ cm ${\sec }^{-1\mathrm{}}$ to ${10}^{-2\mathrm{}}$ cm ${\sec }^{-1\mathrm{}}$. The measured field dependence of the wall velocity is indicative of a nucleation mechanism for the wall motion, and it is shown that the equation of motion usually employed for domain boundaries does not describe the sidewise 180° wall motion in BaTi${\mathrm{O}}_3$. In addition, the well-known $e^{-\frac{\alpha }{E}}$ polarization reversal characteristics of metal-electroded crystals are shown to be consistent with wall motion of the type found in this research.