Motion of 180° Domain Walls in Metal Electroded Barium Titanate Crystals as a Function of Electric Field and Sample Thickness

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Abstract
The domain dynamics of polarization reversal in metal electroded BaTiO3 single crystals have not been adequately described in the literature. The present paper contains quantitative measurements of the velocity of the sidewise motion of 180° domain‐walls in BaTiO3 crystals, most of which were electroded with 200‐A thick films of Au. The wall velocity has been measured as a function of several variables including the applied electric field, the crystal thickness and the impurity content added to the crystal growth melts. The wall velocity as a function of the field E is described by v∞ exp (−δ/E) where δ and v∞ are constants over several decades of velocity. The quantities δ and v∞ are the activation field and extrapolated wall velocity for E=∞, respectively. This field dependence of the wall velocity is the same as that reported previously for liquid electroded specimens. The thickness dependence of the wall velocity, which is through δ, is very pronounced and similar to that observed in measurements of other variables under different experimental conditions. The present data are explained in terms of a surface layer estimated to be of the order of 100‐A thick. It is suggested that high fields within the surface layer may give rise to electron field emission and the electroluminescence which is observed during polarization reversal. Effects on the wall motion which persist for times of the order of minutes are ascribed to dielectric relaxation phenomena. The observed dependence of the wall motion on the impurity content of the cyrstal, and several other parameters, may result from changes in the characteristics of the surface layer.