Quasi-one-dimensional domain walls in ferroelectric ceramics: Evidence from domain dynamics and wall roughness measurements

Direct measurements of the motion of domain walls in disordered ferroelectrics provide important information on their interaction with defects, which is crucial for the functioning of various ferroelectric devices such as high-K capacitors and ferroelectric-based memories. In this work, we report on the results of the nanoscale measurements of domain-wall velocity and static domain-wall roughness in disordered (Pb,La)(Zr,Ti)O₃ (PLZT) ceramics prepared by hot press sintering. Relaxation of domain walls to their equilibrium configurations at short length scales yields the apparent roughness exponent χ ≈ 0.67 in PLZT 9.5/65/35. At the same time, the dynamical exponent was found to be about 0.25 from the independent measurements of domain-wall creep under local application of electric field. An analysis of these two values points to the effective dimensionality d_eff = 1 for the domain walls in PLZT with high La content. This result is confirmed by the layer-by-layer polishing followed by the imaging of an artificially created domain. The origin of disorder and its dependence on La concentration in PLZT solid solutions are discussed.