  We investigated domain kinetics by measuring the polarization switching
behaviors of polycrystalline Pb(Zr,Ti)O$_{3}$ films, which are widely used in
ferroelectric memory devices. Their switching behaviors at various electric
fields and temperatures could be explained by assuming the Lorentzian
distribution of domain switching times. We viewed the switching process under
an electric field as a motion of the ferroelectric domain through a random
medium, and we showed that the local field variation due to dipole defects at
domain pinning sites could explain the intriguing distribution.
