Multistep stochastic mechanism of polarization reversal in orthorhombic ferroelectrics

A stochastic model of electric-field-driven polarization reversal in orthorhombic ferroelectrics is advanced, providing a description of their temporal electromechanical response. The theory accounts for all possible parallel and sequential switching events. Application of the model to the simultaneous measurements of polarization and strain kinetics in a lead-free orthorhombic $(\mathrm{K},\mathrm{Na})\mathrm{Nb}{\mathrm{O}}_{3}$-based ferroelectric ceramic over a wide timescale of seven orders of magnitude allowed identification of preferable polarization switching paths, fractions of individual switching processes, and their activation fields. Particularly, the analysis revealed substantial contributions of coherent non-180\ifmmode^\circ\else\textdegree\fi{} switching events, which do not cause macroscopic strain and thus mimic 180\ifmmode^\circ\else\textdegree\fi{} switching processes.