  The polar states of uniaxial ferroelectric nanoparticles interacting with a
surface system of electronic and ionic charges with a broad distribution of
mobilities is explored, which corresponds to the experimental case of
nanoparticles in solution or ambient conditions. The nonlinear interactions
between the ferroelectric dipoles and surface charges with slow relaxation
dynamics in an external field lead to the emergence of a broad range of
paraelectric-like, antiferroelectric-like ionic, and ferroelectric-like
ferroionic states. The crossover between these states can be controlled not
only by the static characteristics of the surface charges, but also by their
relaxation dynamics in the applied field. Obtained results are not only
promising for advanced applications of ferroelectric nanoparticles in
nanoelectronics and optoelectronics, they also offer strategies for
experimental verification.
