Reversible electric field induced nonferroelectric to ferroelectric phase transition in single crystal nanorods of potassium nitrate

Single-crystal rods of the α-phase of potassium nitrate were grown with [010] uniform crystallographic orientation inside a matrix of aluminum oxide nanopores. The pores were prepared by anodization of polished aluminum substrates. The potassium nitrate single crystals were grown inside the pores from a supersaturated aqueous solution at various temperatures. Dielectric polarization measurements of the porous film filled with the potassium nitrate crystals show an electric field induced reversible transition from the nonferroelectric α-phase to the ferroelectric γ-phase at about 200kV∕cm. The ferroelectric γ-phase has a coercive field of about 169kV∕cm and remnant polarization of about 0.216μC∕cm2.