Molecular Ferroelectric with Most Equivalent Polarization Directions Induced by the Plastic Phase Transition

Besides the single crystals, ferroelectric
materials are actually
widely used in the forms of the polycrystals like ceramics. Multiaxial
ferroelectrics with multiple equivalent polarization directions are
preferable for such applications, because more equivalent ferroelectric
axes allow random spontaneous polarization vectors to be oriented
along the electric field to achieve a larger polarization after poling.
Most of ceramic ferroelectrics like BaTiO3 have equivalent
ferroelectric axes no more than three. We herein describe a molecular-ionic
ferroelectric with 12 equivalent ferroelectric axes: tetraethylammonium
perchlorate, whose number of axes is the most in the known ferroelectrics.
Appearance of so many equivalent ferroelectric axes benefits from
the plastic phase transition, because the plastic phase usually crystallizes
in a highly symmetric cubic system. A perfect macroscopic ferroelectricity
can be obtained on the polycrystalline film of this material. This
finding opened an avenue constructing multiaxial ferroelectrics for
applications as polycrystalline materials.