Plastic/Ferroelectric Crystals with Easily Switchable Polarization: Low-Voltage Operation, Unprecedentedly High Pyroelectric Performance, and Large Piezoelectric Effect in Polycrystalline Forms

Molecular ferroelectric
crystals have attracted growing interest
as potential alternatives to conventional lead-based ceramic ferroelectrics.
We have recently discovered that a class of compounds known as plastic
crystals can show multiaxial ferroelectricity, which allows ferroelectric
performance even in polycrystalline forms. Here, we report new plastic/ferroelectric
ionic molecular crystals that exhibit remarkably small coercive electric
fields at room temperature. The easily switchable ferroelectric polarization
enables low-voltage switching operations and high-frequency performance.
Such ferroelectric crystals can be readily processed into bulk polycrystalline
forms with desired shapes that are characterized by unprecedentedly
high pyroelectric figures of merit and large piezoelectricity. These
multifunctional molecular crystals represent highly attractive prospects
for device elements with a diverse range of applications, which will
significantly boost the development of molecular ferroelectric crystals.