Record Enhancement of Curie Temperature in Host-Guest Inclusion Ferroelectrics

Solid-state molecular rotor-type materials such as host-guest inclusion compounds are very desirable for the construction of molecular ferroelectrics. However, they usually have a low Curie temperature (T-c) and uniaxial nature, severely hindering their practical applications. Herein, by regulating the anion to control momentum matching in the crystal structure, we successfully designed a high-temperature multiaxial host-guest inclusion ferroelectric [(MeO-C6H4-NH3)(18-crown-6)][TFSA] (MeO-C6H4-NH3 = 4-methoxyanilinium, TFSA = bis(trifluoromethanesulfonyl)ammonium) with the Aizu notation of mmmFm. Compared to the parent uniaxial ferroelectric [(MeO-C6H4-NH3)(18-crown-6)][BF4] with a T-c of 127 K, the introduction of larger TFSA anions brings a lower crystal symmetry at room temperature and a higher energy barrier of molecular motions in phase transition, giving [(MeO-C6H4-NH3)(18-crown-6)][TFSA] multiaxial ferroelectricity and a high T-c up to 415 K (above that of BaTiO3). To our knowledge, such a record temperature enhancement of 288 K makes its T-c the highest among the reported crown-ether-based ferroelectrics, giving a wide working temperature range for applications in data storage, temperature sensing, actuation, and so on. This work will provide guidance and inspiration for designing high-T-c host-guest inclusion ferroelectrics.

Automated summary

By controlling momentum matching in the crystal structure, a high-temperature multiaxial host-guest inclusion ferroelectric was successfully designed, with a T-c of 415 K. Compared to the parent uniaxial ferroelectric with a T-c of 127 K, this design achieved a record temperature enhancement of 288 K, providing a wide working temperature range for applications.