New ferroelastic properties and the paraelectric-ferroelectric-paraelectric phase transitions of Rochelle salt

Abstract

The NMR spectra and the spin-lattice relaxation times, T1, of Rochelle salt crystals were studied as functions of temperature. Two groups of resonance lines were found in the 23Na and 39K NMR spectra of the paraelectric phases below TC1 and above TC2, whereas four groups of resonance lines were obtained in the 23Na and 39K NMR spectra of the ferroelectric phase between TC1 and TC2. To investigate the extra two groups of resonance lines in the ferroelectric phase, the stress-strain hysteresis loop of the Rochelle salt crystal was obtained, and the ferroelastic character of the Rochelle salt crystals suggested by Sapriel’s theory was established by the relationship between the 23Na and 39K NMR spectra and the stress-strain hysteresis loop results. Therefore, ferroelastic and ferroelectric properties coexist in the phase between TC1 and TC2.

A Molecular Crystal Shows Multiple Correlated Magnetic and Ferroelectric Switchings

“…Notably, although paraelectric-ferroelectric-paraelectric phase transitions have been observed for several molecular ferroelectrics, the distinct structural explanation offered here is novel. [51][52][53] The ferroelectric structural changes of the single crystal are associated with slight variations in the coordination configuration of the Co(II) complex cations through hydrogen-bond interactions. To gain further insight into the influence of these minute structural variations on the magnetic properties of the crystal, we performed the state-of-the-art ab initio calculations using the CASSCF/NEVPT2 approach.…”

Room temperature ferroelectric effect and enhanced dielectric permittivity in Rochelle salt/PVA percolative composite films

“…Very recently low loss high dielectric permittivity in KDP/PVA percolative composite has reported by Uddin et al [15] but such composite is not applicable in the fabrication of memory devices due to lack of ferroelectric behavior at ambient temperature. The NMR spectra and spin-lattice relaxation times, T 1 , of Rochelle salt crystals as functions of temperature were studied by Lim and Lee [16], exhibited that the Rochelle salt is multiferroic (ferroelectriceferroelastic) between T C1 (w255 K) and T C2 (w297 K) but the room temperature ferroelectric and dielectric properties in Rochelle salt/PVA composite films have not yet been reported. Thus to develop a composite material with high dielectric permittivity, low dielectric loss and improved ferroelectric property with lower filler concentration at room temperature is too challenging.…”

Tunable Thermal Conductivity of Ferroelectric P(VDF-TrFE) Nanofibers via Molecular Bond Modulation

“…Ferroelectrics usually have piezoelectric properties that generated tremendous interests in electrical field applications including energy storage, actuators, and sensors. [6][7][8][9] Rochelle salts [10] was discovered in the last century, whose polarization undergoes a hysteresis loop with electric field, [11][12][13] similar to the magnetic hysteresis loop in ferromagnetic materials. [14,15] Rochelle salts founded a new stage among numerous ferroelectric researches and also developed the field which has been dominated by inorganic ferroelectrics such as Pb(Zr𝑥Ti1−𝑥)O3 (PZT) [16,17] and BaTiO3.…”