Strong Improper Ferroelasticity and Weak Canted Ferroelectricity in a Martensitic‐Like Phase Transition of Diisobutylammonium Bromide

Abstract

Diisobutylammonium bromide is found to be a unique improper ferroelastic in which the elastic degrees of freedom seem to play the essential role, giving rise to a domain pattern resembling that of martensitic phase transitions. A weak canted ferroelectricity turns out switchable by an electric field.

Tuning Order‐Disorder Phase Transition through Regulating the Substituent Group of Anion

“…There is a thermal hysteresis of 2 K between two reversible peaks, which suggests that 1 undergoes a first-order and reversible phase transition. [2,[13][14][15] Based on the DSC curves of 1, the average enthalpy change ∆H is estimated to be 7169.2 J•mol 1 . According to the entropy change ∆S＝∆H/T c , ∆S is obtained as 25.88…”

“…As shown in Figure 1b, an endothermic peak and an exothermic peak appear at 251 and 249 K, respectively. There is also a thermal hysteresis of about 2 K, and such a thermal hysteresis will enlarge when the heating and cooling rate increases ( Figure S3), indicating that 2 undergoes a first-order phase transition at 251 K. [2,[13][14][15] At around 282 K, another pair of sharp peaks appears, which is a feature of phase transition. [23] Since the phase transitions at 290 and 282 K occur close to each other, it is difficult to analyze the structural phase between them.…”

“…[10] Based on this, achieving modulating the phase transition involves in engineering the reorientational order-disorder motion of the moiety unit. Even a large number of order-disorder phase transition materials have been explored, [8,[10][11][12][13][14][15][16][17][18][19] however, those processes in a large part are left to chance and not easily controllable. [20] Therefore, studying the details of the relationship between the structure and the phase transition process is the key step to further control and design the target phase transition materials.…”

Enormous lattice distortion through an isomorphous phase transition in an organic–inorganic hybrid based on haloantimonate(iii)

“…Change in the dynamics/reorientation of such a dipolar units in the crystal lattice may lead to interesting dielectric properties (tunable and switchable dielectric constant) and PTs. 29 Here we present two novel organic-inorganic hybrid materials, diisobutylammonium analogs based on the haloantimonates(III);…”

Phase sequence in diisopropylammonium iodide: avoided ferroelectricity by the appearance of a reconstructed phase

“…[4][5][6] However, in recent years there has been a significant breakthrough in small-molecular-weight organic single-or two-component polar materials which are characterized by excellent physical properties such as an extremely high value of the spontaneous polarization, a high Curie temperature, good thermal stability, mechanical flexibility, optical transparency and lightweight. [7][8][9][10][11][12][13][14][15][16][17] The new materials are also environment-friendly, easy to prepare, relatively non-expensive and non-toxic. The most spectacular example is the wellknown croconic acid which belongs to the group of singlecomponent hydrogen-bonded ferroelectrics and possesses as high a spontaneous polarization as about 21 μC cm −2 .…”