(H₂dabco)[Na(BF₄)₃]: an ABX₃-type inorganic–organic hybrid perovskite compound exhibiting dielectric switching above room-temperature

Abstract

The (H2dabco)[Na(BF4)3] undergoes a static-to-dynamic phase transition at 403/386 K. Crystal structure analysis reveals that H2dabco2+ and/or BF4− undergo disordering.

Multifunctional High-Temperature Phase-Transition Energy Storage Material with Coexistence of Electrical–Thermal Double Switches:[(C6H15BrNO)2MBr4] (M = Cd and Zn)

“…Similarly, in the temperature range of 300–400 K, the diffraction peak shape of compound 2 is basically the same. However, when the temperature is 420 K (above T c ), the diffraction peak disappears partially, which proves that there is indeed a structural phase-transition phenomenon. , It is generally believed that the decrease of the diffraction peak of HTP is due to the disorder of the molecular structure, which increases the symmetry of the structure, that is, the disorder of organic cations in compounds 1 and 2 …”

“…To further confirm the existence of the structural phase transition, we measured the dielectric properties of compounds 1 and 2 because the phase transition is always accompanied by obvious dielectric anomalies. − When a static–dynamic transition occurs in the crystal structure, it causes a sudden change in the dielectric constant. , We verified the dielectric properties with the powders of compounds 1 and 2 . As shown in Figure a,b, there are obvious steplike dielectric anomalies during heating and cooling.…”

Room-temperature ferroelectric and ferroelastic orders coexisting in a new tetrafluoroborate-based perovskite

“…Since the first tetrafluoroborate-based perovskite, (H 2 dabco)(NH 4 )(BF 4 ) 3 (H 2 dabco 2+ = 1,4-diazabicyclo[2.2.2]octane-1,4-diium), was reported by Liu et al in 2011, 33 the efforts to date have added five instances. [34][35][36][37] In detail, replacing the NH 4 + cation with alkali ions yielded three analogues, (H 2 dabco)[M'(BF 4 ) 3 ] (M' = Na + , K + , Rb + ), which undergo reversible phase transitions at 403, 410, and 333 K, respectively, accompanied by step-like dielectric switches 34,36,37 and considerable latent heats for potential heat storage. Recently, changing the A-site cations yielded two analogues, (H 2 pz)[Na(BF 4 ) 3 ] (H 2 pz 2+ = piperazine-1,4-diium) 34 and (H 2 mdabco)(NH 4 )(BF 4 ) 3 (H 2 mdabco 2+ = 1-methyl-1,4diazabicyclo-[2.2.2]octane-1,4-diium), 35 which were found undergoing phase transitions at 405 K and 368 K, respectively.…”

Three-Dimensional Metal-Free Molecular Perovskite with a Thermally Induced Switchable Dielectric Response

“…Accordingly, it could be considered to consist of spherical cations discarding their chemical sense. For those organic groups with spherical geometry such as adamantine, tetra­methyl­ammonium, etc., the dynamic disorder of molecules in crystals has a common phenomenon. ,, In this case, the spherical cations (H 2 dabco 2+ ), as active components, play a key role in this phase transition from an aspherical to a quasi-spherical structure.…”