Increasing the ferroelastic phase transition temperature of hybrid perovskites through a mixed phosphonium and ammonium cation strategy

Abstract

The introduction of phosphonium cations increases the ferroelastic phase transition temperature of [(CH3)3PCH2CH2CH3]2(n-C4H9NH3)Bi2Br9 to above room temperature.

An anomalous ferroelastic phase transition arising from an unusualcis-/anti-conformational reversal of polar organic cations

“…Such a domain revolution strongly veried the reversible and normal ferroelastic phase transition for 1, i.e., between a ferroelastic LTP and a paraelastic HTP, which is similar to the behaviors of most known ferroelastic materials. [17][18][19][20][21][22][23][24][25][26][27][28][29] In contrast, in the temperature range of 300-380 K for 2, no multi-domain structure was observed at 303 K as it was in its paraelastic phase (2_LTP). Upon further heating to 380 K (2_HTP), the theoreticallypredicted multiple domains with two anti-parallel orientation states could be clearly distinguished, which then completely disappeared aer cooling back to 300 K. Therefore, as compared to 1 and most other ferroelastic materials, 2 is a rare ferroelastic material with a ferroelastic phase at HTP rather than at LTP.…”

“…Based on the cell parameters of 1 and 2 at 314 K and 340 K deduced by extrapolating the tting lines of variabletemperature cell parameters, the total spontaneous strains were estimated as 0.059 and 0.062 for 1 and 2, respectively (for details, see ESI †). 32,42 These spontaneous strain values are of intermediate level for other hybrid ferroelastics, [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] but the value for 2 (0.062) was much larger than those observed in the documented anomalous ferroelastics with inverse symmetry breaking, such as [Zn(saloph)] 2 (m-dabco) (0.02), 36 (Me 3 NCH 2 -CH 2 OH) 4 [Ni(NCS) 6 ] (0.0073), 37 and (Et 4 N)(Me 4 N)[MnBr 4 ] (0.0043). 43,44 These results implied that the anomalous ferroelastic transition and large spontaneous strain in 2 should be strongly associated with not only the order-disorder dynamic transition of cations but also the cis-/anti-conformational variations in organic cations.…”

“…9,10 Hybrid ferroelastics, as important supplements, could be assembled in solutions under moderate conditions from diverse organic and inorganic components, hence offering an eco-friendly and feasible approach for designing ferroelastic materials. [11][12][13][14] Recent years have witnessed the emergence of numerous hybrid ferroelastics, [15][16][17][18][19][20][21][22][23][24][25][26][27] such as (Me 3 NOH) 2 [ZnCl 4 ] with a large spontaneous strain of 0.129, 28 (nortropinium) [CdCl 3 ] with the ultrahigh ferroelastic phase-transition temperatures of 463 and 495 K, 29 and the chiral (R-3-chloro-2hydroxypropyltrimethylammonium) 2 CuCl 4 with seven physical channel switches. 30 According to tests on the 94 species of ferroelastic crystals suggested by Aizu, decreasing temperatures favor a symmetry reduction, and ferroelasticity generally appears at the lowtemperature phase (LTP) during a conventional ferroelastic phase transition.…”

“…9,10 Hybrid ferroelastics, as important supplements, could be assembled in solutions under moderate conditions from diverse organic and inorganic components, hence offering an eco-friendly and feasible approach for designing ferroelastic materials. 11–14 Recent years have witnessed the emergence of numerous hybrid ferroelastics, 15–27 such as (Me 3 NOH) 2 [ZnCl 4 ] with a large spontaneous strain of 0.129, 28 (nortropinium)[CdCl 3 ] with the ultrahigh ferroelastic phase-transition temperatures of 463 and 495 K, 29 and the chiral ( R -3-chloro-2-hydroxypropyltrimethylammonium) 2 CuCl 4 with seven physical channel switches. 30…”

H/F Substitution Achieved Enantiomeric Organic Inorganic Hybrid Perovskites and Trigonal Structure [DMFP]3(CdBr3)(CdBr4)

“…While inorganic oxide perovskites have dominated the research and industrial fields since the middle of last century, organic–inorganic hybrid perovskites (OIHPs) are gaining popularity as they combine the advantages of organic and inorganic components and have demonstrated promising applications in solar cells and organic light emitting diodes . Benefited from their unique framework flexibility, OIHPs can, therefore, be adapted to a variety of structures and exhibit excellent optical, , electrical, magnetic, and other properties. − It is important to note that the incorporation of chiral cations in the A sites can endow the whole bulk OIHP crystal with chirality, which cannot be achieved in conventional inorganic oxide perovskites . These materials are chiral in nature, which affects their optical and electrical properties, including circular dichroism, ferroelectricity, circularly polarized luminescence (CPL), and spin-dependent charge transport .…”