Fluoridation Achieved Antiperovskite Molecular Ferroelectric in [(CH₃)₂(F-CH₂CH₂)NH]₃(CdCl₃)(CdCl₄)

Abstract

Antiperovskites have developed to be one kind of important functional material over the past few decades, showing abundant physical properties such as negative thermal expansion and superconductivity, etc. However, antiperovskite ferroelectrics have scarcely been discovered in inorganic ceramics. In this article, we report a new organic−inorganic hybrid antiperovskite ferroelectric [(CH 3 ) 2 (F-CH 2 CH 2 )NH] 3 (CdCl 3 )(CdCl 4 ) based on the strategy of molecular design. The replacement of one methyl in [(CH 3 ) 3 NH]CdCl 3 with ethyl produces the lower symmetric [(CH 3 ) 2 (CH 2 CH 3 )NH]CdCl 3 with nonpolar perovskite structure, while the polar hexagonal antiperovskite structure with the formula of X 3 BA (where X = [(CH 3 ) 2 (F-CH 2 CH 2 )NH] + , B = [CdCl 3 ] − , and A = [CdCl 4 ] 2− ) was received after further fluoridation of the ethyl group. Therefore, fluoridation successfully achieves the structural transformation from perovskite to antiperovskite, as well as the significant changes in physical properties from nonferroelectric to ferroelectric. The antiperovskite [(CH 3 ) 2 (F-CH 2 CH 2 )NH] 3 (CdCl 3 )(CdCl 4 ) exhibits typical ferroelectric phase transition above room temperature (T c = 333 K) including thermal anomalies, dielectric transitions, and second harmonic generation (SHG) responses. Moreover, lower coercive fields and easy polarization switching are observed by the measurements of hysteresis loops and ferroelectric domains. The saturated polarization (P s ) of 4.0 μC/cm 2 is almost 10 times as large as those recently discovered antiperovskite molecular ferroelectrics. This finding provides a novel strategy to design and explore more antiperovskite organic−inorganic hybrid ferroelectric materials.

Organic‐inorganic Hybrid ([BrCH2CH2N(CH3)3]+2[CdBr4]2−) with Unusual Ferroelectric and Switchable Dielectric Bifunctional Properties over Different Temperature Range

“…Concerning the structural properties of ferroelectric space group Pca 2 1 , the crystals of BETABCdBr should exhibit spontaneous polarization ( P s ) along the c axis in the ferroelectric phase. As illustrated in Figure , the obtained typical P ‐ E hysteresis loop show the measured P s of around 4.6 μ C/cm 2 , comparable to that of 3‐(Fluoropyrrolidinium)MnCl 3 or [(CH 3 ) 2 (F‐CH 2 CH 2 )NH] 3 (CdCl 3 )(CdCl 4 ) . Replacing Cu with larger size of Cd atom, BETABCdBr is endowed with ferroelectricity at room‐temperature phase due to good momentum matching.…”

A Three‐Dimensional M3AB‐Type Hybrid Organic–Inorganic Antiperovskite Ferroelectric: [C3H7FN]3[SnCl6]Cl

“…Theo btained saturate polarization (P s )i sa bout 0.94 mCcm À2 .T his value is larger than those of the recently discoveredo rganic-inorganic antiperovskite ferroelectrics [(CH 3 ) 3 NH] 3 (MnCl 4 )(MnCl 3 )( 0.4 mCcm À2 ) [7a] and [(CH 3 ) 3 NH] 3 (MnBr 4 )(MnBr 3 )( 0.45 mCcm À2 ), [7b] but smaller than that of the organic-inorganic antiperovskite ferroelectric [(CH 3 ) 2 (F-CH 2 CH 2 )NH] 3 (CdCl 4 )(CdCl 3 )( 4.0 mCcm À2 ). [9]…”

“…[8] Very recently,b yt he molecular design method of H/F substitution on the [(CH 3 ) 2 (CH 2 CH 3 )NH] + ion, we successfully regulated the non-ferroelectric perovskite [(CH 3 ) 2 (CH 2 CH 3 )NH]CdCl 3 to the ferroelectric antiperovskite [(CH 3 ) 2 (F-CH 2 CH 2 )NH] 3 (CdCl 4 )(CdCl 3 ). [9] The emergenceo ft his organic-inorganic hybrid antiperovskite structure opens up a vast fieldf or the antiperovskite family. Inspired by this, it can be assumedt hat an egative divalent anion Ac an be an acid anion or az ero-dimensional metal halide anion, such as SO 4 2À , MX 4 2À (M = Cd 2 + ,M n 2 + ,Z n 2 + ,C u 2 + ,e tc.,X = Cl À ,B r À ,I À ), or SnX 6 2À ,a nd the negative monovalenta nion Bc an also be a halide anion,a cid anion, or one-dimensional metal halide chains, such as Cl À ,C lO 4 À ,( CdCl 3 ) n À .I nt his way,s ome unique antiperovskites can be assembled according to the desired physicalproperties.…”

Designing and Constructing a High‐Temperature Molecular Ferroelectric by Anion and Cation Replacement in a Simple Crown Ether Clathrate

“…[14][15][16][17][18][19][20][21][22][23][24][25][26] How to precisely design and construct new family molecular ferroelectrics through the regulation of an existing molecule system is ag reat challenge. [1,7,[27][28][29] As is known, to be a ferroelectric it must satisfy some basic conditions, i) undergoes as olid reversible phase transition, ii)the ferroelectric should crystallize in the ten polar point groups1 ,m,2 ,mm2, 3, 3m, 4, 4mm, 6, 6mm, iii)exists as pontaneousp olarization which can be changed by the electric field. [30] In general, al ot of molecular compounds usually undergo reversible phase transitions;h owever,t hey can't be ferroelectrics because they have high structural symmetry and cannot produce the polarization.…”

“…[30] In general, al ot of molecular compounds usually undergo reversible phase transitions;h owever,t hey can't be ferroelectrics because they have high structural symmetry and cannot produce the polarization. [12,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] Therefore, our strategy is to keep the body structure of this non-ferroelectric phase transition molecular system with tiny local modifications, such molecular tailoring operation may retain the "driving force" of the body structure but reducei ts symmetry to introduce ad ipole moment into such molecular system, and then potentially construct novel ferroelectrics from such non-ferroelectricm olecular compound. In this way,X iong.…”