- Large Piezoelectric Effect in a Lead-Free Molecular Ferroelectric Thin Film
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Piezoelectric materials have been widely used in various applications, such as high-voltage sources, actuators, sensors, motors, frequency standard, vibration reducer, and so on. In the past decades, lead zirconate titanate (PZT) binary ferroelectric ceramics have dominated the commercial piezoelectric market due to their excellent properties near the morphotropic phase boundary (MPB), although they contain more than 60% toxic lead element. Here, we report a lead-free and one-composition molecular ferroelectric trimethylbromomethylammonium tribromomanganese(II) (TMBM-MnBr3) with a large piezoelectric coefficient d33 of 112 pC/N along polar axis, comparable with those of typically one-composition piezoceramics such as BaTiO3 along polar axis [001] (~90 pC/N) and much greater than those of most known molecular ferroelectrics (almost below 40 pC/N). More significantly, the effective local piezoelectric coefficient of TMBM-MnBr3 films is comparable to that of its bulk crystals. In terms of ferroelectric performance, it is the low coercive voltages, combined with the multiaxial characteristic, that ensure the feasibility of piezo film applications. Based on these, along with the common superiorities of molecular ferroelectrics like light weight, flexibility, low acoustical impedance, easy and environmentally friendly processing, it will open a new avenue for the exploration of next-generation piezoelectric devices in industrial and medical applications.
- Liao, Wei-Qiang,Tang, Yuan-Yuan,Li, Peng-Fei,You, Yu-Meng,Xiong, Ren-Gen
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- Competitive Halogen Bond in the Molecular Ferroelectric with Large Piezoelectric Response
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Molecular piezoelectrics are attracting tremendous interest because of their easy processing, light weight, low acoustical impedance, and mechanical flexibility. However, reports of molecular piezoelectrics with a piezoelectric coefficient d33 comparable to piezoceramics such as barium titanate (BTO, 90-190 pC/N) have been scarce. Here, we present a uniaxial molecular ferroelectric, trimethylchloromethylammonium tribromocadmium(II) (TMCM-CdBr3), in which the halogen bonding might be a possible critical point for the stabilization of one-dimensional (1D) {CdBr3}- chain and further reservation of its ferroelectricity in such organic-inorganic hybrid crystalline systems. It has a large d33 of 139 pC/N, 1 order of magnitude higher than those of most classically uniaxial ferroelectrics such as LiNbO3 (6-16 pC/N) and Rochelle salt (~7 pC/N), and comparable with those of multiaxial ferroelectrics such as BTO and trimethylbromomethylammonium tribromomanganese(II) (112 pC/N). Moreover, the simple single-crystal growth and easy-to-find polar axis enable it to hold a great potential for applying in the single-crystal form. In light of the strong, specific, and directional halogen-bonding interactions, this work provides possibilities to explore new classes of molecular piezoelectrics and contribute to further developments.
- Liao, Wei-Qiang,Tang, Yuan-Yuan,Li, Peng-Fei,You, Yu-Meng,Xiong, Ren-Gen
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- Target Designing Phase Transition Materials through Halogen Substitution
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Crystalline materials have received extensive attention due to their extraordinary physical and chemical properties. Among them, phase transition materials have attracted great attention in the fields of photovoltaic, switchable dielectric devices, and ferroelectric memories, etc. However, many of them suffer from low phase transition temperatures, which limits their practical application. In this work, we systematically designed crystalline materials, (TMXM)2PtCl6 (X=F, Cl, Br, I) through halogen substitution on the cations, aiming to improving phase transition temperature. The resulting phase transition of (TMXM)2PtCl6 (X=F, Cl, Br, I) get a significant enhancement, compared to the parent compound [(CH3)4N]2PtCl6 ((TM)2PtCl6). Such phase transition temperature enhancement can be attributed to the introduction of halogen atoms that increase the potential energy barrier of the cation rotation. In addition, (TMBM)2PtCl6 and (TMIM)2PtCl6 have a low symmetry and crystallize in the space group C2/c and P212121, respectively. This work highlights the halogen substitution in designing crystal materials with high phase transition temperature.
- Cheng, Hao,Yang, Meng-Juan,Xu, Yu-Qiu,Li, Meng-Zhen,Ai, Yong
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p. 752 - 756
(2021/03/17)
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- Precise Molecular Design Toward Organic-Inorganic Zinc Chloride ABX3 Ferroelectrics
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Organic-inorganic ABX3 (A, B = cations, X = anion) hybrids with perovskite structure have recently attracted tremendous interest due to their structural tunability and rich functional properties, such as ferroelectricity. However, ABX3 hybrid ferroelectrics with other structures have rarely been reported. Here, we successfully designed an ABX3 hybrid ferroelectric [(CH3)3NCH2F]ZnCl3 with a spontaneous polarization of 4.8 μC/cm2 by the molecular modification of [(CH3)4N]ZnCl3 through hydrogen/halogen substitution. It is the first zinc halide ABX3 ferroelectric, which contains one-dimensional [ZnCl3]-n chains of corner-sharing ZnCl4 tetrahedra, distinct from the anionic framework of corner-sharing or face-sharing BX6 octahedra in the ABX3 perovskites. From zero dimension to one dimension, the high symmetry of ZnCl4 tetrahedra is broken, and all of them align along one direction to form a polar [ZnCl3]-n chain, beneficial to the generation of ferroelectricity. This finding provides an efficient polar anionic framework for enriching the family of hybrid ferroelectrics by assembling with various cations and should inspire further exploration of new classes of organic-inorganic ABX3 ferroelectrics.
- Chen, Lizhuang,Liao, Wei-Qiang,Ai, Yong,Li, Junyi,Deng, Siyu,Hou, Yunlong,Tang, Yuan-Yuan
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supporting information
p. 6236 - 6243
(2020/04/27)
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- High-temperature reversible phase transitions and exceptional dielectric anomalies in cobalt(ii) based ionic crystals: [Me3NCH2X]2[CoX4] (X = Cl and Br)
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Two isostructural ionic cobalt(ii) halides, trimethylchloromethyl ammonium tetrachlorocobalt(ii) (1, [Me3NCH2Cl]2[CoCl4]) and trimethylbromomethyl ammonium tetrabromocobalt(ii) (2, [Me3NCH2Br]2[CoBr4]), have been discovered as new high-temperature phase transition materials. 1 exhibits two successive structural phase transitions from P212121 to P21/c at 252 K and then to Pnma at 335 K, accompanied by step-like dielectric anomalies. The two-step sequential reversible phase transitions of 1 derive from the order-disorder transformation of CoCl4 anions and organic Me3NCH2Cl cations, respectively. Its analogue 2 also crystallizes in P21/c at 293 K by changing the halogen atoms of both cations and anions of 1. Unlike 1, 2 displays only one structural phase transition with a much higher transition temperature at 387 K, which is mainly influenced by intermolecular interactions and more energy is required to provide the freedom of the motion. All the findings in the present work indicate that the phase transition temperature and properties of materials can be tuned by using halogens in this series of compounds, which could open a new way to design and assemble novel high-temperature phase transition materials.
- Hua, Xiu-Ni,Huang, Chao-Ran,Gao, Ji-Xing,Lu, Yang,Chen, Xiao-Gang,Liao, Wei-Qiang
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p. 6218 - 6224
(2018/05/07)
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- A high-temperature molecular ferroelastic phase transition and switchable dielectric response in the trimethylbromomethylammonium salt [C4H11NBr] [PF6]
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By introducing halogens to 16 symmetric tetramethylammonium, one new molecular ferroelastic compound [TMBMA] [PF6] (1) (TMBMA = trimethylbromomethylammonium) was successfully synthesized. Differential scanning calorimetry (DSC) measurements demonstrated that 1 underwent a typical first-order phase transition at ca. 380 K with a large thermal hysteresis of 30 K. Single crystal X-ray diffraction data, the variable-temperature powder X-ray diffraction (PXRD) patterns and the complex domain-wall orientations suggested that the phase transition from monoclinic (P21/c) to cubic (Pm3m) belongs to a ferroelastic phase transition with an Aizu notation of m3mF2/m. Dielectric studies show that 1 exhibits distinct switchable dielectric behavior and satisfactory thermal stability, revealing its potential application in dielectric switches. As expected, the TMBMA cations bearing an ordered-disordered motion turn out to be crucial in the generation of the ferroelastic phase transition. Therefore, this molecular design strategy of introducing halogens to tetraalkylammoniums can not only reduce the symmetry of the tetraalkylammonium molecules at room temperature, but can also maintain the highly disordered characteristics at high temperatures. This provides an efficient route for us to find new molecular ferroelastics and dielectric switches.
- Chen, Xiao-Gang,Gao, Ji-Xing,Hua, Xiu-Ni,Liao, Wei-Qiang
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p. 14909 - 14913
(2018/10/02)
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- High-temperature sequential structural transitions with distinct switchable dielectric behaviors in two organic ionic plastic crystals: [C4H11NBr] [ClO4] and [C4H11NBr] [BF4]
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Two new organic ionic plastic crystals (OIPCs), [TMBM] [ClO4] (1) and [TMBM] [BF4] (2) (TMBM = trimethylbromomethyl ammonium), were successfully synthesized. Systematic characterization via differential scanning calorimetry (DSC), va
- Lu, Si-Qi,Chen, Xiao-Gang,Gao, Ji-Xing,Lu, Yang,Hua, Xiu-Ni,Liao, Wei-Qiang
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p. 454 - 459
(2018/02/07)
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- Kinetic evidence for a novel, Grob-like substitution/fragmentation mechanism for the reaction of nucleophiles with trialkylammoniomethyl halides
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Kinetic evidence is presented in favor of a concerted, bimolecular mechanism for the unusual nucleophilic substitution/fragmentation reactions of iodide ion with (halomethyl)trimethylammonium salts. The relative reactivities of allyl, ethyl and methyl groups for this Grob-like reaction are also determined. Activation parameters are presented for the thermal reactions of 1-iodo-N,N,N-trimethylmethaniminium iodide (log A = 8.7. Ea = 19.0 kcal mol-1) and 1-iodo-N-allyl-N,N-dimethylmethaniminium iodide (log A = 14.6, Ea = 25.7 kcal mol-1) in acetonitrile, the latter reaction having an observed second order rate constant 39 times larger than the former at 70 °C. The results are compared with the classic data of Hughes, Ingold and Conant for SN2 reactions of alkyl halides.
- Fletcher, Michelle O.,Zhang, Li,Vu, Quyen,Dolbier Jr., William R.
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p. 1187 - 1192
(2007/10/03)
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- The Quarternisation of Tertiary Amines with Dihalomethane
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Whereas dichloromethane is inert towards reaction with most tertiary amines under atmospheric conditions, it readily reacts with a wide variety at high pressures to produce α-chloro quaternary ammonium and even bis-ammonium salts.The reaction of dichloromethane and dibromomethane with eleven tertiary amines and properties of the products are described.
- Almarzoqi, B.,George, A. V.,Isaacs, N. S.
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p. 601 - 608
(2007/10/02)
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