A multiaxial electrical switching in a one-dimensional organic–inorganic (pyrrolidinium)2Cd2I6ferroelectric and photoluminescent crystal
Ferroelectric materials exhibiting more than one polar phase are very attractive in terms of application. The advantage of such materials is temperature-dependent switching between two different ferroelectric states. Here we report on the discovery of a unique, continuous ferroelectric – ferroelectric transformation in (C4H10N)2[Cd2I6], PCdI at 220 K. Thermal measurements suggest that phase transition is close to the continuous one. Both phases belong to the same polar monoclinic Cc space group. Temperature-variable X-ray diffraction measurements of single crystals confirm the polar nature of the two phases (I and II). The anionic network is in the form of [Cd2I6]2− 1D chains, with pyrrolid…
Structural phase transitions coupled with prominent dielectric anomalies and dielectric relaxation in [(CH3)3NH]2[KCo(CN)6] and mixed [(CH3)3NH]2[KFexCo1−x(CN)6] double perovskite hybrids
The crystals of pure [(CH3)3NH]2[KFe(CN)6] (TrMAFe) and [(CH3)3NH]2[KCo(CN)6] (TrMACo) as well as their mixed crystals (TrMAFexCo1−x), with different ratios of x = 0, 0.12, 0.18, 0.49, 0.56, 0.73, 0.81, 1.0, have been grown from aqueous solutions. The structure of TrMACo has been determined at 360 K to be cubic (Fmm). In phase II (100 K), the TrMACo crystal is monoclinic (C2/c). The thermal stability of the pure and mixed crystals has been determined by using both DTA and TGA. Based on the DSC results, we have found a single phase transition (PT) for both pure and mixed crystals. The Fe(III) concentration was estimated by using the SEM technique. We have found a linear relationship between …
Structure and properties of tris(tetramethylammonium) nonabromodiarsenate(III), [(CH3)4N]3[As2Br9]
The new tetramethylammonium bromoarsenate(III) crystal [(CH3)4N]3 [As2Br9] has been synthesized and its phase behaviour established by differential scanning calorimetry and dilatometry. Three phase transitions are found: at 346/346 K , at 165/171 K and at 157/165 K on cooling/heating. Single-crystal x-ray diffraction studies of phases I (at 370 K) and II (at 298 K) have shown that the structure comprises discrete [As2Br9]3− anions and disordered [(CH3)4N]+ cations. Phase II crystallizes in the polar space group P31c; its polar nature was confirmed by pyroelectric measurements. Phase I has higher symmetry, P63mc or . Dielectric dispersion measurements revealed a relaxation process in the cry…
DSC, Dilatometric, Dielectric, and1H NMR Studies of Phase Transitions and Molecular Motions in [N(C2H5)4]3M2Cl9 (M = Sb, Bi) Crystals
Results in the dependence of stoichiometry of obtained tetraethylammonium (TEA) chloroantiomonate and chlorobismuthate salts on the molar ratio of reactants used in the synthesis are presented. Seven tetraethylammonium salts are obtained: (TEA) 6 M 8 Cl 30 , TEAMCI 4 , (TEA) 3 M 2 Cl 9 (M = Sb, Bi) and (TEA) 2 SbCl 5 . Preliminary X-ray diffraction studies on (TEA) 3 M 2 Cl 9 (M = Sb, Bi) show that they are isomorphous, crystallizing at room temperature in monoclinic symmetry. The dilatometric, dielectric, and DSC studies show that (TEA) 3 Bi 2 Cl 9 undergoes two phase transitions at T c2 = 144 K and at T c1 = 322 K while (TEA) 3 Sb 2 Cl 9 undergoes three transitions at T c3 = 185, T c2 = 2…
Isostructural phase transition, quasielastic neutron scattering and magnetic resonance studies of a bistable dielectric ion-pair crystal [(CH3)2NH2]2KCr(CN)6
We have synthesised and characterised a novel organic–inorganic hybrid crystal, [(CH3)2NH2]2KCr(CN)6. The thermal DSC, TMA, DTG and DTA analyses indicate two solid-to-solid structural phase transitions (PTs). According to the X-ray diffraction experiments, the first PT at 220 K is isostructural, since it does not involve a change of the space group. This transition occurs between the states, where the (CH3)2NH2+ cations are orientationally disordered and ordered (frozen). The other reversible PT at 481 K leads to a melt-like phase similar to the one observed in plastic crystals or polar liquids. Dielectric spectroscopy has been used to characterise the switching properties of the dipole mom…
Structure, phase transitions and molecular dynamics in ferroelastic crystal pyrrolidinium hexachloroantimonate(V), [C4H8NH2][SbCl6]
Abstract The crystal structure of the pyrrolidinium hexachloroantimonate(V), [C4H8NH2][SbCl6], abbreviated PCA, has been determined by means of X-ray diffraction at 300 and 340 K. The space groups are monoclinic P 2 1 / n (phase III) and orthorhombic Pmnb (phase II), respectively. The crystal undergoes two structural phase transitions: first-order type at 356/329 K (heating/cooling) from phase (I) to (II) and second-order type at 323 K from phase (II) to (III). Dielectric studies suggest the plastic crystals behaviour above 356 K (phase I). Proton spin-lattice relaxation time ( T 1 ) and second moment ( M 2 ) of polycrystalline [C4H8NH2][SbCl6] have been determined at 77–370 K, at 90 and 25…
The structure, phase transition and molecular dynamics of [C(NH2)3]3[Sb2Br9]
The crystal structures of [C(NH2)3]3[Sb2Br9] (Gu3Sb2Br9) at 300 K and of [C(NH2)3]3[Sb2Cl9] (Gu3Sb2Cl9) at 90 and 300 K are determined. The compounds crystallize in the monoclinic space group: C 2/c. The structure is composed of Sb2X93− (X = Cl, Br) ions, which form two-dimensional layers through the crystal, and guanidinium cations. In Gu3Sb2Br9 the structural phase transformation of the first-order type is detected at 435/450 K (on cooling/heating) by the DSC and dilatometric techniques. The dielectric relaxation process in the frequency range between 75 kHz and 5 MHz over the low temperature phase indicates reorientations of weakly distorted guanidinium cations. The proton 1H NMR second-…
Structure, phase transitions and molecular motions in ferroelastic (C4H8NH2)SbCl6·(C4H8NH2)Cl
The crystal structure at 293 K of the new pyrrolidinium chloroantimonate (V) analogue, (C4H8NH2)SbCl6(C4H8NH2)Cl, has been determined by x-ray diffraction as monoclinic, space group P21/c, Z = 8. The crystal is built up of isolated SbCl6- anions, two types of inequivalent pyrrolidinium cation and isolated Cl- ions. It undergoes five solid-solid phase transitions: at 351/374 K of first-order type (cooling/heating, respectively), at 356 and 152 K second order and at 135/141 and 105/134 K first order, detected by differential scanning calorimetry, dilatometric and dielectric measurements. The ferroelastic domain structure appears between 152 and 135 K. The proton nuclear magnetic resonance sec…
Structure and properties of 2-cyanopyridinium perchlorate [2-CNPyH][ClO4]
The crystal structure of 2-cyanopyridinium perchlorate, [2-CNPyH][ClO4], has been determined at 100 (phase II) and 293 K (phase I). It is monoclinic P 21 at 100 K and orthorhombic P 212121 at 293 K. The dynamic properties of the crystal were studied by differential scanning calorimetry, dilatometry, pyroelectric, dielectric, proton (1H NMR), chlorine (35Cl NMR) magnetic resonance spectroscopies and the infrared method. The crystal undergoes a structural phase transition () at 170 K characterized by a complex mechanism involving both 'order–disorder' and 'displacive' contributions. It reveals pyroelectric properties below 170 K. The dielectric relaxation existing over phase I is due to the m…
Screening Ferroelastic Transitions in Switchable Cyano-Bridged Perovskites: [CH3C(NH2)2]2[KM(CN)6], M = Cr3+, Fe3+, Co3+. Crystal Structure Characterization, Dielectric Properties, 1H NMR, and Quasielastic Neutron Scattering Studies
Here we report the dynamics of organic cations as guest molecules in the novel perovskite host framework. The novel switchable crystals from the coordination family [CH3C(NH2)2]2[KB″(CN)6] were con...
1H NMR, DSC, dielectric, and dilatometric studies of phase transitions and molecular dynamics in N (C2H5)4SbCl4
The results of dielectric, dilatometric, 1H NMR, and DSC studies on N(C2H5)4SbCl4 crystals are presented. The title compound undergoes two phase transitions at Tc1 = 272 K reversible of first order and at Tc2 = 393 K irreversible. The values of transition entropies and enthalpies are compared with those of other tetraethylammonium halogenoantimonates and bismuthates (III). The spin-lattice relaxation times and the values of the second moments of the 1H NMR line for the N(C2H5)4SbCl4 crystal are measured in the temperature range of 70 to 400 K. Two minima of T1 are observed. They are attributed to CH3 group reorientations. The activation energies for the processes are determined.
Structural characterization, thermal, dielectric, vibrational properties and molecular dynamics of (C5H5NH)3BiCl6
Abstract (C5H5NH)3BiCl6 crystallizes at room temperature in the triclinic space group P 1 ¯ . The crystal is built up of the separated BiCl 6 3 - octahedral anions and pyridinium cations. Differential scanning calorimetry (DSC) and dilatometric measurements disclose structural phase transition of first-order type at 265/302 K (cooling/heating). The dielectric investigations reveal a step-wise change of the electric permittivity at Tc characteristic of the crystals with the high-temperature plastic-like phase. Temperature-dependent infrared spectra for polycrystalline samples have been taken between 20 and 306 K to clarify the cation dynamics contribution to the mechanism of the phase transi…
CCDC 1897453: Experimental Crystal Structure Determination
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CCDC 1897452: Experimental Crystal Structure Determination
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