Grazyna Bator - Academia.edu (original) (raw)
Papers by Grazyna Bator
![Research paper thumbnail of Structure and ferroelectric properties of [C3N2H5]5[Bi2Br11]](https://attachments.academia-assets.com/109732913/thumbnails/1.jpg)
](Journal of Physics: Condensed Matter, 2008
A ferroelectric crystal [C 3 N 2 H 5 ] 5 [Bi 2 Br 11 ] has been synthesized and structurally char... more A ferroelectric crystal [C 3 N 2 H 5 ] 5 [Bi 2 Br 11 ] has been synthesized and structurally characterized at 170 and 100 K. The crystal structure consists of discrete corner-sharing bioctahedra [Bi 2 Br 11 ] 5− and highly disordered imidazolium cations. The room temperature crystal structure has been determined as monoclinic, space group, P2 1 /n with: a = 9.257(2)Å, b = 15.157(3)Å, c = 13.865(3)Å and β = 97.73(3) •. The crystal undergoes two solid-solid phase transitions: at 355 K of first-order and at 155 K of second-order type. The later transition takes place between monoclinic phases: P2 1 /n → Pn. The dielectric and pyroelectric measurements allow us to characterize the low temperature phase III as ferroelectric with the Curie temperature at 155 K. The saturated spontaneous polarization of the order of 2.6 × 10 −3 C m −2 was measured along the a-axis (130 K). The ferroelectric phase transition mechanism at 155 K is due to the dynamics of three of five nonequivalent imidazolium cations.
Journal of Molecular Structure, 2012
ABSTRACT Thiazolium cation Sb(III) and Bi(III) X-ray diffraction Dielectric relaxation 1 H NMR a ... more ABSTRACT Thiazolium cation Sb(III) and Bi(III) X-ray diffraction Dielectric relaxation 1 H NMR a b s t r a c t Two thiazolium analogs, (C 3 H 4 NS) 6 Sb 4 Br 18 Á2H 2 O (TBA) and (C 3 H 4 NS) 6 Bi 4 Br 18 Á2H 2 O (TBB), have been syn-thesized and structurally characterized. The compounds appeared to be isomorphous and crystallize in the triclinic symmetry, space group P 1 (at 100 K). These ionic complexes are built up of thiazolium cat-ions, centrosymmetric [M 4 Br 18 ] 6À anions (M = Sb, Bi) and water molecules. One of three independent thiazolium cations was found to be disordered (two-site model). The cations are hydrogen bonded to [M 4 Br 18 ] 6À moieties and water molecules. The water molecule (O w) acts as a donor of the O–HÁ Á ÁBr and an acceptor of the N–HÁ Á ÁO types of hydrogen bonds. The dielectric dispersion studies disclosed a low frequency relaxation process characterized by a significant slowing down of two independent dielec-tric relaxators. The dielectric behavior was explained by the motion of thiazolium cations and water mol-ecules The molecular motions of the thiazolium and water molecules were studied by means of the 1 H NMR spin–lattice relaxation time (T 1) measurements. Ó 2012 Elsevier B.V. All rights reserved.
![Research paper thumbnail of Structure, phase transitions and molecular dynamics in 4-aminopyridinium hexachloroantimonate(V), [4-NH2C5H4NH][SbCl6]](https://attachments.academia-assets.com/109732914/thumbnails/1.jpg)
](Journal of Molecular Structure, 2006
4-Aminopyridinium hexachloroantimonate(V), [4-NH 2 C 5 H 4 NH][SbCl 6 ], abbreviated to 4APCA, cr... more 4-Aminopyridinium hexachloroantimonate(V), [4-NH 2 C 5 H 4 NH][SbCl 6 ], abbreviated to 4APCA, crystallizes at room temperature in the monoclinic system, space group P2 1 /c (phase III). The crystal undergoes two reversible phase transitions of first order type at 386/346 K (II4III) and at 467/466 K (I4II) on heating-cooling runs. Dielectric studies suggest the plastic crystal's behavior above 386 K (phase II). The proton NMR second moment (M 2) and the 1 H NMR spin-lattice relaxation time (T 1) for 4APCA measured between 77 and 420 K revealed the C 2 reorientation of the 4-aminopyridinium cations. The mechanism of the phase transitions in 4APCA at 386 K is discussed.
Ferroelectrics, 1986
ABSTRACT
Solid State Sciences, 2004
ABSTRACT Crystal structure of tetra(4-ethylpyridinium) decachlorodiantimonate(III), [4-C2H5PyH]4[... more ABSTRACT Crystal structure of tetra(4-ethylpyridinium) decachlorodiantimonate(III), [4-C2H5PyH]4[Sb2Cl10], has been determined at 245 K by X-ray diffraction (tetragonal, space group P41212P41212). DSC and dilatometric studies indicate a presence of two reversible phase transitions of the first order type, at 370/373 and 233/238 K (cooling/heating) with ΔS=4.0ΔS=4.0 and 10.1 J mol−1 K−1, respectively. Infrared spectra of polycrystalline [4-C2H5PyH]4[Sb2Cl10] have been studied in the temperature range 20–306 K. Substantial changes in the temperature evolution of frequencies of internal modes of the 4-ethylpyridinium cations near 233 K are due to the ordering of the cationic sublattice. The experimental results indicate that both phase transitions may be classified as the order–disorder ones.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Vibrational Spectroscopy, 2014
Results of inelastic neutron scattering (INS), infra-red (IR), Raman and 1 H NMR spectroscopy use... more Results of inelastic neutron scattering (INS), infra-red (IR), Raman and 1 H NMR spectroscopy used for investigations on the l-asparagine dynamics are reported. The crystallographic structure and experimental vibrational spectra are compared with those calculated by the DFT methods applied to the solid state. Very good conformity of the experimental and theoretical structures has been found. The NH 3 + torsional vibration mode is observed in the INS spectra at 494 cm −1 , while the bands assigned to the vibrations of the strong N H• • •O hydrogen bonds are observed at 2849, 2650, and 2480 cm −1 in the IR spectrum. A 1 H NMR investigation has been carried out at 26.75 MHz in the temperature range 150-300 K. For l-asparagine the activation energy needed for the NH 3 + group reorientation is equal 5.6 kcal/mol.
Spectroscopy Letters, 1997
ABSTRACT
Phase Transitions, 2007
Scaling hypothesis is used to construct the equations of state that provide the experimentally ob... more Scaling hypothesis is used to construct the equations of state that provide the experimentally observed variety of the Curie--Weiss constants ratios (i.e., the ratios of the slopes between the temperature dependencies of inverse of susceptibility below and above the critical point) in uniaxial ferroelectrics. The results are exemplified by the TGS crystal and by the methylammonium salts MAPCB and MAPBB.
![Research paper thumbnail of The phase situation and ferroelectric properties in the mixed crystals [4-NH2PyH][SbCl4(1−x)Br4x]](https://attachments.academia-assets.com/103473666/thumbnails/1.jpg)
](Journal of Molecular Structure, 2008
The group of mixed crystals of general formula: [4-APyH][SbCl 4(1Àx) Br 4x ] with x ranging from ... more The group of mixed crystals of general formula: [4-APyH][SbCl 4(1Àx) Br 4x ] with x ranging from 0 to 1 was studied by means of differential scanning calorimetry, dilatometry and dielectric spectroscopy. The ferroelectric properties are preserved for mixed crystals with replacement fraction, x, less than 0.30. Moreover, such a substitution of the chlorine atoms by the bromine ones significantly lowers the temperature of the structural phase transition shifting it from 240 K for pure [4-APyH][SbCl 4 ] to about 185 K for the mixed crystals richer in bromine. The dielectric relaxation process exhibited by the mixed crystal with x = 0.90 in the radio-frequency region was analyzed and the activation energy was estimated (E a = 18 kJ/mol). Additional measurements of single crystals X-ray diffraction and powder IR and Raman spectroscopy were performed. On the basis of the experimental results the phase diagram for mixed crystals has been proposed.
![Research paper thumbnail of [NH2CHNH2]3Sb2I9: a lead-free and low-toxicity organic–inorganic hybrid ferroelectric based on antimony(iii) as a potential semiconducting absorber](https://attachments.academia-assets.com/103473632/thumbnails/1.jpg)
](Inorganic Chemistry Frontiers, 2020
A novel room-temperature ferroelectric crystal with the complex sequence of phase transitions.
CrystEngComm, 2018
Crystals of tetrafluoroboric acid with tetramethylpyrazine, TMP + HBF4 + H2O (1 : 1 : 2, A), TMP ... more Crystals of tetrafluoroboric acid with tetramethylpyrazine, TMP + HBF4 + H2O (1 : 1 : 2, A), TMP + HBF4 (1 : 1, B) and TMP + HBF4 (1 : 2, C) were synthesized and characterized by physicochemical experimental methods.
![Research paper thumbnail of Multifunctional materials based on the double-perovskite organic–inorganic hybrid (CH3NH3)2[KCr(CN)6] showing switchable dielectric, magnetic, and semiconducting behaviour](https://attachments.academia-assets.com/93873506/thumbnails/1.jpg)
](Dalton Transactions, 2019
Herein, we have synthesised and characterised a novel organic–inorganic hybrid crystal, [CH3NH3]2... more Herein, we have synthesised and characterised a novel organic–inorganic hybrid crystal, [CH3NH3]2KCr(CN)6 (MACr).
Acta Physica Polonica A, 2007
Inelastic neutron scattering infrared and Raman spectra of the crystalline 1,3,5-trimethoxybenzen... more Inelastic neutron scattering infrared and Raman spectra of the crystalline 1,3,5-trimethoxybenzene were measured and compared with simulated ones by using the Gaussian 98 and DMol3 programs at density functional theory methods. Application of the double numerical plus polarization basis set for the crystalline state within the local density Perdew and Wang (PWC functionals) approximation quite well reproduces the low frequency bands related to the methyl group librational modes, which are very sensitive to molecular interactions. Infrared spectra for the crystalline sample and CCl 4 solution show spectacularly the change of low frequency modes by going from the symmetric D 3h molecules in the gas phase to asymmetric ones in the crystal.
Physica Status Solidi (a), 1995
ABSTRACT
Phase Transitions, 2006
The simplest scaling equation of state and its limit case corresponding to the Landau theory turn... more The simplest scaling equation of state and its limit case corresponding to the Landau theory turns out to accurately describe the temperature dependence of the electric susceptibility measured in a biasing static field (Nonlinear Dielectric Effect NDE) in uniaxial ferroelectrics. The same equation of state should be, in principle, valid at the zero-biasing field, in which case the susceptibility is
Journal of Physics: Condensed Matter, 1995
ABSTRACT
Journal of Physics: Condensed Matter, 1999
ABSTRACT
![Research paper thumbnail of Structure and phase transitions in chloroantimonate(V) crystals: [(C2H5)3NH]SbCl6 and [(C2H5)3NH]SbCl6·1/2[(C2H5)3NH]Cl](https://attachments.academia-assets.com/93873510/thumbnails/1.jpg)
](Journal of Physics and Chemistry of Solids, 2002
New triethylammonium salts: [(C 2 H 5) 3 NH]SbCl 6 (TCA) and [(C 2 H 5) 3 NH]SbCl 6´1 /2[(C 2 H 5... more New triethylammonium salts: [(C 2 H 5) 3 NH]SbCl 6 (TCA) and [(C 2 H 5) 3 NH]SbCl 6´1 /2[(C 2 H 5) 3 NH]Cl (TCAT) have been synthesized. The compounds crystallise in monoclinic symmetry: space groups P2 1 /n and P2 1 /c, for TCA at 293 K and TCAT at 100 K, respectively. The crystal structure of [(C 2 H 5) 3 NH]SbCl 6 consists of discrete ionic pairsÐtriethylammonium cations and hexachloroantimonate anionsÐlinked via the bifurcated N±H´´´Cl hydrogen bonds. The crystal structure of [(C 2 H 5) 3 NH]SbCl 6´1 /2[(C 2 H 5) 3 NH]Cl is composed of three symmetrically independent triethylammonium cations, chlorine anion and two symmetrically independent hexachloroantimonate anions. TCA undergoes a structural phase transition at 336 K (on heating) into the orthorhombic C222 space group, whereas TCAT reveals a structural phase transition at 332 K. The phase transitions are of the ®rst order type. TCA shows a ferroelastic domain structure below 336 K. Differential scanning calorimetry, dilatometric, dielectric dispersion and Raman scattering measurements have been used to study the phase transition mechanisms in these triethylammonium salts.
Journal of Physics and Chemistry of Solids, 2000
Three piperidinium analogues: (C 5 H 10 NH 2) 2 BiCl 5 , (C 5 H 10 NH 2) 2 BiBr 5 and (C 5 H 10 N... more Three piperidinium analogues: (C 5 H 10 NH 2) 2 BiCl 5 , (C 5 H 10 NH 2) 2 BiBr 5 and (C 5 H 10 NH 2) 2 SbBr 5 have been studied by means of differential scanning calorimetry, thermal expansion, dielectric and Raman scattering techniques. Each piperidinium salt undergoes one high-temperature structural phase transition, which has been classified as an "order-disorder" type. All transitions are connected with onset of reorientational motion of the organic cations. The X-ray studies on (C 5 H 10 NH 2) 2 BiCl 5 show that it crystallises in orthorhombic Pna2 1 space group. The structure has been refined to R 0:0336: It consists of onedimensional BiCl 2Ϫ 5 n polyanionic chains and two non-equivalent piperidinium cations, one ordered and one disordered. The disorder is realised by splitting all atoms between two positions with half occupancy. The Raman studies of the polycrystalline (C 5 H 10 NH 2) 2 BiCl 5 performed in the frequency region between 3500 and 50 cm Ϫ1 show that the vibrational state of the piperidinium cation changes around the phase transition point.
Journal of Physics: Condensed Matter, 2008
A ferroelectric crystal [C 3 N 2 H 5 ] 5 [Bi 2 Br 11 ] has been synthesized and structurally char... more A ferroelectric crystal [C 3 N 2 H 5 ] 5 [Bi 2 Br 11 ] has been synthesized and structurally characterized at 170 and 100 K. The crystal structure consists of discrete corner-sharing bioctahedra [Bi 2 Br 11 ] 5− and highly disordered imidazolium cations. The room temperature crystal structure has been determined as monoclinic, space group, P2 1 /n with: a = 9.257(2)Å, b = 15.157(3)Å, c = 13.865(3)Å and β = 97.73(3) •. The crystal undergoes two solid-solid phase transitions: at 355 K of first-order and at 155 K of second-order type. The later transition takes place between monoclinic phases: P2 1 /n → Pn. The dielectric and pyroelectric measurements allow us to characterize the low temperature phase III as ferroelectric with the Curie temperature at 155 K. The saturated spontaneous polarization of the order of 2.6 × 10 −3 C m −2 was measured along the a-axis (130 K). The ferroelectric phase transition mechanism at 155 K is due to the dynamics of three of five nonequivalent imidazolium cations.
Journal of Molecular Structure, 2012
ABSTRACT Thiazolium cation Sb(III) and Bi(III) X-ray diffraction Dielectric relaxation 1 H NMR a ... more ABSTRACT Thiazolium cation Sb(III) and Bi(III) X-ray diffraction Dielectric relaxation 1 H NMR a b s t r a c t Two thiazolium analogs, (C 3 H 4 NS) 6 Sb 4 Br 18 Á2H 2 O (TBA) and (C 3 H 4 NS) 6 Bi 4 Br 18 Á2H 2 O (TBB), have been syn-thesized and structurally characterized. The compounds appeared to be isomorphous and crystallize in the triclinic symmetry, space group P 1 (at 100 K). These ionic complexes are built up of thiazolium cat-ions, centrosymmetric [M 4 Br 18 ] 6À anions (M = Sb, Bi) and water molecules. One of three independent thiazolium cations was found to be disordered (two-site model). The cations are hydrogen bonded to [M 4 Br 18 ] 6À moieties and water molecules. The water molecule (O w) acts as a donor of the O–HÁ Á ÁBr and an acceptor of the N–HÁ Á ÁO types of hydrogen bonds. The dielectric dispersion studies disclosed a low frequency relaxation process characterized by a significant slowing down of two independent dielec-tric relaxators. The dielectric behavior was explained by the motion of thiazolium cations and water mol-ecules The molecular motions of the thiazolium and water molecules were studied by means of the 1 H NMR spin–lattice relaxation time (T 1) measurements. Ó 2012 Elsevier B.V. All rights reserved.
Journal of Molecular Structure, 2006
4-Aminopyridinium hexachloroantimonate(V), [4-NH 2 C 5 H 4 NH][SbCl 6 ], abbreviated to 4APCA, cr... more 4-Aminopyridinium hexachloroantimonate(V), [4-NH 2 C 5 H 4 NH][SbCl 6 ], abbreviated to 4APCA, crystallizes at room temperature in the monoclinic system, space group P2 1 /c (phase III). The crystal undergoes two reversible phase transitions of first order type at 386/346 K (II4III) and at 467/466 K (I4II) on heating-cooling runs. Dielectric studies suggest the plastic crystal's behavior above 386 K (phase II). The proton NMR second moment (M 2) and the 1 H NMR spin-lattice relaxation time (T 1) for 4APCA measured between 77 and 420 K revealed the C 2 reorientation of the 4-aminopyridinium cations. The mechanism of the phase transitions in 4APCA at 386 K is discussed.
Ferroelectrics, 1986
ABSTRACT
Solid State Sciences, 2004
ABSTRACT Crystal structure of tetra(4-ethylpyridinium) decachlorodiantimonate(III), [4-C2H5PyH]4[... more ABSTRACT Crystal structure of tetra(4-ethylpyridinium) decachlorodiantimonate(III), [4-C2H5PyH]4[Sb2Cl10], has been determined at 245 K by X-ray diffraction (tetragonal, space group P41212P41212). DSC and dilatometric studies indicate a presence of two reversible phase transitions of the first order type, at 370/373 and 233/238 K (cooling/heating) with ΔS=4.0ΔS=4.0 and 10.1 J mol−1 K−1, respectively. Infrared spectra of polycrystalline [4-C2H5PyH]4[Sb2Cl10] have been studied in the temperature range 20–306 K. Substantial changes in the temperature evolution of frequencies of internal modes of the 4-ethylpyridinium cations near 233 K are due to the ordering of the cationic sublattice. The experimental results indicate that both phase transitions may be classified as the order–disorder ones.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Vibrational Spectroscopy, 2014
Results of inelastic neutron scattering (INS), infra-red (IR), Raman and 1 H NMR spectroscopy use... more Results of inelastic neutron scattering (INS), infra-red (IR), Raman and 1 H NMR spectroscopy used for investigations on the l-asparagine dynamics are reported. The crystallographic structure and experimental vibrational spectra are compared with those calculated by the DFT methods applied to the solid state. Very good conformity of the experimental and theoretical structures has been found. The NH 3 + torsional vibration mode is observed in the INS spectra at 494 cm −1 , while the bands assigned to the vibrations of the strong N H• • •O hydrogen bonds are observed at 2849, 2650, and 2480 cm −1 in the IR spectrum. A 1 H NMR investigation has been carried out at 26.75 MHz in the temperature range 150-300 K. For l-asparagine the activation energy needed for the NH 3 + group reorientation is equal 5.6 kcal/mol.
Spectroscopy Letters, 1997
ABSTRACT
Phase Transitions, 2007
Scaling hypothesis is used to construct the equations of state that provide the experimentally ob... more Scaling hypothesis is used to construct the equations of state that provide the experimentally observed variety of the Curie--Weiss constants ratios (i.e., the ratios of the slopes between the temperature dependencies of inverse of susceptibility below and above the critical point) in uniaxial ferroelectrics. The results are exemplified by the TGS crystal and by the methylammonium salts MAPCB and MAPBB.
Journal of Molecular Structure, 2008
The group of mixed crystals of general formula: [4-APyH][SbCl 4(1Àx) Br 4x ] with x ranging from ... more The group of mixed crystals of general formula: [4-APyH][SbCl 4(1Àx) Br 4x ] with x ranging from 0 to 1 was studied by means of differential scanning calorimetry, dilatometry and dielectric spectroscopy. The ferroelectric properties are preserved for mixed crystals with replacement fraction, x, less than 0.30. Moreover, such a substitution of the chlorine atoms by the bromine ones significantly lowers the temperature of the structural phase transition shifting it from 240 K for pure [4-APyH][SbCl 4 ] to about 185 K for the mixed crystals richer in bromine. The dielectric relaxation process exhibited by the mixed crystal with x = 0.90 in the radio-frequency region was analyzed and the activation energy was estimated (E a = 18 kJ/mol). Additional measurements of single crystals X-ray diffraction and powder IR and Raman spectroscopy were performed. On the basis of the experimental results the phase diagram for mixed crystals has been proposed.
Inorganic Chemistry Frontiers, 2020
A novel room-temperature ferroelectric crystal with the complex sequence of phase transitions.
CrystEngComm, 2018
Crystals of tetrafluoroboric acid with tetramethylpyrazine, TMP + HBF4 + H2O (1 : 1 : 2, A), TMP ... more Crystals of tetrafluoroboric acid with tetramethylpyrazine, TMP + HBF4 + H2O (1 : 1 : 2, A), TMP + HBF4 (1 : 1, B) and TMP + HBF4 (1 : 2, C) were synthesized and characterized by physicochemical experimental methods.
Dalton Transactions, 2019
Herein, we have synthesised and characterised a novel organic–inorganic hybrid crystal, [CH3NH3]2... more Herein, we have synthesised and characterised a novel organic–inorganic hybrid crystal, [CH3NH3]2KCr(CN)6 (MACr).
Acta Physica Polonica A, 2007
Inelastic neutron scattering infrared and Raman spectra of the crystalline 1,3,5-trimethoxybenzen... more Inelastic neutron scattering infrared and Raman spectra of the crystalline 1,3,5-trimethoxybenzene were measured and compared with simulated ones by using the Gaussian 98 and DMol3 programs at density functional theory methods. Application of the double numerical plus polarization basis set for the crystalline state within the local density Perdew and Wang (PWC functionals) approximation quite well reproduces the low frequency bands related to the methyl group librational modes, which are very sensitive to molecular interactions. Infrared spectra for the crystalline sample and CCl 4 solution show spectacularly the change of low frequency modes by going from the symmetric D 3h molecules in the gas phase to asymmetric ones in the crystal.
Physica Status Solidi (a), 1995
ABSTRACT
Phase Transitions, 2006
The simplest scaling equation of state and its limit case corresponding to the Landau theory turn... more The simplest scaling equation of state and its limit case corresponding to the Landau theory turns out to accurately describe the temperature dependence of the electric susceptibility measured in a biasing static field (Nonlinear Dielectric Effect NDE) in uniaxial ferroelectrics. The same equation of state should be, in principle, valid at the zero-biasing field, in which case the susceptibility is
Journal of Physics: Condensed Matter, 1995
ABSTRACT
Journal of Physics: Condensed Matter, 1999
ABSTRACT
Journal of Physics and Chemistry of Solids, 2002
New triethylammonium salts: [(C 2 H 5) 3 NH]SbCl 6 (TCA) and [(C 2 H 5) 3 NH]SbCl 6´1 /2[(C 2 H 5... more New triethylammonium salts: [(C 2 H 5) 3 NH]SbCl 6 (TCA) and [(C 2 H 5) 3 NH]SbCl 6´1 /2[(C 2 H 5) 3 NH]Cl (TCAT) have been synthesized. The compounds crystallise in monoclinic symmetry: space groups P2 1 /n and P2 1 /c, for TCA at 293 K and TCAT at 100 K, respectively. The crystal structure of [(C 2 H 5) 3 NH]SbCl 6 consists of discrete ionic pairsÐtriethylammonium cations and hexachloroantimonate anionsÐlinked via the bifurcated N±H´´´Cl hydrogen bonds. The crystal structure of [(C 2 H 5) 3 NH]SbCl 6´1 /2[(C 2 H 5) 3 NH]Cl is composed of three symmetrically independent triethylammonium cations, chlorine anion and two symmetrically independent hexachloroantimonate anions. TCA undergoes a structural phase transition at 336 K (on heating) into the orthorhombic C222 space group, whereas TCAT reveals a structural phase transition at 332 K. The phase transitions are of the ®rst order type. TCA shows a ferroelastic domain structure below 336 K. Differential scanning calorimetry, dilatometric, dielectric dispersion and Raman scattering measurements have been used to study the phase transition mechanisms in these triethylammonium salts.
Journal of Physics and Chemistry of Solids, 2000
Three piperidinium analogues: (C 5 H 10 NH 2) 2 BiCl 5 , (C 5 H 10 NH 2) 2 BiBr 5 and (C 5 H 10 N... more Three piperidinium analogues: (C 5 H 10 NH 2) 2 BiCl 5 , (C 5 H 10 NH 2) 2 BiBr 5 and (C 5 H 10 NH 2) 2 SbBr 5 have been studied by means of differential scanning calorimetry, thermal expansion, dielectric and Raman scattering techniques. Each piperidinium salt undergoes one high-temperature structural phase transition, which has been classified as an "order-disorder" type. All transitions are connected with onset of reorientational motion of the organic cations. The X-ray studies on (C 5 H 10 NH 2) 2 BiCl 5 show that it crystallises in orthorhombic Pna2 1 space group. The structure has been refined to R 0:0336: It consists of onedimensional BiCl 2Ϫ 5 n polyanionic chains and two non-equivalent piperidinium cations, one ordered and one disordered. The disorder is realised by splitting all atoms between two positions with half occupancy. The Raman studies of the polycrystalline (C 5 H 10 NH 2) 2 BiCl 5 performed in the frequency region between 3500 and 50 cm Ϫ1 show that the vibrational state of the piperidinium cation changes around the phase transition point.