Narrowing of the 35Cl NQR Lines of Trichloroacetamide Caused by Its Ferroelectric Phase Transition

1990 ◽  
Vol 45 (3-4) ◽  
pp. 327-333 ◽  
Author(s):  
Masao Hashimoto ◽  
Akiko Shono ◽  
Yoshiyuki Mido ◽  
Haruo Niki ◽  
Hiroshi Hentona ◽  
...  
Keyword(s):  
Phase Transition ◽  
Dielectric Behavior ◽  
High Temperature Phase ◽  
Monoclinic Space Group ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
X Ray ◽  
H Nmr ◽  
35Cl Nqr

Abstract Dielectric measurements on single crystals and DSC of the title compound (monoclinic, space group P21) revealed a ferroelectric transition at ca. 355 K (ΔH ≈ 0.5 kJ mol-1) Powder x-ray diffraction indicated that the high temperature phase is also monoclinic and the change in volume at the transition is very small. A displacement of hydrogen atoms is considered as responsible for the appearance of ferroelectricity. The 35Cl NQR signals at ca. 77 K were considerably broad, but a drastic narrowing took place after the compound had once experienced the phase transition. A tentative assignment of the NQR spectrum was made from a calculation of the NQR frequencies based on the CNDO/2 method. Another phase transition was evidenced by a small drift of the DSC curve and a slight anomaly of the dielectric behavior around 358 K. The present 1H NMR experiments gave no indication of the onset of torsional motion of the NH2 group reported to occur at ca. 210 K.

scholarly journals Studies of Structure and Phase Transition in [C(NH2)3]HgBr3 and [C(NH2)3]HgI3 by Means of Halogen NQR, 1H NMR, and Single Crystal X-Ray Diffraction

2000 ◽  
Vol 55 (1-2) ◽  
pp. 230-236 ◽  
Author(s):  
Hiromitsu Terao ◽  
Masao Hashimoto ◽  
Shinichi Hashimoto ◽  
Yoshihiro Furukawa
Keyword(s):  
Phase Transition ◽  
Room Temperature ◽  
Monoclinic Space Group ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Order ◽  
H Nmr ◽  
Trigonal Bipyramidal ◽  
Second Order Phase Transition

(TThe crystal structure of [C(NH2)3]HgBr3 was determined at room temperature: monoclinic, space group C2/c, Z = 4, a = 775.0(2), b = 1564.6(2), c = 772.7(2) pm, β = 109.12(2)°. In the crystal, almost planar HgBr3- ions are connected via Hg ··· Br bonds, resulting in single chains of trigonal bipyramidal HgBr5 units which run along the c direction. [C(NH2)3]HgI3 was found to be isomorphous with the bromide at room temperature. The temperature dependence of the halogen NQR frequencies (77 < 77K < ca. 380) and the DTA measurements evidenced no phase transition for the bromide, but a second-order phase transition at (251 ± 1) K (Tc1) and a first-order one at (210 ± 1) K for the iodide. The transitions at Tc2are accompanied with strong supercooling and significant superheating. The room temperature phase (RTP) and the intermediate temperature phase (ITP) of the iodide are characterized by two 127I(m=1/2↔3/2) NQR lines which are assigned to the terminal and the bridging I atoms, respectively. There exist three lines in the lowest temperature phase (LTP), indicating that the resonance line of the bridging atom splits into two. The signal intensities of the 127I(m =1/2↔3/2) NQR lines in the LTP decrease with decreasing temperature resulting in no detection below ca. 100 K. The 127I(m=1/2↔3/2) NQR frequency vs. temperature curves are continuous at Tcl, but they are unusual in the LTP. The T1vs. Tcurves of 1H NMR for the bromide and iodide are explainable by the reorientational motions of the cations about their pseudo three-fold axes. The estimated activation energies of the motions are 35.0 kJ/mol for the bromide, and 24.1, 30.1, and 23.0 kJ/mol for the RTP, FTP, and LTP of the iodide, respectively

scholarly journals High-temperature phase transition of SrRuO3and SrHfO5: X-ray diffraction and PAC spectroscopy

1996 ◽  
Vol 52 (a1) ◽  
pp. C364-C364
Author(s):  
J. A. Guevara ◽  
S. L. Cuffini ◽  
Y. P. Mascarenhas ◽  
P. de la Presa ◽  
A. Ayala ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Pac Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Phase Transition

On the Phase Transition of Bis(pyridinium)hexachlorometallates, (C5H5NH)2[MCl6], M = Sn, Te, Pb, Pt. An X-Ray and 35Cl NQR Study

1987 ◽  
Vol 42 (7) ◽  
pp. 739-748 ◽  
Author(s):  
Dirk Borchers ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Phase Ii ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray ◽  
Lattice Constants ◽  
Pyridinium Ring ◽  
35Cl Nqr ◽  
Low Temperature Phase

A phase transition has been observed in bis(pyridinium) hexachlorometallates (C5H5NH)2[MIVCl6]. M = Sn. Te. Pb. Pt. The crystal structure of the low temperature phase II of the salt with M = Sn was determined, space group C 1ḷ- P 1̅, Z = 1 (a = 734.1pm, b = 799.0 pm, c = 799.7 pm,α= 83.229°. β = 65.377°, γ= 84.387°, T = 297 K). The four compounds are isotypic in phase II as well as in the high temperature phase I (C2H2-B2 /m, Z = 2) for which the crystal structure is known for M = Te . The lattice constants of all compounds (both phases) are given. The temperature dependence of the 35Cl NQR spectrum was investigated. The three line 35Cl NQR spectrum is in agreement with the crystal structure. The dynamics of the pyridinium ring shows up in a fade out of part of the 35Cl NQR spectrum . The influence o f H ↔ D exchange on 35Cl NQR is studied and an assignment of ν (35Cl) ↔ Cl(i) is proposed. The nature of the phase transition P1̅ (Z = 1) ↔ B2 /m (Z = 2) is discussed.

High-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type PbTiO3phases

2016 ◽  
Vol 72 (3) ◽  
pp. 381-388 ◽  
Author(s):  
Akira Yoshiasa ◽  
Tomotaka Nakatani ◽  
Akihiko Nakatsuka ◽  
Maki Okube ◽  
Kazumasa Sugiyama ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Single Crystal ◽  
Diffraction Study ◽  
Relative Displacement ◽  
High Temperature Phase ◽  
Cubic Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray

A high-temperature single-crystal X-ray diffraction study of a synthetic PbTiO3perovskite was carried out over the wide temperature range 298–928 K. A transition from a tetragonal (P4mm) to a cubic (Pm \bar 3 m) phase has been revealed near 753 K. In the non-centrosymmetricP4mmsymmetry group, the difference in relative displacement between Pb and O along thec-axis is much larger than that between Ti and O. The Pb and Ti cations contribute sufficiently to polarization being shifted in the opposite direction compared with the shift of O atoms. Deviation from the linear changes in Debye–Waller factors and bonding distances in the tetragonal phases can be interpreted as a precursor phenomenon before the phase transition. Disturbance of the temperature factorUeqfor O is observed in the vicinity of the transition point, whileUeqvalues for Pb and Ti are continuously changing with increasing temperature. The O site includes the clear configurational disorder in the cubic phase. The polar local positional distortions remain in the cubic phase and are regarded as the cause of the paraelectricity. Estimated values of the Debye temperature ΘDfor Pb and Ti are 154 and 467 K in the tetragonal phase and decrease 22% in the high-temperature phase. Effective potentials for Pb and Ti change significantly and become soft after the phase transition.

scholarly journals Inorganic Anion Regulates the Phase Transition in Two Organic Cation Salts Containing [(4-Nitroanilinium)(18-crown-6)]+ Supramolecules

2017 ◽  
Author(s):  
Yuan Chen ◽  
Yang Liu ◽  
Binzu Gao ◽  
Chuli Zhu ◽  
Zunqi Liu
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Variable Temperature ◽  
Structural Phase ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Space Group ◽  
X Ray

Two novel inorganic&ndash;organic hybrid supramolecular assemblies, namely, (4-HNA)(18-crown-6)(HSO4) (1) and (4-HNA)2(18-crown-6)2(PF6)2(CH3OH) (2) (4-HNA = 4-nitroanilinium), were synthesized and characterized by infrared spectroscopy, single X-ray diffraction, differential scanning calorimetry (DSC), and temperature-dependent dielectric measurements. The two compounds underwent reversible phase transitions at about 255 K and 265 K, respectively. These phase transitions were revealed and confirmed by the thermal anomalies in DSC measurements and abrupt dielectric anomalies during heating. The phase transition may have originated from the [(4-HNA)(18-crown-6)]+ supramolecular cation. The inorganic anions tuned the crystal packings and thus influenced the phase-transition points and types. The variable-temperature X-ray diffraction data for crystal 1 revealed the occurrence of a phase transition in the high-temperature phase with the space group of P21/c and in the low-temperature phase with the space group of P21/n. Crystal 2 exhibited the same space group P21/c at different temperatures. The results indicated that crystals 1 and 2 both underwent an iso-structural phase transition.

Crystal Structure and Phase Transition of 4-Aminopyridinium Tetrabromoantimonate(III) as Studied by Bromine and Antimony NQR, Proton NMR, and Single Crystal X-Ray Diffraction

2000 ◽  
Vol 55 (1-2) ◽  
pp. 167-172 ◽  
Author(s):  
Masao Hashimoto ◽  
Shinichi Hashimoto ◽  
Hiromitsu Terao ◽  
Masayuki Kuma ◽  
Haruo Niki ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Monoclinic Space Group ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Reorientational Motion ◽  
H Nmr ◽  
Crystal Dynamics ◽  
Motional Narrowing ◽  
Low Temperature Phase

The crystal structure of the room temperature phase (RTP) of the title compound was determined at 297 K (monoclinic, space group C2/c, a = 1384.2(2), b = 1377.8(3), c = 755.5(2) pm, β = 121.58(1)°). A complicated disorder was found for the cation. A phase transition from the low-temperature phase (LTP) to the RTP was found at (224 ±1) K (Tc). The 1H NMR spectra showed a sharp motional narrowing at ca. T=Tc , indicating the occurrence of a reorientational motion of the cation in the RTP in accord with the disorder. It was found that another reorientational motion is excited in the LTP. Four 81Br NQR lines (132.71, 115.38, 61.54 and 59.31 MHz at 77 K) and two Sb NQR lines (53.78 and 33.76 MHz at 77 K) were found in the LTP, while a single 81Br NQR line was observed at T> 276 K (ca. 121.80 MHz at 300 K). Crystal dynamics are discussed on the basis of the temperature dependence of the NQR, 1H NMR line width, and 1H NMR T1.

Powder Diffraction Data of Polymorphic Phases of Dicesium Cadmium Tetraiodide Cs2CdI4

1986 ◽  
Vol 1 (2) ◽  
pp. 35-36 ◽  
Author(s):  
V. Touchard ◽  
M. Louër ◽  
D. Louër
Keyword(s):  
Phase Transition ◽  
Thermal Analysis ◽  
Room Temperature ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Indexing Methods ◽  
X Ray ◽  
Two Phases

Introduction: Phase transition has been recently observed in Cs2CdI4 (Touchard, Louër, Auffrédic & Louër, 1986). Thermal analysis has shown that the transformation occurs at 122°C. By quenching, the high temperature phase (β) can be stabilized at room temperature. In the present work we report the X-ray diffraction powder data, at room temperature, for the two phases α- and β-Cs2CdI4. Both phases have been indexed automatically by using powder indexing methods.

Phase Transitions and Distortion of [BiCl6]3– Octahedra in (C3H5NH3)3[BiCl6] – DSC and Single-Crystal X-Ray Diffraction Studies

2004 ◽  
Vol 59 (9) ◽  
pp. 1029-1034 ◽  
Author(s):  
Bartosz Zarychta ◽  
Maciej Bujak ◽  
Jacek Zaleski
Keyword(s):  
Phase Transition ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Unit Cells ◽  
Temperature Phase Transition ◽  
The Relationship ◽  
Low Temperature Phase ◽  
Disorder Type

The DSC diagram of tris(allylammonium) hexachlorobismuthate(III), (C3H5NH3)3[BiCl6], revealed three anomalies at 152, 191 and 299 K. The structure of the salt was determined at 200 and 315 K, below and above the high-temperature phase transition at 299 K. In both phases the crystals are monoclinic. At 200 K the space group is C2/c whereas at 315 K it is C2/m. The structures, at both temperatures, are composed of [BiCl6]3− octahedra and allylammonium cations. The organic and inorganic moieties are attracted to each other by a network of the N-H. . .Cl hydrogen bonds. The relationship between corresponding parameters of the unit cells has been found. The phase transition at 299 K, of the order-disorder type, is attributed to the ordering of one non-equivalent allylammonium cation in the low-temperature phase.

Synthesis and Characterization of Lithium Ion Conductors, Li3InBr6 and their Substituted Compounds

2005 ◽  
Vol 242-244 ◽  
pp. 17-26
Author(s):  
Yasumasa Tomita ◽  
Hideyoshi Matsushita ◽  
Yasuhisa Maeda ◽  
Kenkichiro Kobayashi ◽  
Koji Yamada
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Lithium Ion ◽  
Substitution Effect ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Li Ion ◽  
Lithium Ion Conductors

Li3-2xMxInBr6 (M=Mg, Ca, Sr and Ba) and Li3In1-xMxBr6 was synthesized, and thier substitution effect was investigated by means of 7Li and 115In NMR, X-ray diffraction and AC conductivity measurements. Phase transition was observed at 314 K in Li3InBr6 and fast Li+ diffusion was observed in the high temperature phase. Li3InBr6 has high Li+ ion conductivity and showed a little difference in X-ray diffraction patterns between the low-temperature phase and the high-temperature phase. These indicate that the sub-lattice for Li+ ions changed largely at the phase transition point and this change makes Li+ diffusion easily. In the high temperature phase of substituted compounds, the conductivity decreased with the amounts of substitution. and defects produced by the substitution with divalent cation did not contribute to the Li+ ion conduction. In the LT phase for Mg compound, the ionic conductivity increases up to x = 0.4 due to the introduction of the extrinsic vacancies.

Tetraalkylammonium Tetrachlorothallates (III); X-Ray, 35Cl-NQR, and 1H-NMR Studies

1991 ◽  
Vol 46 (9) ◽  
pp. 777-784 ◽  
Author(s):  
Marco Lenck ◽  
Shi-qi Dou ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Ii ◽  
Room Temperature ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Nmr Studies ◽  
X Ray ◽  
H Nmr ◽  
35Cl Nqr ◽  
Low Temperature Phase

AbstractThe crystal structure of (CH3)4NTlCl4 and (C2H5)4NTlCl4 was determined at room temperature by single crystal technique. (CH3)4NTlCl4: D2h17-Cmmm; Z = 2; a = 913.2pm, b = 894.6 pm, c = 752.5 pm; (C2H5)4NTlCl4: C6v4-P63mc; Z = 2; a = 827.9 pm, c = 1329.8 pm. (C2H5)4NTlCl4 is isomorphous with (C2H5)4NInCl4. The compounds undergoe a phase transition at 239 K and 222 K, respectively. For both compounds no35 Cl NQR signal was observable in the high temperature phase I due to the dynamics of the anion. The 35 Cl NQR was studied in the low temperature phase II of both compounds as a function of temperature. (CH3)4NTlCl4 shows a two line, (C2H5)4NTlCl4 a four line spectrum. The possible phase II structures and the dynamics of the cation, studied by 1H-NMR, are discussed

Sign in / Sign up

Export Citation Format

Share Document