81Br NQR and 1H NMR of Guanidinium Hexabromoantimonate(V) [C(NH2)3]SbBr6: Phase Transition and Molecular Motion

2002 ◽  
Vol 57 (6-7) ◽  
pp. 399-402 ◽  
Author(s):  
Yoshihiro Furukawa ◽  
Hiromitsu Terao
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Temperature Dependence ◽  
1H Nmr ◽  
Room Temperature ◽  
Molecular Motion ◽  
Thermal Hysteresis ◽  
Temperature Behavior ◽  
H Nmr ◽  
81Br Nqr

Guanidinium hexabromoantimonate(V) [C(NH2)3]SbBr6 was prepared. It was black in color at room temperature and showed a tendency to turn yellow by loosing bromine in open air. Six 81Br NQRlines were observed at 77K.On heating, four of the six lines faded out around 200 K,while the remaining two lines could be observed up to room temperature. This temperature behavior suggests a preferential libration or reorientation around a pseudo C4 axis of the octahedral [SbBr6]- anion. DTA measurement revealed a small heat anomaly at Tc1 = 273 K (on heating), showing a thermal hysteresis, and a sharp and large anomaly at Tc2 = 314 K. The temperature dependence curve of 1H NMR T1 is characterized by a single minimum of 26 ms (32 MHz) near 280 K, which is assigned to the C3 reorientation of the planar [C(NH2)3]+ cations. Its activation energy ( a) is 43.3 kJ/mol

81Br NQR and 1H NMR of Ethylammonium Tetrabromomercurate (II) (C2H5NH3)2HgBr4: Phase Transition and Molecular Motion

2002 ◽  
Vol 57 (6-7) ◽  
pp. 369-374 ◽  
Author(s):  
H. Terao ◽  
Y. Furukawa ◽  
M. Hashimoto ◽  
K. Yamada ◽  
T. Okuda
Keyword(s):  
Phase Transition ◽  
1H Nmr ◽  
Molecular Motion ◽  
81Br Nqr

1H NMR Studies on the Cation Motions in Crystalline Cadmium Bromide Complexes [C(NH2)3]Cd2Br5, [(CH3)3NH]3Cd2Br7, and [i-C3H7NH3]CdBr3

2010 ◽  
Vol 65 (4) ◽  
pp. 499-502 ◽  
Author(s):  
Hideta Ishihara ◽  
Keizo Horiuchi ◽  
Yoshihiro Furukawa
Keyword(s):  
Activation Energy ◽  
1H Nmr ◽  
Molecular Motion ◽  
Higher Order ◽  
Methyl Groups ◽  
Nmr Studies ◽  
H Nmr ◽  
Cadmium Bromide

1H NMR T1 measurements of crystalline [C(NH2)3]Cd2Br5 showed a single minimum due to the C3 reorientation of the planar [C(NH2)3]+ ion with an activation energy (Ea) of 35.8 kJ mol−1. In [(CH3)3NH]3Cd2Br7 crystals, two T1 minima appeared which are assigned to the C3 reorientation of methyl groups in the [(CH3)3NH]+ cation with Ea = 13.0 kJ mol−1 and to the C3 reorientation of a whole cation around the molecular C3 axis with Ea = 28.9 kJ mol−1. In [i-C3H7NH3]CdBr3 crystals, a very broad T1 minimum appeared near 160 K which is assigned to the C3 reorientations of two methyl groups with Ea = 11.3 kJ mol−1 and of an NH3 group with Ea = 13.3 kJ mol−1 in the [i-C3H7NH3]+ ion, and another minimum with Ea = 23.5 kJ mol−1 near 300 K assigned to a higher order molecular motion of the cation.

Phase Transition and Crystal Dynamics of 4-Bromobenzyl Alcohol

1998 ◽  
Vol 53 (6-7) ◽  
pp. 436-441 ◽  
Author(s):  
Masao Hashimoto ◽  
Yuko Monobe ◽  
Hiromitsu Terao ◽  
Haruo Niki ◽  
Koichi Mano
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Phase I ◽  
Temperature Dependence ◽  
Low Temperatures ◽  
Room Temperature ◽  
Molecular Motion ◽  
Dielectric Dispersion ◽  
Compound A ◽  
Crystal Dynamics

Abstract For the title compound a phase transition from Phase II to Phase I (low and room temperature phases, respectively) was found at ca. 217 K. The temperature dependence of the 81Br NQR frequency and that of the dielectric constant showed anomalies at ca. 195 K that were tentatively attributed to a higher order phase transition. A similar anomaly was found at ca. 218 K for 4-chlorobenzyl alcohol which showed a II-I transition at 236 K. The dielectric dispersion observed for both compounds at low temperatures indicates an excitation of a molecular motion with the dielectric relaxation rate of ca. 1 kHz. The temperature dependence of the 81Br NQR frequencies of 2-and 3-bromobenzyl alcohol, measured at T > 77 K, gave no evidence of phase transition in their crystals.

Phase Diagram of the Orientationally Order-disorder Binary System 2,2-dimethyl-1,3-propanediol / 2,2-dimethyl-1,3-diaminopropane, [(CH3)2 C(CH2OH)2]x [(CH3)2C(CH2NH2)2]1-x · A Thermodynamic, X-ray, and 1H-NMR study

1996 ◽  
Vol 51 (7) ◽  
pp. 871-881 ◽  
Author(s):  
Roman Strauss ◽  
Sigmar Braun ◽  
Shi-qi Dou ◽  
Hartmut Fuess ◽  
Alarich Weiss
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Binary System ◽  
Phase I ◽  
1H Nmr ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lattice Constants ◽  
H Nmr

AbstractThe phase diagram of the binary system [2,2-dimethyl-1,3-propanediol]x (1) / [2,2-dimethyl-1,3- diaminopropane]1-x (2) was studied by X-ray diffraction and DTA/DSC, for (2) also by 1H-NMR. The system is miscible over the whole concentration range 0 ≤ x ≤ 1 in the liquid state and in the plastic solid state, phase I, just below the melting point. At lower temperatures the system is demixing, and at room temperature two plastic mixed crystals coexist. The plastic phases of (1), (2), and (l)x(2)1-x crystallize face centered cubic, Fm3m, Z = 4, the lattice constants decreasing linearely with increasing x, and the lattice constants are: (1) a(327K) = 880.3 pm , (2) a(243K) = 905.6 pm. By single crystal X-ray diffraction the structure of the ordered phase II of (1) was refined at room temperature, monoclinic, P21/n, Z = 4, a = 596.9 pm, b = 1090.2 pm, c = 1011.0 pm, β = 99.74°. The results are in good agreement with the literature. The phase transition temperatures (in Kelvin) are T1→m = 399.2, TMm→1 = 399.7, T11→1 = 316.2, T1→11 = 308.2 for (1); = 300.2, = 301.7, T11→1 = 228.7, T1→n = 194.2 for (2). Strong hysteresis is observed for the transition T1→11 in (2). In the mixed systems (1)x(2)1-x, 0 < x < 1, the disordered phases do not order even by quenching to liquid nitrogen temperature. High resolution 1 H-NMR measurements are reported for phase I of (2) as a function of temperature. The “liquid” 1H-NMR spectrum is present far below the thermodynamic phase transition temperature T11-1, overlapping the wide line unresolved powder spectrum of phase II.

NQR and Crystal Structure of 4,5-Dichloroimidazole, C3H2N2Cl2

1992 ◽  
Vol 47 (1-2) ◽  
pp. 177-181 ◽  
Author(s):  
Shi-Qi Dou ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Unit Cell ◽  
Space Group ◽  
Temperature Range ◽  
Temperature Coefficients ◽  
Group D

AbstractThe two line 35Cl NQR spectrum of 4,5-dichloroimidazole was measured in the temperature range 77≦ T/K ≦ 389. The temperature dependence of the NQR frequencies conforms with the Bayer model and no phase transition is indicated in the curves v ( 35Cl)= f(T). Also the temperature coefficients of the 35Cl NQR frequencies are "normal". At 77 K the 35Cl NQR frequencies are 37.409 MHz and 36.172 MHz and at 389 K 35.758 MHz and 34.565 MHz. The compound crystallizes at room temperature with the tetragonal space group D44-P41212, Z = 8 molecules per unit cell; at 295 K : a = 684.2(5) pm, c = 2414.0(20) pm. The relations between the crystal structure and the NQR spectrum are discussed.

Study on the Melting Mechanism of Maleic Anhydride

2020 ◽  
Vol 10 (1) ◽  
pp. 65-78
Author(s):  
Bratati Das ◽  
Ashis Bhattacharjee
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Maleic Anhydride ◽  
Temperature Dependence ◽  
Growth Models ◽  
Melting Process ◽  
Nucleation And Growth ◽  
Crystalline Solid ◽  
Scanning Calorimetry ◽  
Melting Mechanism

Background: Melting of a pure crystalline material is generally treated thermodynamically which disregards the dynamic aspects of the melting process. According to the kinetic phenomenon, any process should be characterized by activation energy and preexponential factor where these kinetic parameters are derivable from the temperature dependence of the process rate. Study on such dependence in case of melting of a pure crystalline solid gives rise to a challenge as such melting occurs at a particular temperature only. The temperature region of melting of pure crystalline solid cannot be extended beyond this temperature making it difficult to explore the temperature dependence of the melting rate and consequently the derivation of the related kinetic parameters. Objective: The present study aims to explore the mechanism of the melting process of maleic anhydride in the framework of phase transition models. Taking this process as just another first-order phase transition, occurring through the formation of nuclei of new phase and their growth, particular focus is on the nucleation and growth models. Methods: Non-isothermal thermogravimetry, as well as differential scanning calorimetry studies, has been performed. Using isoconversional kinetic analysis, temperature dependence of the activation energy of melting has been obtained. Nucleation and growth models have been utilized to obtain the theoretical temperature dependencies for the activation energy of melting and these dependencies are then compared with the experimentally estimated ones. Conclusion: The thermogravimetry study indicates that melting is followed by concomitant evaporation, whereas the differential scanning calorimetry study shows that the two processes appear in two different temperature regions, and these differences observed may be due to the applied experimental conditions. From the statistical analysis, the growth model seems more suitable than the nucleation model for the interpretation of the melting mechanism of the maleic anhydride crystals.

Piezoelectric Properties and Depolarization Temperature of NaNbO3-LiNbO3 Lead-Free Piezoelectric Ceramics

2008 ◽  
Vol 388 ◽  
pp. 233-236 ◽  
Author(s):  
Rintaro Aoyagi ◽  
Makoto Iwata ◽  
Masaki Maeda
Keyword(s):  
Phase Transition ◽  
Room Temperature ◽  
Electromechanical Coupling ◽  
Thermal Hysteresis ◽  
Longitudinal Mode ◽  
Electromechanical Coupling Factor ◽  
Coupling Factor ◽  
Depolarization Temperature ◽  
Higher Temperature ◽  
Curie Temperature Tc

Piezoelectric and dielectric properties of (LixNa1-x)NbO3 (LNN100x; x≤0.14) ceramics were investigated according to phase transition The highest electromechanical coupling factor, kp, of 0.247 was obtained for LNN12 which has a composition with a morphotropic phase boundary at room temperature. On the other hand, the coupling factor of k33 with longitudinal mode was almost constant for all compositions of x. The dielectric constant, ε r, before poling treatment exhibited a thermal hysteresis near the Curie temperature, TC, for all compositions. The depolarization temperature of LNN6 was higher than the TC before poling treatment. In addition, the peak of free permittivity, ε33 T, was shifted to higher temperature. It was considered that the phase transition was induced by the electric field during poling treatment.

scholarly journals Synthesis and characterization of lead-free ternary component BST–BCT–BZT ceramic capacitors

2014 ◽  
Vol 04 (02) ◽  
pp. 1450014 ◽  
Author(s):  
Venkata Sreenivas Puli ◽  
Dhiren K. Pradhan ◽  
Brian C. Riggs ◽  
Shiva Adireddy ◽  
Ram S. Katiyar ◽  
...  
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Energy Density ◽  
Electric Field ◽  
Hysteresis Loop ◽  
Electric Fields ◽  
Room Temperature ◽  
Thermal Hysteresis ◽  
Lead Free ◽  
Maximum Electric Field

Polycrystalline sample of lead-free 1/3( Ba 0.70 Sr 0.30 TiO 3) + 1/3( Ba 0.70 Ca 0.30 TiO 3) + 1/3( BaZr 0.20 Ti 0.80 O 3)( BST - BCT - BZT ) ceramic was synthesized by solid state reaction method. Phase purity and crystal structure of as-synthesized materials was confirmed by X-ray diffraction (XRD). Temperature-dependent dielectric permittivity studies demonstrated frequency-independent behavior, indicating that the studied sample has typical diffuse phase transition behavior with partial thermal hysteresis. A ferroelectric phase transition between cubic and tetragonal phase was noticed near room temperature (~ 330 K). Bulk P–E hysteresis loop showed a saturation polarization of 20.4 μC/cm2 and a coercive field of ~ 12.78 kV/cm at a maximum electric field of ~ 115 kV/cm. High dielectric constant (ε ~ 5773), low dielectric loss (tan δ ~ 0.03) were recorded at room temperature. Discharge energy density of 0.44 J/cm3 and charge energy density of 1.40 J/cm3 were calculated from nonlinear ferroelectric hysteresis loop at maximum electric field. Dielectric constant at variable temperatures and electric fields, ferroelectric to paraelectric phase transition and energy storage properties were thoroughly discussed.

Structure Characteristics of Cubic and Orthorhombic Phases of High Density Scintillator Pbf2 from 4.2–300 K

1994 ◽  
Vol 348 ◽  
Author(s):  
Ivan Shmyt'ko ◽  
I.B. Savchenko ◽  
N.V. Klassen ◽  
B.Sh. Bagautdinov ◽  
G.A. Emel'chenko ◽  
...  
Keyword(s):  
Phase Transition ◽  
Plastic Deformation ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Room Temperature ◽  
Cell Parameter ◽  
Structure Characteristics ◽  
Pseudocubic Phase ◽  
Bulk Single Crystals ◽  
Structural Aspects

ABSTRACTAn anomaly of the temperature dependence of the unit cell parameter has been observed for β–PbF2 single crystals at 200 K that is interpreted as a phase transition to a pseudocubic lattice. Such a pseudocubic phase is observable at room temperature after uniaxial plastic deformation of the bulk single crystals. The structural aspects of the β→α transition have been established. The as-grown crystals of α–PbF2 phase are shown to undergo a phase transition at 100 K.

1H NMR study of the solvolysis of the paramagnetic tetrachloro-bis(imidazole)ruthenium(III) anion in water, methanol, and dimethyl sulfoxide

1995 ◽  
Vol 73 (4) ◽  
pp. 471-482 ◽  
Author(s):  
Craig Anderson ◽  
André L. Beauchamp
Keyword(s):  
Dimethyl Sulfoxide ◽  
1H Nmr ◽  
Room Temperature ◽  
Single Species ◽  
X Ray Diffraction ◽  
Chloro Complexes ◽  
X Ray ◽  
H Nmr ◽  
Nmr Study ◽  
Nmr Signals

The 1H NMR signals of the Ru(III) species present in solution are considerably broadened and shifted by paramagnetism, but they can be used to follow chloride displacement in the trans-[RuCl4Im2]− ion. This anion remains predominant for several hours at room temperature in D2O, but its signals are progressively replaced by those of a monoaqua [RuCl3(D2O)Im2] complex. Over a period of days, two new sets of peaks appear, corresponding to two isomers of [RuCl2(D2O)2Im2]+. The same behaviour is observed for the 1-methyl-and 4-methylimidazole analogues. These reactions can be driven backwards by addition of KCl, but [RuCl4Im2]− is not quantitatively regenerated in solution even for 6 M NaCl. Within several months, the [RuCl2(D2O)2Im2]+ isomers further aquate to a single species [RuCl(D2O)3Im2]2+. In CD3OD, displacement of the first chloride of [RuCl4Im2]− takes place faster, over several hours, but substitution stops at the [RuCl3(CD3OD)Im2] stage. In DMSO, substitution occurs very slowly. The [RuCl3(DMSO)Im2]:[RuCl4Im2]−mixture (1:2) obtained after 12 days starts to show very slow reduction to two Ru(II) species, one of which precipitates as yellow crystals. From X-ray diffraction work (monoclinic, P21/n, a = 9.951, b = 8.564, c = 10.527 Å, β = 92.95°, R = 0.033), the compound was identified as [RuCl2(DMSO-d6)2Im2], where the metal has a trans-trans-trans coordination and the DMSO ligands are S-bonded. Keywords: paramagnetic ruthenium anion, solvolysis, chloro complexes.

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