Characterization of the time-dependentL-asparagine monohydrate crystal phase transition

2011 ◽  
Vol 44 (5) ◽  
pp. 954-957 ◽  
Author(s):  
A. S. de Menezes ◽  
F. M. Ardito ◽  
A. O. dos Santos ◽  
A. J. D. Moreno ◽  
R. J. C. Lima ◽  
...  
Keyword(s):  
Phase Transition ◽  
Annealing Time ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Monoclinic System ◽  
X Ray ◽  
Temperature Phase Transition ◽  
Asparagine Monohydrate

The high-temperature phase transition of single crystals of L-asparagine monohydrate was investigated by X-ray diffraction in association with Rietveld refinement and dilatometer measurements as a function of annealing time. The X-ray results showed that, for samples annealed at 343 K (or even 333 K) for 5 h, the expected anhydrous L-asparagine phase has been formed, monoclinic system (space groupP21), with lattice parametersa= 5.0677 (2),b= 6.7657 (2),c = 8.0742 (3) Å and β = 91.276 (4)°. The results obtained from measurements as a function of annealing time confirmed that the phase transition associated with loss of the water molecule is time dependent.

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

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.

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.

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 Synthesis and Characterization of the Amidomanganates Rb2[Mn(NH2)4] and Cs2[Mn(NH2)4]

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 676
Author(s):  
Christian Bäucker ◽  
Soeren Bauch ◽  
Rainer Niewa
Keyword(s):  
High Temperature ◽  
Single Phase ◽  
Inert Atmosphere ◽  
High Temperature Phase ◽  
Synthesis And Characterization ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ir Spectroscopic

We report the successful synthesis of Rb2[Mn(NH2)4] and Cs2[Mn(NH2)4] from ammonothermal conditions at 723 K and pressures above 850 bar. Both compounds were obtained single phase according to powder X-ray diffraction. The crystal structures were determined by single crystal X-ray diffraction. For Rb2[Mn(NH2)4] we have obtained the high-temperature phase. The structures are analyzed with respect to the earlier reported alkali metal amidomanganates. Upon heating in inert atmosphere Cs2[Mn(NH2)4] decomposes to manganese nitrides. IR spectroscopic results are reported.

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–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.

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