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.

The structures and phase transitions in 4-aminopyridinium tetraaquabis(sulfato)iron(III), (C5H7N2)[FeIII(H2O)4(SO4)2]

2019 ◽  
Vol 75 (6) ◽  
pp. 1144-1151
Author(s):  
Tamara J. Bednarchuk ◽  
Wolfgang Hornfeck ◽  
Vasyl Kinzhybalo ◽  
Zhengyang Zhou ◽  
Michal Dušek ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Single Crystal ◽  
Room Temperature ◽  
Variable Temperature ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Hybrid Compound ◽  
Space Group ◽  
X Ray

The organic–inorganic hybrid compound 4-aminopyridinium tetraaquabis(sulfato)iron(III), (C5H7N2)[FeIII(H2O)4(SO4)2] (4apFeS), was obtained by slow evaporation of the solvent at room temperature and characterized by single-crystal X-ray diffraction in the temperature range from 290 to 80 K. Differential scanning calorimetry revealed that the title compound undergoes a sequence of three reversible phase transitions, which has been verified by variable-temperature X-ray diffraction analysis during cooling–heating cycles over the temperature ranges 290–100–290 K. In the room-temperature phase (I), space group C2/c, oxygen atoms from the closest Fe-atom environment (octahedral) were disordered over two equivalent positions around a twofold axis. Two intermediate phases (II), (III) were solved and refined as incommensurately modulated structures, employing the superspace formalism applied to single-crystal X-ray diffraction data. Both structures can be described in the (3+1)-dimensional monoclinic X2/c(α,0,γ)0s superspace group (where X is ½, ½, 0, ½) with modulation wavevectors q = (0.2943, 0, 0.5640) and q = (0.3366, 0, 0.5544) for phases (II) and (III), respectively. The completely ordered low-temperature phase (IV) was refined with the twinning model in the triclinic P{\overline 1} space group, revealing the existence of two domains. The dynamics of the disordered anionic substructure in the 4apFeS crystal seems to play an essential role in the phase transition mechanisms. The discrete organic moieties were found to be fully ordered even at room temperature.

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

Structural-phase transition in (Cu2Te)2−x(ZnTe)x at high temperature

2021 ◽  
pp. 2150113
Author(s):  
H. B. Gasimov ◽  
R. M. Rzayev
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
High Temperature ◽  
Single Crystals ◽  
Structural Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Range ◽  
Xrd Study ◽  
Xrd Method

Cu2Te single crystal was grown by the Bridgman method. X-ray diffraction (XRD) study of Cu2Te single crystals in the temperature range of 293–893 K was performed and possible phase transitions in the mentioned range of temperature have been investigated. (Cu2Te)[Formula: see text](ZnTe)[Formula: see text] single crystals also were grown with [Formula: see text], 0.05, 0.10 concentrations and structural properties of the obtained single crystals were investigated by the XRD method in the temperature range 293–893 K. Lattice parameters and possible phase transitions in the mention temperature range were determined for (Cu2Te)[Formula: see text](ZnTe)[Formula: see text] single crystals for [Formula: see text], 0.05, 0.10 concentrations.

scholarly journals Structural and optical study of the phase transitions in Lead Hafnate, PbHfO3

2014 ◽  
Vol 70 (a1) ◽  
pp. C58-C58
Author(s):  
Steven Huband ◽  
Anthony Glazer ◽  
Krystian Roleder ◽  
Andrzej Majchrowski ◽  
Pam Thomas
Keyword(s):  
Phase Transitions ◽  
Structural Phase ◽  
Orthorhombic Phase ◽  
Temperature Hysteresis ◽  
Structural Phase Transitions ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Fundamental Understanding ◽  
Distinct Temperature

Lead Hafnate undergoes two structural phase transitions as a function of temperature. The first occurs at about 1630C, consisting of a transition from an antiferroelectric orthorhombic Pbam structure [1] to another antiferroelectric orthorhombic phase with an as-yet undetermined space group. The second is to a paraelectric cubic Pm3m structure at 2090C. Dielectric spectroscopy measurements on a single crystal have shown a distinct temperature hysteresis at the orthorhombic to orthorhombic transition [2]. Recently, dielectric measurements on a ceramic sample have shown a much larger temperature hysteresis and following x-ray diffraction measurements, it is suggested that the second orthorhombic phase is in space group A2mm and undergoes another transition to a tetragonal P4mm structure before the cubic transition [3]. We report on the results of an investigation of a PbHfO3crystal using a combination of high-resolution x-ray diffraction and birefringence imaging measurements with the Metripol system. These measurements have been performed as a function of temperature from the room-temperature orthorhombic structure to the high-temperature cubic structure. The results are discussed both in the context of the published work and fundamental understanding of the origin of antiferroelectricity.

X-ray diffraction and Raman study of DL-alanine at high pressure: revision of phase transitions

2012 ◽  
Vol 68 (4) ◽  
pp. 412-423 ◽  
Author(s):  
Nikolay A. Tumanov ◽  
Elena V. Boldyreva
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Structural Phase ◽  
Group Symmetry ◽  
Second Phase ◽  
Structural Phase Transitions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Raman Study

The effect of pressure on DL-alanine has been studied by X-ray powder diffraction (up to 8.3 GPa), single-crystal X-ray diffraction and Raman spectroscopy (up to ∼ 6 GPa). No structural phase transitions have been observed. At ∼ 1.5–2 GPa, cell parameters b and c become accidentally equal to each other, but the space-group symmetry does not change. There is no phase transition between 1.7 and 2.3 GPa, contrary to what has been reported earlier [Belo et al. (2010). Vibr. Spectrosc. 54, 107–111]. The presence of the second phase transition, which was claimed to appear within the pressure range from 6.0 to 7.3 GPa (Belo et al., 2010), is also argued. The changes in the Raman spectra have been shown to be continuous in all the pressure ranges studied.

Phase transitions of (1−x) PbZrO3 + x (Na1/2Bi1/2)TiO3 (0.01 ≤ x ≤ 0.15) solid solutions

1999 ◽  
Vol 14 (1) ◽  
pp. 83-89 ◽  
Author(s):  
Jung-Kun Lee ◽  
Hyuk-Joon Youn ◽  
Kug Sun Hong
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Solid Solutions ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Phase Transition Temperatures ◽  
Temperature Phase Transition ◽  
Increasing Temperature

Morphotropic phase boundaries and temperature dependent phase transitions of (1 – x) PbZrO3 + x (Na1/2Bi1/2)TiO3 (0.01 ≤ x ≤ 0.15) solid solutions were investigated by x-ray diffraction, differential scanning calorimetry (DSC), and dielectric property analysis. Two morphotropic phase transitions at room temperature were found at x = 0.1 and 0.13, which were from antiferroelectric orthorhombic (with 4 × 4 × 2 superlattice [orthorhombic (I)]) to antiferroelectric orthorhombic (with 2 × 2 × 2 superlattice [orthorhombic (II)]) and from orthorhombic (II) to ferroelectric rhombohedral, respectively. With increasing temperature, the samples with 0.01 ≤ x < 0.1 showed two phase transitions, i.e., from orthorhombic (I) to orthorhombic (II) and from orthorhombic (II) to cubic. The other samples had only one phase transition with increasing temperature. Phase transition temperatures of all the samples were measured using DSC, and a phase diagram for the solid solutions was constructed. A model illustrating the antiparallel shift of Pb ions in the orthorhombic (II) phase was also proposed.

From six- to five-coordinated SbIII in [(CH3)3PH]3[Sb2Cl9]: transition pathways from single-crystal X-ray diffraction

2008 ◽  
Vol 64 (5) ◽  
pp. 558-566 ◽  
Author(s):  
Anna Gagor ◽  
Maciej Wojtaś ◽  
Adam Pietraszko ◽  
Ryszard Jakubas
Keyword(s):  
Phase Transitions ◽  
Phase I ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Octahedral Environment ◽  
Transition Pathways ◽  
Cl Atoms ◽  
Unusual Increase

[(CH3)3PH]3[Sb2Cl9] experiences four phase transitions which were found by means of calorimetry, thermogravimetry and X-ray diffraction. The crystal structure was solved in the space group P63/mmc at 382 K (phase I), Pnam at 295 K (phase II) and Pna21 at 175 K (phase V). We observed an unusual increase in symmetry from the monoclinic to the orthorhombic form at the IV\rightarrowV transition. The parent hexagonal high-temperature phase I consists of highly disordered [(CH3)3PH]+ cations and [Sb2Cl9]3− anions with an octahedral environment of SbIII. The transition from phases I to II is associated with the ordering of [(CH3)3PH]+ cations. Moreover, the successive transformations from phases I to V are related to the change in the arrangement of Cl atoms in [Sb2Cl9]3− anions from the discrete `face-sharing bioctahedra' (phase I) to two corner-sharing square pyramids. A mechanism for the phase transitions is proposed. It is observed that weak C—H...Cl interactions are responsible for the structure arrangement in low-temperature phases.

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