Exceptional dielectric performance induced by the stepwise reversible phase transitions of an organic crystal: betainium chlorodifluoroacetate

2014 ◽  
Vol 2 (48) ◽  
pp. 10337-10342 ◽  
Author(s):  
Zhihua Sun ◽  
Shuquan Zhang ◽  
Chengmin Ji ◽  
Tianliang Chen ◽  
Junhua Luo
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Structural Changes ◽  
Organic Crystal ◽  
Dielectric Performance ◽  
Reversible Phase

A molecular phase transition material that exhibits exceptional dielectric performance induced by stepwise structural changes and phase transitions is reported.

Structure, ferroelasticity and Goldilocks zone phase transitions in C3H5N2Al(SO4)2·6H2O

2021 ◽  
Vol 77 (2) ◽  
pp. 225-231
Author(s):  
Bartosz Zarychta ◽  
Zbigniew Czapla ◽  
Janusz Przesławski ◽  
Przemysław Szklarz
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Structural Phase ◽  
Order Type ◽  
Optical Observations ◽  
Heating And Cooling ◽  
Reversible Phase Transition ◽  
Clear Increase ◽  
Reversible Phase ◽  
Trigonal Phase

The single crystal growth and sequence of reversible phase transition are described for C3H5N2Al(SO4)2·6H2O. Thermal and structural analyses combined with dielectric studies and optical observations revealed the structural phase transition at T 1 = 339/340 K (I↔II) and T 2 = 347/348 K (II↔III) on heating and cooling, respectively. Both phase transitions are of the first-order type. The symmetry changes from monoclinic to trigonal phase. At 293 K, the large crystals are usually divided into numerous domains of the ferroelastic type that disappear above T 1 on heating and reappear below T 1 on cooling. The domain structure pattern is characteristic for the transition between trigonal and monoclinic phases. The changes of entropy and clear increase of permittivity at T 1 provide evidence for the order–disorder character of this phase transition. The transition at T 2 seems to be displacive.

High-temperature reversible phase transitions and exceptional dielectric anomalies in cobalt(ii) based ionic crystals: [Me3NCH2X]2[CoX4] (X = Cl and Br)

2018 ◽  
Vol 47 (17) ◽  
pp. 6218-6224 ◽  
Author(s):  
Xiu-Ni Hua ◽  
Chao-Ran Huang ◽  
Ji-Xing Gao ◽  
Yang Lu ◽  
Xiao-Gang Chen ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
High Temperature ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Ionic Crystals ◽  
Temperature Phase Transition ◽  
Reversible Phase

Two isostructural cobalt(ii) based ionic crystals with exceptional dielectric anomalies have been designed as new high-temperature phase transition materials.

Phase Transition and Thermochromism of the Hybrid (C12H25NH3)2FeCl4

2006 ◽  
Vol 111 ◽  
pp. 55-58
Author(s):  
L.L. Guo ◽  
Y.D. Dai ◽  
H.X. Liu ◽  
Shi Xi Ouyang
Keyword(s):  
Phase Transition ◽  
Structural Changes ◽  
Energy Transition ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Thermal Gravimetry ◽  
Reversible Phase Transition ◽  
Rotational Motions ◽  
Xrd Patterns ◽  
Reversible Phase

This paper focuses on the structural change and the thermochromism of the phase transition of the hybrid (C12H25NH3)2FeCl4. The temperature and the structures of the phase transition is investigated by a thermal gravimetry (TG) and differential scanning calorimetry (DSC), an infrared spectra (IR) and X-ray diffraction (XRD) patterns. The UV adsorption spectra account for the thermochromism. The results suggest that the reversible phase transition arises from the structural changes of the organic chains. The thermochromism is presumably due to the electrons redistribution on the levels and to the energy transition to translational and rotational motions of the organic chains.

scholarly journals Магнитные и магнитокалорические эффекты в системах с реверсивными переходами первого рода

2021 ◽  
Vol 63 (5) ◽  
pp. 628
Author(s):  
В.И. Вальков ◽  
В.И. Каменев ◽  
А.В. Головчан ◽  
И.Ф. Грибанов ◽  
В.В. Коледов ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Structural Phase Transition ◽  
Order Phase Transition ◽  
Magnetic Order ◽  
Structural Phase ◽  
Spin Subsystem ◽  
First Order ◽  
First Order Phase ◽  
Reversible Phase

Within the framework of the model of interacting parameters of magnetic and structural orders, a theoretical analysis of magnetostructural reversible first-order phase transitions is carried out. Reversible phase transitions are characterized by a jump-like appearance of magnetic order with decreasing temperature (as in a first-order phase transition), and with a reverse increase in temperature, the magnetic order gradually disappears (as in a second-order phase transition). Such transitions are observed in some alloys of the Mn_{1-x}Cr_{x}NiGe magnetocaloric system under pressure (x = 0.11) and without (x = 0.18) and are accompanied by specific magnetic and magnetocaloric features. A phenomenological description of these features is carried out within the concept of a soft mode for the structural subsystem undergoing first-order structural phase transition (P6_{3}/mmc-P_{nma}) and the Heisenberg model for the spin subsystem. For systems with magnetostructural instability within the molecular field approximation for the spin subsystem and the shifted harmonic oscillator approximation for the lattice subsystem, it is shown that the reversible phase transitions arise when the temperature of magnetic disordering is in the temperature hysteresis region of the 1st order structural phase transition P6_{3}/mmc-P_{nma}. It is also shown that the two-peak form of the isothermal entropy, which is characteristic of reversible transitions, is due to the separation of the structural and magnetic entropy contributions.

scholarly journals Effects of Nanodomains on Local and Long-Range Phase Transitions in Perovskite-Type Eu0.8Ca0.2TiO3–δ

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 769
Author(s):  
Marc Widenmeyer ◽  
Stefano Checchia ◽  
Xingxing Xiao ◽  
Marco Scavini ◽  
Anke Weidenkaff
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Long Range ◽  
Electrical Transport ◽  
Structural Changes ◽  
Thermal Hysteresis ◽  
Local Level ◽  
Electrical Transport Properties ◽  
Distorted Octahedra ◽  
Perovskite Type

The determination of reversible phase transitions in the perovskite-type thermoelectric oxide Eu0.8Ca0.2TiO3–δ is fundamental, since structural changes largely affect the thermal and electrical transport properties. The phase transitions were characterized by heat capacity measurements, Rietveld refinements, and pair distribution function (PDF) analysis of the diffraction data to achieve information on the phase transition temperatures and order as well as structural changes on the local level and the long range. On the long-range scale, Eu0.8Ca0.2TiO3–δ showed a phase transition sequence during heating from cubic at 100 < T < 592 K to tetragonal and finally back to cubic at T > 846 K. The phase transition at T = 592 K (diffraction)/606 K (thermal analysis) was reversible with a very small thermal hysteresis of about 2 K. The local structure at 100 K was composed of a complex nanodomain arrangement of Amm2- and Pbnm-like local structures with different coherence lengths. Since in Eu0.8Ca0.2TiO3–δ the amount of Pbnm domains was too small to percolate, the competition of ferroelectrically distorted octahedra (Amm2 as in BaTiO3) and rigid, tilted octahedra (Pbnm as in CaTiO3) resulted in a cubic long-range structure at low temperatures.

Solid-state transformations in the β-form of chlorpropamide on cooling to 100 K

2011 ◽  
Vol 67 (2) ◽  
pp. 163-176 ◽  
Author(s):  
Tatiana N. Drebushchak ◽  
Valeri A. Drebushchak ◽  
Elena V. Boldyreva
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Single Crystal ◽  
Second Phase ◽  
Organic Crystals ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Reversible Phase ◽  
Alkyl Tail

A single-crystal X-ray diffraction study of the effect of cooling down to 100 K on the β-form of chlorpropamide, 4-chloro-N-(propylaminocarbonyl)benzenesulfonamide, has revealed reversible phase transitions at ∼ 257 K and between 150 and 125 K: β (Pbcn, Z′ = 1)  βII (P2/c, Z′ = 2)  βIII (P2/n, a′ = 2a, Z′ = 4); the sequence corresponds to cooling. Despite changes in the space group and number of symmetry-independent molecules, the volume per molecule changes continuously in the temperature range 100–300 K. The phase transition at ∼ 257 K is accompanied by non-merohedral twinning, which is preserved on further cooling and through the second phase transition, but the original single crystal does not crack. DSC (differential scanning calorimetry) and X-ray powder diffraction investigations confirm the phase transitions. Twinning disappears on heating as the reverse transformations take place. The second phase transition is related to a change in conformation of the alkyl tail from trans to gauche in 1/4 of the molecules, regularly distributed in the space. Possible reasons for the increase in Z′ upon cooling are discussed in comparison to other reported examples of processes (crystallization, phase transitions) in which organic crystals with Z′ > 1 have been formed. Implications for pharmaceutical applications are discussed.

scholarly journals High-Temperature-Induced Phase Transitions in Honeycomb Layered Oxides A2Ni2TeO6 (A = Na, K)

2020 ◽  
Author(s):  
Josef Rizell ◽  
Godwill Mbiti Kanyolo ◽  
Titus Masese ◽  
Yasmine Sassa ◽  
Zhen-Dong Huang
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Structural Changes ◽  
Short Communication ◽  
Hexagonal Lattice ◽  
Functional Materials ◽  
Temperature Elevation ◽  
Layered Oxides ◽  
X Ray Diffraction ◽  
X Ray

<p><b>Phase transitions have been surmised as underlying factors behind the </b><b>exceptional electrochemical, ionic and magnetic functionalities that have catapulted honeycomb layered oxides as superb functional materials. As such, in this study (<i>short communication</i>), we explore temperature elevation as an avenue for inducing phase transitions in </b><b>h</b><b>oneycomb layered oxides adopting the composition </b><b><i>A</i></b><b><sub>2</sub></b><b><i>M</i></b><b><sub>2</sub></b><b>TeO<sub>6</sub> (<i>A </i>= Li, Na, K; <i>M</i> = (transition) metal). X-ray diffraction analyses indicate structural changes occurring in Na<sub>2</sub>Ni<sub>2</sub>TeO<sub>6 </sub>hexagonal lattice (centrosymmetric <i>P</i>6<sub>3</sub>/<i>mcm </i>→ accentric <i>P</i>6<sub>3</sub>(22) space group) with increase in temperature, whilst in the potassium homologue (K<sub>2</sub>Ni<sub>2</sub>TeO<sub>6</sub>), the phase transitions entail multiple changes in the lattice (from the initial hexagonal → monoclinic (pseudo-orthorhombic) lattice at intermediate temperatures) which reverts back to its initial hexagonal lattice with further increase in temperatures. This study opens an alternative channel for generating phase transition beside electrochemical alkali (re)insertion. </b><b></b></p>

scholarly journals High-Temperature-Induced Phase Transitions in Honeycomb Layered Oxides A2Ni2TeO6 (A = Na, K)

2020 ◽  
Author(s):  
Josef Rizell ◽  
Godwill Mbiti Kanyolo ◽  
Titus Masese ◽  
Yasmine Sassa ◽  
Zhen-Dong Huang
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Structural Changes ◽  
Short Communication ◽  
Hexagonal Lattice ◽  
Functional Materials ◽  
Temperature Elevation ◽  
Layered Oxides ◽  
X Ray Diffraction ◽  
X Ray

<p><b>Phase transitions have been surmised as underlying factors behind the </b><b>exceptional electrochemical, ionic and magnetic functionalities that have catapulted honeycomb layered oxides as superb functional materials. As such, in this study (<i>short communication</i>), we explore temperature elevation as an avenue for inducing phase transitions in </b><b>h</b><b>oneycomb layered oxides adopting the composition </b><b><i>A</i></b><b><sub>2</sub></b><b><i>M</i></b><b><sub>2</sub></b><b>TeO<sub>6</sub> (<i>A </i>= Li, Na, K; <i>M</i> = (transition) metal). X-ray diffraction analyses indicate structural changes occurring in Na<sub>2</sub>Ni<sub>2</sub>TeO<sub>6 </sub>hexagonal lattice (centrosymmetric <i>P</i>6<sub>3</sub>/<i>mcm </i>→ accentric <i>P</i>6<sub>3</sub>(22) space group) with increase in temperature, whilst in the potassium homologue (K<sub>2</sub>Ni<sub>2</sub>TeO<sub>6</sub>), the phase transitions entail multiple changes in the lattice (from the initial hexagonal → monoclinic (pseudo-orthorhombic) lattice at intermediate temperatures) which reverts back to its initial hexagonal lattice with further increase in temperatures. This study opens an alternative channel for generating phase transition beside electrochemical alkali (re)insertion. </b><b></b></p>

Temperature-Dependent Solid-state Luminescence and Reversible Phase Transition of (n-Bu4N)[Au(SC6H3-3,5-Me2)2]

2003 ◽  
Vol 32 (11) ◽  
pp. 1002-1003 ◽  
Author(s):  
Seiji Watase ◽  
Takayuki Kitamura ◽  
Nobuko Kanehisa ◽  
Masami Nakamoto ◽  
Yasushi Kai ◽  
...  
Keyword(s):  
Phase Transition ◽  
Solid State ◽  
Temperature Dependent ◽  
Reversible Phase Transition ◽  
Reversible Phase ◽  
State Luminescence
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