Structural and magnetic properties on F-doped LiVO2 with two-dimensional triangular lattice

2011 ◽  
Vol 1344 ◽  
Author(s):  
Yang Li ◽  
Xiaoxiang Li ◽  
Lihua Liu ◽  
Ning Chen ◽  
Jose García ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Thermal Hysteresis ◽  
Magnetic Ordering ◽  
Lattice Parameter ◽  
Two Dimensional ◽  
Scanning Calorimetry ◽  
Heat Measurement ◽  
Dsc Measurements ◽  
First Order Phase Transition

ABSTRACTThe layered oxide LiVO2 recently has received more attention due to its interesting structural and magnetic behaviors involving the two-dimensional magnetic frustration in these systems. We synthesized a series of F-doped LiVO2 samples, and reported the F-doping effect on the structure and transition temperature Tt. The samples LiVO2-xFx (x=0, 0.1, 0.2 and 0.3) were characterized by X-ray diffraction, scanning electron microscope (SEM), differential scanning calorimetry (DSC), magnetic susceptibility and specific heat measurement. The structural analysis shows that with increasing x, the ratio of lattice parameter c/a increasing, i.e. in the a-b plane the lattice is compressed while in the c-axis direction the lattice expands. The DSC measurements show that a first-order phase transition happens at around 500 K, and the thermal hysteresis around phase transition temperature Tt increases with increasing x. Substitution of O with F ions results in a change of two dimensional characteristics and the distortion of the VO6 block in structure, which significantly influence the magnetic ordering transition temperature Tt.

Structure and Phase Transition of [(CH2OH)3CNH3]2SiF6

2003 ◽  
Vol 58 (2-3) ◽  
pp. 121-125 ◽  
Author(s):  
B. Kosturek ◽  
Z. Czapla ◽  
A. Waskowska
Keyword(s):  
Phase Transition ◽  
Optical Observations ◽  
Linear Birefringence ◽  
Temperature Phase ◽  
Scanning Calorimetry ◽  
Dsc Measurements ◽  
First Order Phase Transition ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
First Order Phase

Single crystals of (TRIS)2SiF6 were grown and characterised by X-ray analysis, differential scanning calorimetry (DSC) and optical investigations. They were bond to be trigonal, space group P3̅, with the unit cell dimensions a = 7.699(1), c = 7.818(2) Å . The SiF2-6 anions, located in large cavities formed by hydrogen bonded cations, are strongly disordered at room temperature. The DSC measurements revealed a first-order phase transition at TC ≈ 177 K with a hysteresis of 4 K. The nature of the transition was confirmed by a sharp increase of the linear birefringence below TC. Optical observations under a polarizing microscope showed a domain structure of the low temperature phase, characteristic of ferroelastic materials

Effect of Crystalline Structure and Impurity Content of C60 Thin Films on the Order/Disorder Phase Transition

2001 ◽  
Vol 675 ◽  
Author(s):  
Eugene A. Katz ◽  
David Faiman ◽  
Svetlana Shtutina ◽  
Aleksandra P. Isakina ◽  
Konstantin A. Yagotintsev
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Transition Temperature ◽  
Oxygen Content ◽  
Crystalline Structure ◽  
Impurity Content ◽  
Lattice Parameter ◽  
Disorder Phase Transition ◽  
Grain Sizes ◽  
First Order Phase Transition

ABSTRACTNear the temperature of 260 K, C60 crystal is known to undergo a first order phase transition, associated with changes in molecular rotations. The present paper reports the effect of the crystalline structure and impurity content of C60 thin films on their structural behavior near this phase transition. Polycrystalline C60 films with different grain sizes and oxygen content were obtained by varying the conditions of their vacuum deposition and post-grown exposure. Temperature-resolved X-ray diffraction in the range 300 – 15 K was used to determine the lattice parameter and its changes near the phase transition temperature. Decrease in grain sizes and increase in oxygen content of the films are found to lead to a gradual reduction in the discontinuity in lattice parameter and the transition temperature.

Bilayer stabilizing peptides and the inhibition of viral infection: antimeasles activity of carbobenzoxy-Ser-Leu-amide

1987 ◽  
Vol 7 (9) ◽  
pp. 745-749 ◽  
Author(s):  
Richard M. Epand ◽  
Thomas J. Lobl ◽  
H. E. Renis
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Measles Virus ◽  
Cytopathic Effect ◽  
Hexagonal Phase ◽  
Vero Cells ◽  
Time Parameter ◽  
Scanning Calorimetry ◽  
Hplc Retention Time

A number of carbobenzoxy-dipeptide-amides raise the bilayer to hexagonal phase transition temperature of dielaidoylphosphatidylethanolamine (stabilizes the bilayer). The potency of the peptides in stabilizing the bilayer phase is Z-Tyr-Leu-NH2>Z-Gly-Phe-NH2>Z-Ser-Leu-NH2>Z-Gly-Leu-NH2>Z-Gly-Gly-NH2. A linear correlation was found between the respective HPLC retention time parameter k′ for the peptide and the slope of the bilayer stabilization curve determined with model membranes by differential scanning calorimetry. One dipeptide, Z-Ser-Leu-NH2, reduces measles virus cytopathic effect (CPE) in Vero cells. The mechanism by which this peptide reduces the CPE is not known, although some peptides which raise the bilayer to hexagonal phase transition temperature of phospholipids inhibit membrane fusion.

scholarly journals Influence of dimensionality on phase transition in VO2 nanocrystals

2013 ◽  
Vol 45 (3) ◽  
pp. 305-311 ◽  
Author(s):  
V.A. Blagojevic ◽  
N. Obradovic ◽  
N. Cvjeticanin ◽  
D.M. Minic
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Transition Temperature ◽  
Apparent Activation Energy ◽  
Phase Transition Temperature ◽  
Bulk Material ◽  
Two Dimensional ◽  
Lower Phase ◽  
One Dimensional ◽  
Simultaneous Movement

Hydrothermally synthesized one-dimensional and two-dimensional nanocrystals of VO2 undergo phase transition around 65?C, where temperature and mechanism of phase transition are dependent on dimensionality of nanocrystals. Both nanocrystalline samples exhibit depression of phase transition temperature compared to the bulk material, the magnitude of which depends on the dimensionality of the nanocrystal. One-dimensional nanoribbons exhibit lower phase transition temperature and higher values of apparent activation energy than two-dimensional nanosheets. The phase transition exhibits as a complex process with somewhat lower value of enthalpy than the phase transition in the bulk, probably due to higher proportion of surface atoms in the nanocrystals. High values of apparent activation energy indicate that individual steps of the phase transition involve simultaneous movement of large groups of atoms, as expected for single-domain nanocrystalline materials.

Reversible phase transition of pyridinium-3-carboxylic acid perchlorate

2010 ◽  
Vol 66 (3) ◽  
pp. 387-395 ◽  
Author(s):  
Heng-Yun Ye ◽  
Li-Zhuang Chen ◽  
Ren-Gen Xiong
Keyword(s):  
Phase Transition ◽  
Carboxylic Acid ◽  
Relative Displacement ◽  
Temperature Phase ◽  
Scanning Calorimetry ◽  
Cell Parameters ◽  
Dsc Measurements ◽  
Reversible Phase Transition ◽  
Reversible Phase ◽  
Hydrogen Bonded

Pyridinium-3-carboxylic acid perchlorate was synthesized and separated as crystals. Differential scanning calorimetry (DSC) measurements show that this compound undergoes a reversible phase transition at ∼ 135 K with a wide hysteresis of 15 K. Dielectric measurements confirm the transition at ∼ 127 K. Measurement of the unit-cell parameters versus temperature shows that the values of the c axis and β angle change abruptly and remarkably at 129 (2) K, indicating that the system undergoes a first-order transition at T c = 129 K. The crystal structures determined at 103 and 298 K are all monoclinic in P21/c, showing that the phase transition is isosymmetric. The crystal contains one-dimensional hydrogen-bonded chains of the pyridinium-3-carboxylic acid cations, which are further linked to perchlorate anions by hydrogen bonds to form well separated infinite planar layers. The most distinct differences between the structures of the higher-temperature phase and the lower-temperature phase are the change of the distance between the adjacent pyridinium ring planes within the hydrogen-bonded chains and the relative displacement between the hydrogen-bonded layers. Structural analysis shows that the driving force of the transition is the reorientation of the pyridinium-3-carboxylic acid cations. The degree of order of the perchlorate anions may be a secondary order parameter.

scholarly journals Above Room Temperature Reversible Phase Transition Induces Distinct Dielectric and Nonlinear Optical Switching Response Behavior in Crown-Ether-Based Supramolecular Clathrate

Crystals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 184 ◽  
Author(s):  
Jing Jing ◽  
Fan Jiang ◽  
Yan-Li Wei ◽  
Chao Shi ◽  
Heng-Yun Ye ◽  
...  
Keyword(s):  
Phase Transition ◽  
Crown Ether ◽  
Optical Switching ◽  
Nonlinear Optical ◽  
Thermal Hysteresis ◽  
Switching Behavior ◽  
Stimuli Responsive ◽  
Scanning Calorimetry ◽  
Reversible Phase Transition ◽  
Reversible Phase

Stimuli-responsive materials with coexisting nonlinear optical (NLO) and dielectric properties are technologically important, which enable simultaneous conversion of optoelectronic properties between different states under external stimuli. By rationally screening guest cations (C6H5NF2)+ in the crown-ether inclusion system, we synthesized a crown-ether supramolecular compound [(C6H5NF2)(18-crown-6)][PF6] (1). Differential scanning calorimetry (DSC) showed that 1 undergoes a reversible phase transition above room temperatures (305 K/292 K), with a thermal hysteresis of 13 K. Temperature-dependent dielectric and NLO measurements show that the compound exhibits two distinct switching response behaviors. Structural analysis indicates that the order–disorder change of the host molecule 18-crown-6 and the guest organic cation during the phase transition induces the dielectric and NLO switching behavior of the compound.

The Influence of Gamma Radiation on the Glass Transition of Hydroxyapatite/Poly L-Lactide Composite

2007 ◽  
Vol 555 ◽  
pp. 497-502
Author(s):  
Dejan Miličević ◽  
S. Trifunović ◽  
N. Ignjatović ◽  
E. Suljovrujić
Keyword(s):  
Activation Energy ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Structural Relaxation ◽  
Absorbed Dose ◽  
Gel Permeation Chromatography ◽  
Chain Scission ◽  
Scanning Calorimetry ◽  
Dsc Measurements

Hydroxyapatite/poly L-lactide (HAp/PLLA) is a composite biomaterial which has been widely utilized for substitution and reparation of the hard bone tissue. It is well known that gamma irradiation has been successfully employed in the modification/sterilization of such porous composites and that it has advantages over other procedures. In this study, differential scanning calorimetry (DSC) measurements were made to investigate the influence of the radiation on glass transition behavior and structural relaxation, as well as to estimate the activation energy for this process. The apparent activation energy ΔH* for structural relaxation in the glass transition region was determined on the basis of the heating rate dependence of the glass transition temperature Tg. Furthermore, the results were correlated with those obtained by gel permeation chromatography (GPC). Our findings support the fact that the radiation-induced chain scission in the PLLA phase is the main reason for the decrease of the glass transition temperature and/or activation energy with the absorbed dose.

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