Влияние дейтерирования на фазовые переходы в (NH-=SUB=-4-=/SUB=-)-=SUB=-3-=/SUB=-VOF-=SUB=-5-=/SUB=-

The (ND4)3VOF5 crystal was grown with a high degree of deuteration (D ~ 92%). Structural and thermophysical studies have been carried out, the parameters of phase transitions have been determined. It was found that the deuteration of the ammonium cation in (NH4)3VOF5 led to a change in the chemical pressure, which was accompanied by an increase in the unit cell volume and an increase in the phase transition temperatures. The baric coefficients dTi / dp were determined and the phase T-p diagram (ND4)3VOF5 was constructed. A decrease in the temperature stability of the initial cubic phase Fm 3m in (ND4)3VOF5, as well as a wedging out of the intermediate monoclinic phase at a lower pressure as compared to (NH4)3VOF5, was found.

Download Full-text

Влияние дейтерирования на фазовые переходы в диоксотетрафториде ванадия

Физика твердого тела ◽

10.21883/ftt.2019.02.47134.230 ◽

2019 ◽

Vol 61 (2) ◽

pp. 330

Author(s):

Е.В. Богданов ◽

Е.И. Погорельцев ◽

М.В. Горев ◽

М.С. Молокеев ◽

И.Н. Флеров

Keyword(s):

Phase Diagram ◽

Phase Transitions ◽

Cell Volume ◽

Phase Stability ◽

Unit Cell Volume ◽

Structural Transformations ◽

Dielectric Studies ◽

Chemical Pressure ◽

Pressure Coefficients ◽

High Degree

AbstractThe crystals of (ND_4)_3VO_2F_4 with a high degree of deuteration (~87%) have been grown and a significant (~1.5%) increase in the unit cell volume has been detected. The decrease in the chemical pressure leads to a change in the sequence of phase transitions due to wedging-out of one of the rhombic phases observed in (NH_4)_3VO_2F_4. The thermal physical studies have been carried out and the entropies, deformations, and pressure coefficients related to structural transformations have been determined. The T – p phase diagram has been built and the pressure and temperature boundaries of crystal phase stability have been determined. The dielectric studies demonstrate a nonferroelectric nature of the phase transitions in (ND_4)_3VO_2F_4. The experimental and model entropies are compared. Based on the decrease in the entropy as a result of deuteration, a hypothesis on significant but not limited anharmonism of vibrations of ammonia tetrahedral corresponding to the disordering is proposed.

Download Full-text

Thermal, ferroelastic, and structural properties near phase transitions of organic–inorganic perovskite type [NH3(CH2)3NH3]CdBr4 crystals

RSC Advances ◽

10.1039/d1ra02045e ◽

2021 ◽

Vol 11 (29) ◽

pp. 17622-17629

Author(s):

Ae Ran Lim

Keyword(s):

Phase Transition ◽

Phase Transitions ◽

Thermal Behavior ◽

Structural Properties ◽

Structural Dynamics ◽

Transition Temperatures ◽

Inorganic Perovskite ◽

Phase Transition Temperatures ◽

Perovskite Type

We studied the thermal behavior and structural dynamics of [NH3(CH2)3NH3]CdBr4 near phase transition temperatures.

Download Full-text

Low-energy ferroelectric–paraelectric phase transitions of three-dimensional A(II)B(I)X3-type perovskite ferroelectrics: How to realize high phase transition temperatures

APL Materials ◽

10.1063/5.0035199 ◽

2021 ◽

Vol 9 (1) ◽

pp. 010704

Author(s):

Jie Bie ◽

Wei Fa ◽

Shuang Chen

Keyword(s):

Phase Transition ◽

Phase Transitions ◽

Paraelectric Phase ◽

Three Dimensional ◽

Low Energy ◽

Transition Temperatures ◽

Phase Transition Temperatures ◽

High Phase

Download Full-text

INDUCED CHANGES OF THERMOTROPIC PROPERTIES OF PHASE TRANSITIONS BETWEEN SMECTIC A MESOPHASE AND ISOTROPIC LIQUID: EFFECT OF SURFACES

Modern Physics Letters B ◽

10.1142/s0217984906010755 ◽

2006 ◽

Vol 20 (14) ◽

pp. 821-833 ◽

Cited By ~ 7

Author(s):

ARIF NESRULLAJEV ◽

ŞENER OKTIK

Keyword(s):

Thin Film ◽

Thin Films ◽

Phase Transition ◽

Phase Transitions ◽

Isotropic Liquid ◽

Smectic A ◽

Phase Transition Temperatures ◽

Smectic A Phase ◽

Induced Changes ◽

Thermotropic Properties

In this work, the effect of thin films on the thermotropic and thermo-optical properties and peculiarities of the phase transitions between the smectic A and isotropic liquid have been investigated. Peculiarities of the heterophase regions of the straight smectic A-isotropic liquid and reverse isotropic liquid-smectic A phase transitions have been studied. Change of morphologic properties of the heterophase regions, shift of the phase transition temperatures and the change of temperature widths of these heterophase regions under thin film influence have been observed.

Download Full-text

Mössbauer Studies of Fe2+ in Iron Langbeinites and other Crystals with Langbeinite Structure

Zeitschrift für Naturforschung A ◽

10.1515/zna-1998-1-206 ◽

1998 ◽

Vol 53 (1-2) ◽

pp. 27-37 ◽

Cited By ~ 1

Author(s):

M. Windhaus ◽

B. D. Mosel ◽

W. Müller-Warmuth

Keyword(s):

Phase Transition ◽

Phase Transitions ◽

High Temperature ◽

Low Temperature ◽

High Spin State ◽

Cubic Phases ◽

Debye Temperatures ◽

Phase Transition Temperatures ◽

Abrupt Changes ◽

Temperature Dependences

Abstract 57 Fe Mössbauer spectra have been measured at various temperatures between 4.2 K and 300 K for iron langbeinites A 2 Fe 2^04)3 with A = K, NH 4 , Rb, T1 and magnesium, manganese and cadmium lang-beinites doped with Fe" + . The spectra revealed several contributions whose isomer shifts and quadru-pole splittings have been obtained by fitting program routines. For the high-temperature cubic phases two crystallographically non-equivalent iron sites have been identified, characteristic of Fe2+ in the high-spin state. Abrupt changes of the quadrupole couplings indicated phase transitions; in some cases, the spectra have also revealed several sites for Fe2+ in low temperature phases. From the temperature dependences, phase transition temperatures, crystal field splittings and Debye temperatures have been derived.

Download Full-text

Phase Transition in Di-oleoylphosphatidylglycerol/Monoolein Membranes due to Interactions of Positively Charged Peptides at their Lipid Membrane-Interface

Bangladesh Journal of Scientific and Industrial Research ◽

10.3329/bjsir.v45i3.6530 ◽

1970 ◽

Vol 45 (3) ◽

pp. 219-224

Author(s):

Shah Md Masum ◽

Masahito Yamazaki

Keyword(s):

Phase Transition ◽

Phase Transitions ◽

Small Angle ◽

Lipid Membrane ◽

Cubic Phase ◽

Membrane Interface ◽

X Ray ◽

X Ray Scattering ◽

Charged Peptides ◽

Positively Charged

To elucidate the factors that induce phase transitions in biomembranes due to interactions of proteins/peptides at the lipid membrane-interface, the effects of positively charged peptides on the cubic phase (Q229) of Dioleoylphosphatidylglycerol (DOPG)/Monoolein (MO) membranes were investigated. Small angle X-ray Scattering (SAXS) results revealed that 12 mol% DOPG/88 mol % MO membranes in excess water at 25°C is body centered cubic phase of crystallographic space group Im3m (Q229). In presence of peptide LLKKK, the lattices constant of Q229 phase was gradually decreased with an increase of peptide concentration and a phase transition from cubic (Q229) to cubic (Q224) phase occurred at R=0.080; (R= molar ratio of peptide to lipid). On the other hand the designed peptide WLFLLKKK and antimicrobial peptide Magainin-2 induced lamellar phase (Lα) in the same mixture membranes. These results indicate that the interactions of the these peptides with this mixture membrane are different: LLKKK induces electrostatic attractive interactions and that of WLFLLKKKK and Magainin-2 bound with the lipid membranes induce electrostatic repulsive interaction at the membrane-interface, might be the major factor inducing different phase transitions in 12 mol% DOPG/88mol% MO mixture membranes. Key words: Antimicrobial peptide Magain-2; Dioleoylphosphatidylglycerol; Monoolein; Cubic phases; Small angle X-ray Scattering DOI: 10.3329/bjsir.v45i3.6530Bangladesh J. Sci. Ind. Res. 45(3), 219-224, 2010

Download Full-text

Liquid Crystalline Norcholesterylesters: Influence of the Axial Methylgroups on the Phase Transitions and the Cholesteric Helix

Zeitschrift für Naturforschung A ◽

10.1515/zna-1989-1116 ◽

1989 ◽

Vol 44 (11) ◽

pp. 1127-1130 ◽

Cited By ~ 29

Author(s):

H. Stegemeyer ◽

K. Siemensmeyer ◽

W. Sucrow ◽

L. Appel

Keyword(s):

Phase Transition ◽

Phase Transitions ◽

Liquid Crystalline ◽

Helical Structure ◽

Transition Temperatures ◽

Phase Transition Temperatures

Liquid crystalline norcholesteryl anisic esters were prepared in which the methylgroups 19, 21, 27, and 18 are removed successively from the cholestene skeleton. The influence of the axial methylgroups on the phase transition temperatures and the choleric helical structure has been investigated. On heating the 18.19.21.27-tetranorcholesteryl ester, at 155 °C an inversion of the helical screw sense from left to right was observed

Download Full-text

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

Journal of Materials Research ◽

10.1557/jmr.1999.0014 ◽

1999 ◽

Vol 14 (1) ◽

pp. 83-89 ◽

Cited By ~ 7

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.

Download Full-text