scholarly journals Raman Spectra of Diphenylalanine Microtubes: Polarisation and Temperature Effects

Crystals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 224 ◽  
Author(s):  
Alexander Krylov ◽  
Svetlana Krylova ◽  
Svitlana Kopyl ◽  
Aleksandr Krylov ◽  
Ferid Salehli ◽  
...  
Keyword(s):  
Phase Transition ◽  
Physical Properties ◽  
Raman Spectra ◽  
Temperature Effects ◽  
Structural Phase ◽  
Water Molecules ◽  
Temperature Dependent ◽  
Temperature Behaviour ◽  
Anomalous Temperature ◽  
Temperature Changes

Diphenylalanine microtubes have remarkable physical properties that allow one to use them in electronics. In this work, we measured polarised temperature-dependent Raman spectra in self-assembled diphenylalanine microtubes grown from the solution. We observed the anomalous temperature behaviour of the Raman lines. Their temperature changes were minimal, which required a significant improvement in the resolution and stability of Raman measurements. The anomalies in the behaviour of the spectra at about 178 K, 235 K, 255 K, 278 K, 296 K, 398 K and 412 K were observed. The structural phase transition at 398 K is irreversible. This transition is associated with the release of water molecules from nanochannels. The irreversible phase transition has a temperature range of about 10 K.

Nanodomain Size Distribution in Relaxor Ferroelectrics Determined from Temperature Dependent Raman Scattering

2006 ◽  
Vol 966 ◽  
Author(s):  
Sanju Gupta
Keyword(s):  
Phase Transition ◽  
Solid Solution ◽  
Raman Spectroscopy ◽  
Raman Scattering ◽  
Size Distribution ◽  
Raman Spectra ◽  
Structural Phase ◽  
Relaxor Ferroelectrics ◽  
Temperature Dependent ◽  
Polarization Mechanism

ABSTRACTRelaxors (PZN, in particular) is an important class of self-assembled nanostructure composite ferroelectric oxides (or perovskite) materials. The interesting features associated with the nanoregions/nanodomains required to describe these relaxors give rise to the most relevant device related characteristics and peculiar physical properties in these materials. In addition, they possess astronomical property coefficients by themselves or when modified with lead titanate (PT) forming solid solution. In the past, we conducted temperature dependent Raman scattering studies on solid solution (1−x)PZN−xPT relaxors single crystals with varying composition; x = 0.02, 0.085, and 0.11. These studies were performed to obtain relevant information about lattice/phonon dynamics for matching the application criteria such as electromechanical actuators. We showed that the sharp structural phase transition occurs at or near 460 K which is a first-order transition by fitting two spectroscopic variables in Raman spectra for one of the representative bands occurring at 277 cm−1. Besides structural phase transition, polarization mechanism for the unpoled (x = 0.02) and poled (x = 0.05) specimens is also investigated to understand the polarization mechanism in relaxors using Raman spectroscopy. The difference in the case of poled specimen is accounted for by the influence of residual electric field. Poling also suggested an enhanced local ordering and the increase in the volume of the polar nano-regions. In the present report, we attempted to determine the nanopolar region size and distribution using the above mentioned temperature dependent Raman spectra. We discuss the most suitable mathematical form of nanodomain size distribution for such inhomogeneous material is log-normal and it is bimodal depending upon the temperature regime in addition to composition. These studies helped to determine the size distribution of nanoscopic embodiments in relaxor ferroelectrics using Raman spectroscopy as a function of temperature which is a dynamical phenomenon.

scholarly journals Manifestation of magnetoelastic interactions in Raman spectra of HoxNd1−xFe3(BO3)4 crystals

2018 ◽  
Vol 08 (02) ◽  
pp. 1850011 ◽  
Author(s):  
A. S. Krylov ◽  
S. N. Sofronova ◽  
I. A. Gudim ◽  
S. N. Krylova ◽  
Rajesh Kumar ◽  
...  
Keyword(s):  
Phase Transition ◽  
Raman Spectra ◽  
Structural Phase Transition ◽  
Solid Solutions ◽  
Order Parameter ◽  
Soft Mode ◽  
Magnetic Phase ◽  
Structural Phase ◽  
Exchange Interactions ◽  
Magnetoelastic Interaction

Raman spectra of Ho[Formula: see text]NdxFe(BO3)4 ([Formula: see text], 0.75, 0.5, 0.25) have been studied in temperature range 10–400[Formula: see text]K. Two compositions ([Formula: see text], [Formula: see text]) demonstrate structural phase transition with soft mode restoration. The addition of Nd atoms increases interatomic spacing and decreases the temperature of structural phase transition. The solid solutions ([Formula: see text], 0.5, 0.25) demonstrate the emergence of the peaks corresponding to magnetoelastic interaction below Néel temperature. The order parameter of the magnetic phase transition has been determined. The equal concentrations of holmium and neodymium atoms prevent magnon soft modes condensation caused by exchange interactions in Fe–O–Fe chains are observed. Calculations confirm the data obtained in the experiment.

Phase Transitions and Water Dynamics of [Mn(H2O)6](ClO4 )2 Studied by Differential Scanning Calorimetry and Neutron Scattering Methods

2000 ◽  
Vol 55 (9-10) ◽  
pp. 759-764 ◽  
Author(s):  
E. Mikuli ◽  
A. Migdał-Mikuli ◽  
I. Natkaniec ◽  
J. Mayer
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Neutron Scattering ◽  
Structural Phase Transition ◽  
Room Temperature ◽  
Structural Phase ◽  
Water Dynamics ◽  
Water Molecules ◽  
Temperature Phase ◽  
Solid Phases

Abstract DSC measurements performed at 95 -290 K have shown that [Mn(H 2 O) 6 ](CIO 4) 2 possesses, besides a high-temperature phase, existing above 323 K, four low-temperature solid phases. The inelastic incoherent neutron scattering (IINS) spectra and neutron powder diffraction (NPD) pat-terns registered at 20 -290 K have supported the DSC results and provided evidence that the investigated substance possesses even more than five solid phases. The IINS spectra have shown that in the room-temperature phase, water molecules perform fast stochastic reorientation at the picosecond scale. The orientational disorder characteristic for the room-temperature phase can be easily overcooled and frozen. Even by relatively slow cooling at ca. 40 K/hour a metastable, orientational (protonic) glass phase is formed below ca. 160 K. Below ca. 100 K, a structural phase transition was observed by the NPD, however the IINS spectra indicate existence of the pure ordered low-temperature phase only after annealing the sample for a few hours at 100 K. On heating, a structural phase transition takes place at ca. 120 K, and at ca. 225 K water molecules begin fast reorientation.

The structural phase transition process of free-standing monoclinic vanadium dioxide micron-sized rods: temperature-dependent Raman study

RSC Advances ◽  
2015 ◽  
Vol 5 (101) ◽  
pp. 83139-83143 ◽  
Author(s):  
Huafang Zhang ◽  
Quanjun Li ◽  
Pengfei Shen ◽  
Qing Dong ◽  
Bo Liu ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Vanadium Dioxide ◽  
Structural Phase ◽  
Transition Process ◽  
Temperature Dependent ◽  
Free Standing ◽  
Lower Phase ◽  
Phase Transition Process ◽  
Raman Study

Micro-sized rods show a lower phase transition temperature than nano-sized rods, and this is interpreted on the basis of nucleating defects.

Study of Raman spectra and structural phase transition in the system Ba2Bi4−xLaxTi5O18

1996 ◽  
Vol 218 (1-2) ◽  
pp. 91 ◽  
Author(s):  
Jianjun Liu ◽  
Chunxiao Gao ◽  
Guangtian Zou ◽  
Yanrong Jin
Keyword(s):  
Phase Transition ◽  
Raman Spectra ◽  
Structural Phase Transition ◽  
Structural Phase

STRUCTURAL, TRANSPORT AND MAGNETOTRANSPORT IN NONMAGNETIC Al3+ DOPED MIXED VALENT La0.7Ca0.3Mn1-XAlXO3 MANGANITES

2012 ◽  
Vol 26 (24) ◽  
pp. 1250136 ◽  
Author(s):  
JALSHIKHABA S. RATHOD ◽  
UMA KHACHAR ◽  
R. R. DOSHI ◽  
P. S. SOLANKI ◽  
D. G. KUBERKAR
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Structural Phase ◽  
Concentration Field ◽  
Structural Disorder ◽  
Orthorhombic Structure ◽  
Temperature Dependent ◽  
Metal Insulator ◽  
Ceramic Method ◽  
Xrd Studies

We report the modifications in the transport and magnetotransport in La 0.7 Ca 0.3 Mn 1-x Al x O 3 (LCMAO); x = 0.0, 0.02, 0.04, 0.06, 0.08 and 0.1 polycrystalline manganites synthesized by conventional ceramic method. XRD studies reveal the single phasic orthorhombic structure for all the Al -doped LCMO samples without any detectable impurities and structural phase transition. SEM micrographs show island-like grain growth in all the samples studied. Transport measurements indicate an increase in resistivity and decrease in metal-insulator (M-I) transition temperature (TP) with the increase in Al -concentration. Field and temperature dependent variation in MR for all the Al (x) doped LCMO samples has been discussed in detail in the light of substitution induced structural disorder.

Dielectric properties of (NH4)2SO4 crystals in the range of electronic excitations

2009 ◽  
Vol 16 (2) ◽  
pp. 260-263 ◽  
Author(s):  
B. Andriyevsky ◽  
C. Cobet ◽  
A. Patryn ◽  
N. Esser
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Dielectric Properties ◽  
Large Temperature ◽  
Electronic Excitations ◽  
Temperature Dependent ◽  
Temperature Changes ◽  
The Real ◽  
Temperature Dependences ◽  
Simultaneous Decrease

Spectra of the real and imaginary parts of the pseudo-dielectric permittivity, 〈∊1〉(E) and 〈∊2〉(E), of ferroelectric ammonium sulfate crystals, (NH4)2SO4, have been measured in the range of electronic excitations 4.0 to 9.5 eV by ellipsometry using synchrotron radiation. Temperature dependences of the corresponding susceptibilities, 〈χ1〉(T) and 〈χ2〉(T), obtained for the photon energy E = 8.5 eV, related to excitations of oxygen p-electrons, reveal sharp peak-like temperature changes near the Curie point T C = 223 K. The large temperature-dependent increase of the imaginary part of the susceptibility χ2(T), together with a simultaneous decrease of the real part of the susceptibility χ1(T), take place at the phase transition. These anomalies have been ascribed mainly to the SO4 group of the crystal structure.

scholarly journals Фазовая диаграмма и особенности поведения мягких мод в твердых растворах со структурой хантита TbFe-=SUB=-3-x-=/SUB=-Ga-=SUB=-x-=/SUB=-(BO_3)-=SUB=-4-=/SUB=-

2022 ◽  
Vol 130 (1) ◽  
pp. 84
Author(s):  
А.С. Крылов ◽  
А.Н. Втюрин ◽  
И.А. Гудим ◽  
И.В. Немцев ◽  
С.Н. Крылова
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Phase Transitions ◽  
Raman Spectra ◽  
Solid Solutions ◽  
Structural Phase ◽  
Temperature Phase ◽  
Structural Phase Transitions ◽  
Soft Modes ◽  
Temperature Phase Diagram

The Raman spectra of four crystals of TbFe3-хGax (BO3) 4 solid solutions (x from 0 to 0.54) were studied in the temperature range from 8 to 350 K. The temperatures of structural phase transitions were determined. The observed spectral behavior is characteristic to condensation and restoration of soft modes. Soft modes are associated with a structural phase transition from the R32 phase to the P3121 phase. The Compositions-Temperature phase diagram was constructed

From structural phase transition to highly sensitive lifetime based luminescent thermometer: multifaceted modification of thermometric performance in Y0.9-xNdxYb0.1PO4 nanocrystals

2021 ◽  
Author(s):  
Kamila Maciejewska ◽  
Marcin Szalkowski ◽  
Artur Bednarkiewicz ◽  
Lukasz Marciniak
Keyword(s):  
Phase Transition ◽  
Structural Properties ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Deep Understanding ◽  
Luminescent Properties ◽  
Host Material ◽  
Temperature Dependent ◽  
Highly Sensitive

The development of highly sensitive luminescent thermometer requires deep understanding of the correlation between structural properties of the host material with temperature-dependent luminescent properties of lanthanide emitters embedded in these...

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