Structural transition of VO2 (A) nanorods studied by vibrational spectroscopies

RSC Advances ◽  
2014 ◽  
Vol 4 (35) ◽  
pp. 18055-18060 ◽  
Author(s):  
Jiwei Hou ◽  
Jianwu Zhang ◽  
Zhongping Wang ◽  
Zengming Zhang ◽  
Zejun Ding
Keyword(s):  
Phase Transition ◽  
Raman Spectrum ◽  
Raman Spectra ◽  
Structural Transition ◽  
Temperature Dependent ◽  
Vibrational Spectroscopies ◽  
Increasing Temperature ◽  
Induce Phase ◽  
Induce Phase Transition

The temperature-induce phase transition of VO2 (A) nanorods was observed from the Raman spectrum. Temperature-dependent Raman spectra of the VO2 (A) during the increasing temperature.

Electronic Raman Spectra of a Low-Spin FeIII Porphyrin and Reexamination of the Vibrational Spectra of K3[Fe(CN)6] and [Fe(C5H5)2]BF4

1995 ◽  
Vol 50 (9) ◽  
pp. 881-887 ◽  
Author(s):  
Svend Sievertsen ◽  
Lutz Galich ◽  
Heiner Homborg
Keyword(s):  
Phase Transition ◽  
Raman Spectrum ◽  
Raman Spectra ◽  
Ground State ◽  
Raman Effect ◽  
Resonance Raman ◽  
Spin Orbit ◽  
Octahedral Symmetry ◽  
Molecular Electronic ◽  
Resonance Raman Spectra

The resonance Raman spectra of (nBu4N)[Fe(CN)2TPP] ((nBu4: tetra(n-butyl)ammonium; TPP: m-tetraphenylporphyrin), K3 [Fe(CN)6] and [Fe(C5H5)2]BF4 have been investigated. A molecular electronic Raman (ER) effect at 545 cm-1 is observed for (nBu4N)[Fe(CN)2TPP]. The transition occurs between lower “Γ7” and upper “Γ8” level of the spin-orbit split ground state assuming pseudo-octahedral symmetry. In contrast to earlier studies no ER effect is detected for K3[Fe(CN)6] and [Fe(C5H5)2]BF4. For Raman shifts < 800 cm-1 only one strong Raman line is observed for [Fe(C5H5)2]BF4 at 311 cm-1, assigned to the iron ring stretch designated by ν4 (a1g in D5d). Due to a phase transition of K3[Fe(CN)6], two additional strong vibrational lines at 329 and 352 cm-1 appear in the Raman spectrum taken at 10 K. Their intensities show A "term" behaviour of the resonance Raman effect with overtones and combinations for both lines. These are components of the vibronic combinations with the ν6, ν7, and ν8 modes (t1u in Oh) in the IR spectra, too.

scholarly journals First principles study on 2H–1T′ transition in MoS2 with copper

2018 ◽  
Vol 20 (42) ◽  
pp. 26986-26994 ◽  
Author(s):  
H. H. Huang ◽  
Xiaofeng Fan ◽  
David J. Singh ◽  
W. T. Zheng
Keyword(s):  
Phase Transition ◽  
First Principles ◽  
P Adsorption ◽  
First Principles Study ◽  
Induce Phase ◽  
Induce Phase Transition

Adsorption of Cu can induce phase transition of MoS2 from 2H to metallic 1T′.

Phase Transition in a Two-State Chain Interacting with a Phonon Bath

1998 ◽  
Vol 12 (14) ◽  
pp. 1485-1493 ◽  
Author(s):  
Jing Xu ◽  
Qingshan Yuan ◽  
Hong Chen
Keyword(s):  
Phase Transition ◽  
Weak Coupling ◽  
Ohmic Dissipation ◽  
Induce Phase ◽  
Induce Phase Transition

The properties of a two-state chain interacting with a phonon bath is studied in this paper. We discuss the renormalization of the single pseudospin tunneling parameter by phonons' interaction, as well as other pseudospins' correlation. We find that for Ohmic dissipation, the correlation between pseudospins vanishes and the phonons' interaction induces the localization–delocalization transition. For our discussed super-Ohmic dissipation, the phonons' interaction only reduces the tunneling parameter and does not induce phase transition. In this case the pseudospins' correlation has its effect and reduces the tunneling parameter at weak coupling. In addition, some application of our results is also discussed.

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.

Helical mesoscopic crystals based on an achiral charge-transfer complex with controllable untwisting/breaking

2021 ◽  
Vol 57 (78) ◽  
pp. 10031-10034
Author(s):  
Canglei Yang ◽  
Lixing Luo ◽  
Jinqiu Chen ◽  
Bo Yang ◽  
Wei Wang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Charge Transfer ◽  
Polar Solvent ◽  
Charge Transfer Complex ◽  
Donor And Acceptor ◽  
Induce Phase ◽  
Induce Phase Transition ◽  
Acceptor Molecules

The donor and acceptor molecules self-assemble into a helical morphology under the effect of polar solvent. By controlling the temperature to induce phase transition, the co-crystal undergoes predictable crystal breaking or untwisting.

scholarly journals Studies of an acid-induced species of purple membrane from Halobacterium halobium

1978 ◽  
Vol 171 (2) ◽  
pp. 469-476 ◽  
Author(s):  
T A Moore ◽  
M E Edgerton ◽  
G Parr ◽  
C Greenwood ◽  
R N Perham
Keyword(s):  
Phase Transition ◽  
New Species ◽  
Temperature Dependence ◽  
Ph Dependence ◽  
Low Ph ◽  
Purple Membrane ◽  
Halobacterium Halobium ◽  
Temperature Dependent ◽  
Ph Range ◽  
Increasing Temperature

A new spectral species of the purple membrane of Halobacterium halobium has been observed below pH 3.2. The formation of this new species is temperature-dependent and is favoured by increasing temperature up to the physiological range of the organism. The rate of formation at pH 3.0 and 22 degrees C is 7.9 × 10-3s-1. The spectral distribution and temperature-dependence of the new species suggest that it may be phototransiet O, stabilized by low pH. Flash-photolytic experiments in the pH range 7.2-2.7 show a pH-dependence corresponding to the static events and are consistent with a single protonation of bacteriorhodopsin below pH 3.22. These results can also be interpreted in terms of the stabilization of phototransient O at low pH. The temperature-dependence of the formation of the acid-induced species may reflect a relationship with the phase transition of the membrane.

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.

Study on Phase Stability of Hexagonal Ba(Ti0.95Fe0.05)O3-δ Ceramic via Temperature-Dependent X-Ray Diffraction

2015 ◽  
Vol 1083 ◽  
pp. 55-59
Author(s):  
Da Yong Lu ◽  
Yan Dong Wang ◽  
Shu Zhen Cui ◽  
Dan Dan Han
Keyword(s):  
Phase Transition ◽  
Curie Temperature ◽  
Phase Stability ◽  
Perovskite Structure ◽  
Oxygen Vacancies ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Defect Complexes ◽  
Increasing Temperature

The crystalline structure of the hexagonal Ba (Ti0.95Fe0.05)O3−δ(BTF) ceramic were directly measured using a temperature-dependent XRD technique. Different from the traditional structural transitions of rhombohedral-orthorhombic (−90 °C), orthorhombic-tetragonal (−10 °C), and tetragonal-cubic (i.e., the Curie temperatureTC= 130 °C) for BaTiO3, the phase transition from hexagonal to any phase above for BTF cannot occur atTCeven up to 300 °C. Increasing temperature cannot give rise to the occupation of oxygen vacancies by environmental oxygen absorbed. The lattice electro-neutrality maintained by Fe3+-VO-Fe3+defect complexes is predominant in BTF. This experiment clarifies the phase stability of the hexagonal perovskite structure aboveTCup to 300 °C.

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