scholarly journals Revealing a masked Verwey transition in nanoparticles of coexisting Fe-oxide phases

RSC Advances ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 390-396
Author(s):  
David González-Alonso ◽  
Jesús González ◽  
Helena Gavilán ◽  
Jeppe Fock ◽  
Lunjie Zeng ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Iron Oxide ◽  
Direct Evidence ◽  
Verwey Transition ◽  
Temperature Dependent ◽  
Fe Oxide ◽  
Oxide Phases ◽  
Mixed Iron Oxide

We provide direct evidence of a Verwey transition in a nanoparticle ensemble of mixed iron-oxide phases via temperature-dependent Raman spectroscopy.

Identification of iron oxide phases in thin films grown on Al2O3(0001) by Raman spectroscopy and X-ray diffraction

2010 ◽  
Vol 604 (7-8) ◽  
pp. 679-685 ◽  
Author(s):  
Maike Lübbe ◽  
Alexander M. Gigler ◽  
Robert W. Stark ◽  
Wolfgang Moritz
Keyword(s):  
Thin Films ◽  
Raman Spectroscopy ◽  
Iron Oxide ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxide Phases

scholarly journals Raman spectroscopy to unravel the magnetic properties of iron oxide nanocrystals for bio-related applications

2019 ◽  
Vol 1 (6) ◽  
pp. 2086-2103 ◽  
Author(s):  
Martín Testa-Anta ◽  
Miguel A. Ramos-Docampo ◽  
Miguel Comesaña-Hermo ◽  
Beatriz Rivas-Murias ◽  
Verónica Salgueiriño
Keyword(s):  
Raman Spectroscopy ◽  
Magnetic Properties ◽  
Iron Oxide ◽  
Oxide Phases

Raman spectroscopy is a very valuable and fast-performance tool to gain insight first into the different iron oxide phases present in nanoparticles, to correlate then the magnetic properties with potential bio-related applications.

DIRECT EVIDENCE FOR ITINERANT MAGNETITE ABOVE AND BELOW THE VERWEY TRANSITION TEMPERATURE

2002 ◽  
Vol 09 (02) ◽  
pp. 907-912 ◽  
Author(s):  
Y. Q. CAI ◽  
K. NAKATSUJI ◽  
S. OHNO ◽  
T. IIMORI ◽  
M. YAMADA ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Synchrotron Radiation ◽  
Direct Evidence ◽  
Electronic States ◽  
Photoemission Spectroscopy ◽  
Partial Density ◽  
Verwey Transition ◽  
Temperature Dependent ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Minority Spin

The valence electronic states of Fe 3 O 4(111) films on Pt(111) were studied using temperature-dependent spin- and angle-resolved photoemission spectroscopy with synchrotron radiation. The majority- and minority-spin partial density of states (DOS) has been obtained at 300 K and 100 K, above and below the Verwey transition temperature (TV ~ 120 K ). The spectra still show substantial k-dependence at 100 K in the 3d region. This provides the most direct experimental evidence that the 3d electrons are itinerant even at T < TV.

scholarly journals Local ferroelectric polarization switching driven by nanoscale distortions in thermoelectric $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aastha Vasdev ◽  
Moinak Dutta ◽  
Shivam Mishra ◽  
Veerpal Kaur ◽  
Harleen Kaur ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Direct Evidence ◽  
Temperature Dependent ◽  
Force Microscopy ◽  
Ferroelectric Domains ◽  
Pdf Analysis ◽  
Ferroelectric Transition Temperature

AbstractA remarkable decrease in the lattice thermal conductivity and enhancement of thermoelectric figure of merit were recently observed in rock-salt cubic SnTe, when doped with germanium (Ge). Primarily, based on theoretical analysis, the decrease in lattice thermal conductivity was attributed to local ferroelectric fluctuations induced softening of the optical phonons which may strongly scatter the heat carrying acoustic phonons. Although the previous structural analysis indicated that the local ferroelectric transition temperature would be near room temperature in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te , a direct evidence of local ferroelectricity remained elusive. Here we report a direct evidence of local nanoscale ferroelectric domains and their switching in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te using piezoeresponse force microscopy(PFM) and switching spectroscopy over a range of temperatures near the room temperature. From temperature dependent (250–300 K) synchrotron X-ray pair distribution function (PDF) analysis, we show the presence of local off-centering distortion of Ge along the rhombohedral direction in global cubic $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te . The length scale of the $${\text {Ge}}^{2+}$$ Ge 2 + off-centering is 0.25–0.10 Å near the room temperatures (250–300 K). This local emphatic behaviour of cation is the cause for the observed local ferroelectric instability, thereby low lattice thermal conductivity in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te .

scholarly journals Iron Oxide-Coupled Graphite/Fe–Si Steel Structure for Analog Computing from Recycling Principle

Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 607
Author(s):  
Roberto Baca-Arroyo
Keyword(s):  
Raman Spectroscopy ◽  
Iron Oxide ◽  
Steel Structure ◽  
Oxide Thin Film ◽  
Coating Film ◽  
Analog Computing ◽  
Current Voltage ◽  
Graphite Structure ◽  
Graphite Lattice ◽  
Steel Foils

Analog computing from recycling principle for next circular economy scenario has been studied with an iron oxide-coupled graphite/Fe–Si steel structure which was built using recycled waste materials, such as lead pencil and 3% Si steel (Fe–Si steel) foils. Proximity phenomena, such as disordered structure of iron oxide and magnetostriction-induced conduction, inside graphite lattice resulted in functional properties to advance analog architectures. Thermal oxidation was the synthesis route to produce iron oxide as coating film on Fe–Si steel foil, whose structure properties were validated by Raman spectroscopy where phase formation of hematite, α-Fe2O3, resulted as iron oxide thin-film. Three graphite layers with different compositions were also analyzed by Raman spectroscopy and used for studying electrical conduction in Fe–Si steel/α-Fe2O3/graphite structure from current–voltage plots at room temperature.

On the nature of the phase transitions of aluminosilicate perrhenate sodalite

2020 ◽  
Vol 235 (6-7) ◽  
pp. 213-223
Author(s):  
Hilke Petersen ◽  
Lars Robben ◽  
Thorsten M. Gesing
Keyword(s):  
Raman Spectroscopy ◽  
Phase Transitions ◽  
Decomposition Temperature ◽  
Second Phase ◽  
Structure Property ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Two Phase ◽  
Structure Property Relationships ◽  
Heat Capacity Measurements

AbstractThe temperature-dependent structure-property relationships of the aluminosilicate perrhenate sodalite |Na8(ReO4)2|[AlSiO4]6 (ReO4-SOD) were analysed via powder X-ray diffraction (PXRD), Raman spectroscopy and heat capacity measurements. ReO4-SOD shows two phase transitions in the investigated temperature range (13 K < T < 1480 K). The first one at 218.6(1) K is correlated to the transition of dynamically ordered $P\overline{4}3n$ (> 218.6(1 K) to a statically disordered (<218.6(1) K) SOD template in $P\overline{4}3n$. The loss of the dynamics of the template anion during cooling causes an increase of disorder, indicated by an unusual intensity decrease of the 011-reflection and an increase of the Re-O2 bond length with decreasing temperature. Additionally, Raman spectroscopy shows a distortion of the ReO4 anion. Upon heating the thermal expansion of the sodalite cage originated in the tilt-mechanism causes the second phase transition at 442(1) K resulting in a symmetry-increase from $P\overline{4}3n$ to $Pm\overline{3}n$, the structure with the sodalites full framework expansion. Noteworthy is the high decomposition temperature of 1320(10) K.

Unravelling transient phases during thermal oxidation of copper for dense CuO nanowire growth

CrystEngComm ◽  
2014 ◽  
Vol 16 (16) ◽  
pp. 3264-3267 ◽  
Author(s):  
Fei Wu ◽  
Yoon Myung ◽  
Parag Banerjee
Keyword(s):  
Raman Spectroscopy ◽  
Grain Boundaries ◽  
Thermal Oxidation ◽  
High Purity ◽  
Direct Evidence ◽  
Nanowire Growth ◽  
Cupric Ion ◽  
Cuo Nanowire ◽  
Transient Phases

Direct evidence of cupric ion outdiffusion through grain boundaries during thermal oxidation of high purity Cu is obtained using Raman spectroscopy.

scholarly journals Temperature-dependent Raman spectroscopy inBaRuO3systems

2002 ◽  
Vol 65 (23) ◽  
Author(s):  
Y. S. Lee ◽  
T. W. Noh ◽  
J. H. Park ◽  
K.-B. Lee ◽  
G. Cao ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Temperature Dependent

scholarly journals Study of Thermometry in Two-Dimensional Sb2Te3 from Temperature-Dependent Raman Spectroscopy

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Manavendra P. Singh ◽  
Manab Mandal ◽  
K. Sethupathi ◽  
M. S. Ramachandra Rao ◽  
Pramoda K. Nayak
Keyword(s):  
Thermal Conductivity ◽  
Raman Spectroscopy ◽  
Temperature Coefficient ◽  
Heat Dissipation ◽  
Peak Position ◽  
Two Dimensional ◽  
Phonon Modes ◽  
Temperature Dependent ◽  
Excellent Candidate ◽  
High Figure

AbstractDiscovery of two-dimensional (2D) topological insulators (TIs) demonstrates tremendous potential in the field of thermoelectric since the last decade. Here, we have synthesized 2D TI, Sb2Te3 of various thicknesses in the range 65–400 nm using mechanical exfoliation and studied temperature coefficient in the range 100–300 K using micro-Raman spectroscopy. The temperature dependence of the peak position and line width of phonon modes have been analyzed to determine the temperature coefficient, which is found to be in the order of 10–2 cm−1/K, and it decreases with a decrease in Sb2Te3 thickness. Such low-temperature coefficient would favor to achieve a high figure of merit (ZT) and pave the way to use this material as an excellent candidate for thermoelectric materials. We have estimated the thermal conductivity of Sb2Te3 flake with the thickness of 115 nm supported on 300-nm SiO2/Si substrate which is found to be ~ 10 W/m–K. The slightly higher thermal conductivity value suggests that the supporting substrate significantly affects the heat dissipation of the Sb2Te3 flake.

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