scholarly journals Structural and optical characterization of the crystalline phase transformation of electrospinning TiO2 nanofibres by high-temperatures annealing

2019 ◽  
Vol 65 (5 Sept-Oct) ◽  
pp. 459
Author(s):  
O. Secundino-Sánchez ◽  
J. Diaz-Reyes ◽  
J. F. Sánchez-Ramírez ◽  
And J.L. Jiménez-Pérez
Keyword(s):  
Phase Transformation ◽  
Raman Scattering ◽  
High Temperatures ◽  
Crystalline Phase ◽  
Annealing Temperature ◽  
Crystal Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Range ◽  
Wide Range

The electrospinning technique has been used to synthesize TiO2 nanofibres, which by annealing at high temperatures in a wide range achieves the crystal phase transformation of anatase to rutile passing through the anatase+rutile mixed. The investigated temperature range was 0-1000°C. The TiO2 nanofibres chemical stoichiometry and surface morphology were obtained by Scanning Electron Microscopy and Energy Dispersive Spectrometry. The nanofibres diameter was ranged from 137.0 to 115.3 nm in the annealing temperature interval of 0-1000°C. The influence of the annealing temperature on the structure and crystal phase quality of the TiO2crystal has been investigated by X-ray diffraction and Raman scattering. Clear evidence of nanofibres structural transformation from pure anatase to pure rutile structures, including the quasi-amorphous and anatase+rutile mixed phases has been confirmed by Raman scattering. By X-ray diffraction was found that the nanofibres crystalline phases present as preferential growth direction (101) for anatase and (110) for rutile. The Raman spectroscopy exhibits the anomalous behaviour for band broadening and shifting of Raman bands with increasing crystallite size that form the nanofibres. The room-temperature photoluminescence presents radiative bands whose main band redshifts, from 2.56 to 1.32 eV, as the crystalline phase transforms in the investigated annealing temperature range.

Crystalline phase transformation of colloidal cadmium sulfide nanocrystals

2017 ◽  
Vol 31 (06) ◽  
pp. 1750037
Author(s):  
M. Ghali ◽  
A. M. Eissa ◽  
M. M. Mosaad
Keyword(s):  
Phase Transformation ◽  
Optical Absorption ◽  
Crystalline Phase ◽  
Growth Conditions ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Solution Ph ◽  
X Ray ◽  
Ph Values ◽  
Transmission Electron

In this paper, we give a microscopic view concerning influence of the growth conditions on the physical properties of nanocrystals (NCs) thin films made of CdS, prepared using chemical bath deposition CBD technique. We show a crystalline phase transformation of CdS NCs from hexagonal wurtzite (W) structure to cubic zincblende (ZB) when the growth conditions change, particularly the solution pH values. This effect was confirmed using X-ray diffraction (XRD), transmission electron microscopy (TEM), optical absorption and photoluminescence (PL) measurements. The optical absorption spectra allow calculation of the bandgap value, [Formula: see text], where significant increase [Formula: see text]200 meV in the CdS bandgap when transforming from Hexagonal to Cubic phase was found.

Displacive Phase Transformation in Vanadium - Substituted Lanthanum Niobate

1983 ◽  
Vol 24 ◽  
Author(s):  
A. T. Aldred ◽  
S.-K. Chan ◽  
M. H. Grimsditch ◽  
M. V. Nevitt
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Low Temperature ◽  
Raman Scattering ◽  
Transformation Temperature ◽  
Complex Oxides ◽  
Temperature Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Order

ABSTRACTThe displacive transformations in complex oxides of the type LaNb1-xVxO4 has been studied by x-ray diffraction and Raman scattering for 0 < x < 0.3. X-ray diffraction results indicate that the transformation from the tetragonal high temperature structure (C4h6) to the monoclinic low-temperature structure (C2h6) is higher than first order and that the transformation temperature Tc is depressed significantly by V substitution. Raman scattering results show that the force constant between the nearest (Nb, V)O4 tetrahedral units behave uniquely compared to others. It softens at Tc as a function of composition and it also softens as a function of temperature as Tc is approached from above.

Raman Scattering and X-ray Diffraction Studies on Zinc(II)Bromide Solutions in Methanol and N,N-Dimethylformamide in the Temperature Range 77-333 K

1994 ◽  
Vol 49 (12) ◽  
pp. 1119-1130
Author(s):  
Toshiyuki Takamuku ◽  
Keisuke Nakamura ◽  
Mikito Ihara ◽  
Toshio Yamaguchi
Keyword(s):  
Raman Scattering ◽  
Methanol Solution ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Temperature Range ◽  
Methanol Solutions ◽  
Species Being ◽  
Bromide Solutions

Abstract The structure of zinc(II) bromo complexes in methanol and N,N-dimethylformamide (DMF) (molar ratio [solvent]/[ZnBr2] = 10, temperature range 77 -333 K) has been investigated by Raman scattering and X-ray diffraction. In the methanol solution symmetric Zn - Br vibrations (γ1) of the dibromo- and tribromozinc(II) complexes were observed at 209 and 184 cm-1, respectively. With decreasing temperature the intensity of the γ1 band decreased for the dibromo and increased for the tribromo complex. In addition, the γ1 band for the tetrabromo complex appeared in the supercooled and glassy methanol solutions. In the DMF solution only one band, assigned to both the dibromo-and tribromozinc(II) complexes, was observed. Its intensity did not change with temper­ature. The X-ray diffraction data revealed that the average number of Zn -Br interactions within the zinc (II) bromo complexes does not change with temperature while the number of nonbonding Br ··· Br interactions within the complexes increases from 1.5 at 298 K to 1.9 at 243 K for the methanol solution and from 1.3 at 298 K to 1.8 at 243 K for the DMF solution. These Raman and X-ray results have confirmed that in both methanol and DMF solutions at high temperatures the dibromo species is predominantly formed, whereas at low temperatures the tribromo complex is favored, the tetrabromo species being formed only in the supercooled and glassy methanol solutions. The temperature dependent equilibrium shifts of the zinc(II) bromo complexes in the methanol and DMF solutions are discussed together with previously reported results for the aqueous phase.

scholarly journals Zirconium tetrachloride revisited

2018 ◽  
Vol 74 (3) ◽  
pp. 307-311
Author(s):  
Rosendo Borjas Nevarez ◽  
Samundeeswari Mariappan Balasekaran ◽  
Eunja Kim ◽  
Philippe Weck ◽  
Frederic Poineau
Keyword(s):  
Phase Transformation ◽  
Single Crystal ◽  
Structural Parameters ◽  
X Ray Diffraction ◽  
Zirconium Tetrachloride ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Temperature Range ◽  
Crystallographic Study

Zirconium tetrachloride, ZrCl4, is a strategic material with wide-ranging applications. Until now, only one crystallographic study on ZrCl4has been reported [Krebs (1970).Z. Anorg. Allg. Chem.378, 263–272] and that was more than 40 years ago. The compound used for the previous determination was prepared from ZrO2and Cl2–CCl4, and single-crystal X-ray diffraction (SCXRD) studies on ZrCl4obtained from Zr metal have not yet been reported. In this context, we prepared ZrCl4from the reaction of Zr metal and Cl2gas in a sealed tube and investigated its structure at 100, 150, 200, 250, and 300 K. At 300 K, the SCXRD analysis indicates that ZrCl4crystallizes in the orthorhombic space groupPca21[a= 6.262 (9),b= 7.402 (11),c= 12.039 (17) Å, andV= 558.0 (14) Å3] and consists of infinite zigzag chains of edge-sharing ZrCl6octahedra. This chain motif is similar to that observed previously in ZrCl4, but the structural parameters and space group differ. In the temperature range 100–300 K, no phase transformation was identified, while elongation of intra-chain Zr...Zr [3.950 (1) Å at 100 K and 3.968 (5) Å at 300 K] and inter-chain Cl...Cl [3.630 (3) Å at 100 K and 3.687 (9) Å at 300 K] distances occurred.

scholarly journals Systematic Structural and Optical Characterization of TiO2 Nanofibres Synthesised by Electrospinning

2021 ◽  
Vol 12 ◽  
pp. 106-115
Author(s):  
Oscar Secundino-Sánchez ◽  
José F. Sánchez-Ramírez ◽  
Joel Diaz-Reyes
Keyword(s):  
Phase Transformation ◽  
High Temperatures ◽  
Crystalline Phase ◽  
Annealing Temperature ◽  
Band Gap Energy ◽  
Continuous Change ◽  
Electrospinning Technique ◽  
Average Grain Size ◽  
High Resolution Tem ◽  
Tem Microscopy

TiO2 nanofibres were synthesised by means of the electrospinning technique, which were annealed at high temperatures to achieve the crystalline phase transformation. The chemical stoichiometry of electrospun TiO2 nanofibres was estimated by EDS, finding that at low annealing temperatures excess of oxygen was detected and at high temperatures excess of titanium that originates oxygen vacancies. TEM images show clearly the formation of TiO2 nanofibres that exhibit a homogeneous and continuous aspect without the presence of crystalline defects, whose surface morphology depends strongly on the annealing temperature. The crystalline phase transformation was studied by Raman spectroscopy, which revealed that annealed TiO2 nanofibres showed a crystalline phase transformation from pure anatase to, first a mix of anatase-rutile, then pure rutile as the annealing temperature increased, which was corroborated by X-ray diffraction and high-resolution TEM microscopy. The average grain size, inside the nanofibres, increased with the crystalline phase transformation from 10 to 24 nm for anatase-TiO2 and from 30 to 47 nm for rutile-TiO2, estimated by using the Scherrer-Debye equation. The band gap energy (Eg), obtained from optical absorption spectra, decreases monotonically, where a local minimum is observed at 700 °C, which is ranged in 3.75  Eg  2.42 eV, caused by the anatase → rutile crystalline phase transformation. The photoluminescence shows that radiative bands present a gradual red-shift as the annealing temperature increases due to the continuous change of Eg.

Study on the Structure and Phase Transition of Sm Substituted BiFeO3 Nanoparticles

2011 ◽  
Vol 418-420 ◽  
pp. 278-281
Author(s):  
Yu Xia Sun ◽  
Xing Wen Zhang ◽  
Hong Ri Liu
Keyword(s):  
Phase Transition ◽  
Phase Transformation ◽  
Annealing Temperature ◽  
Raw Materials ◽  
Structural Phase ◽  
Phase Transformation Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bifeo3 Nanoparticles ◽  
Substitution Ratio

Pure and Sm substituted BiFeO3 nanoparticles were prepared by a coprecipitate method using Bi(NO3)3•5H2O and Fe(NO3)•9H2O as raw materials. X-ray diffraction pattern indicates that perovskite structural BiFeO3 can be obtained using 0.02 molar precursor precipitate by annealing at 550 °C. A structural phase transition deduced by Sm substitution was observed. SEM results showed that the size of BiFeO3 increases with annealing temperature and substitution ratio. DTA results showed that the phase transformation temperature decreases with Sm substitution ratio.

INSULATING 211 PHASE-SUPERCONDUCTING 123 PHASE TRANSFORMATION IN THE YBaCuO SYSTEM

1991 ◽  
Vol 05 (17) ◽  
pp. 1139-1145
Author(s):  
C. Y. HUANG ◽  
B. H. LOO ◽  
M. K. WU
Keyword(s):  
Phase Transformation ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Raman Scattering ◽  
Electrical Resistance ◽  
Magnetic Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electrical Resistance Measurements ◽  
Scanning Electron

We have studied the conversion of insulating Y 2 BaCuO 5 to superconducting YBa 2 Cu 3 O x by means of Raman scattering, magnetization and electrical resistance measurements, scanning electron microscope and X-ray diffraction methods. The magnetic data show that as high as 12% of the conversion can be achieved.

NICKEL SILICIDATION ON POLYCRYSTALLINE SILICON GERMANIUM FILMS

2002 ◽  
Vol 16 (28n29) ◽  
pp. 4323-4326
Author(s):  
W. K. CHOI ◽  
K. L. PEY ◽  
H. B. ZHAO ◽  
T. OSIPOWICZ ◽  
Z. X. SHEN
Keyword(s):  
Silicon Germanium ◽  
Polycrystalline Silicon ◽  
Annealing Temperature ◽  
Boundary Diffusion ◽  
Formation Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Range ◽  
Annealing Temperatures ◽  
High Annealing

The interfacial reactions of Ni with polycrystalline Si 0.8 Ge 0.2 films at a temperature range of 300-900°C by rapid thermal annealing for 60s are studied. The sheet resistances of the silicide films were relatively low at ~10 ohm/sq for samples annealed below 600°C. X-Ray diffraction results suggested the existence of low resistivity phase Ni(Si 1-x Ge x ) in the film. The significant increase in sheet resistance for films annealed at 700-900°C is probably due to the reduction in the density of Ni(Si 1-x Ge x ) as a result of fast Ni diffusion at high annealing temperatures. Fast grain boundary diffusion of Ni was suggested to cause the lowering of formation temperature of Ni(Si 1-x Ge x ) on polycrystalline Si 1-x Ge x films. Rutherford backscattering results showed that for films annealed at a temperature range of 300-600°C, Ni has reacted with the polycrystalline films. However, at an annealing temperature higher than 700°C, Ni diffused through the whole film.

scholarly journals Systematic Structural and Optical Characterization of TiO2 Nanofibers Synthesised by Electrospinning

2021 ◽  
Vol 15 ◽  
pp. 1497-1505
Author(s):  
Oscar Secundino-Sánchez ◽  
José F. Sánchez-Ramírez ◽  
Joel Diaz -Reyes
Keyword(s):  
Phase Transformation ◽  
High Temperatures ◽  
Crystalline Phase ◽  
Annealing Temperature ◽  
Band Gap Energy ◽  
Continuous Change ◽  
Electrospinning Technique ◽  
Tio2 Nanofibers ◽  
Average Grain Size ◽  
High Resolution Tem

TiO2 nanofibers were synthesised by means of the electrospinning technique, which were annealed at high temperatures to achieve the crystalline phase transformation. The chemical stoichiometry of electrospun TiO2 nanofibers was estimated by EDS, finding that at low annealing temperatures excess of oxygen was detected and at high temperatures excess of titanium that originates oxygen vacancies. TEM images show clearly the formation of TiO2 nanofibers (NF’s) that exhibit a homogeneous and continuous aspect without the presence of crystalline defects, whose surface morphology depends strongly on the annealing temperature. The crystalline phase transformation was studied by Raman spectroscopy, which revealed that annealed TiO2 NF’s showed a crystalline phase transformation from pure anatase to, first a mix of anatase-rutile, then pure rutile as the annealing temperature increased, which was corroborated by X-ray diffraction and high-resolution TEM diffraction. The average grain size, inside the NF´s, increased with the crystalline phase transformation from 10 to 24 nm for anatase-TiO2 and from 30 to 47 nm for rutile-TiO2, estimated by using the Scherrer-Debye equation. The band gap energy (Eg), obtained from optical absorption spectra, decreases monotonically, where a local minimum is observed at 700 °C ranged in 3.75 ≤ Eg ≤ 2.42 eV, caused by the anatase → rutile crystalline phase transformation. The photoluminescence shows that radiative bands show a gradual red-shift as the temperature increases due to the continuous change of Eg.

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