scholarly journals ZnCr2O4 Inclusions in ZnO Matrix Investigated by Probe-Corrected STEM-EELS

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 888
Author(s):  
Wei Zhan ◽  
Andrey Yurievich Kosinskiy ◽  
Lasse Vines ◽  
Klaus Magnus Johansen ◽  
Patricia Almeida Carvalho ◽  
...  
Keyword(s):  
Band Gap ◽  
Chromium Oxide ◽  
Gas Sensing ◽  
Waste Water Treatment ◽  
Transmission Electron ◽  
Wide Range ◽  
Scanning Transmission ◽  
Potential Applications ◽  
Photocatalytic Material ◽  
Electron Energy Loss

The ZnCr2O4/ZnO materials system has a wide range of potential applications, for example, as a photocatalytic material for waste-water treatment and gas sensing. In this study, probe-corrected high-resolution scanning transmission electron microscopy and geometric phase analysis were utilized to study the dislocation structure and strain distribution at the interface between zinc oxide (ZnO) and embedded zinc chromium oxide (ZnCr2O4) particles. Ball-milled and dry-pressed ZnO and chromium oxide (α-Cr2O3) powder formed ZnCr2O4 inclusions in ZnO with size ~400 nm, where the interface properties depended on the interface orientation. In particular, sharp interfaces were observed for ZnO [2113]/ZnCr2O4 [110] orientations, while ZnO [1210]/ZnCr2O4 [112] orientations revealed an interface over several atomic layers, with a high density of dislocations. Further, monochromated electron energy-loss spectroscopy was employed to map the optical band gap of ZnCr2O4 nanoparticles in the ZnO matrix and their interface, where the average band gap of ZnCr2O4 nanoparticles was measured to be 3.84 ± 0.03 eV, in contrast to 3.22 ± 0.01 eV for the ZnO matrix.

Direct evidence of 2H hexagonal Si in Si nanowires

Nanoscale ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 4846-4853 ◽  
Author(s):  
Zhanbing He ◽  
Jean-Luc Maurice ◽  
Qikai Li ◽  
Didier Pribat
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
Silicon Nanowire ◽  
Chemical Vapor ◽  
Dark Field ◽  
Si Nanowires ◽  
Transmission Electron ◽  
Wide Range ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Potential Applications

Hexagonal Si (2H polytype) has attracted great interest because of its unique physical properties and wide range of potential applications. Here, through the use of atomic resolution high-angle annular dark-field scanning transmission electron microscopy, we unambiguously report the coherent intergrowth of diamond cubic (3C polytype) and 2H hexagonal Si in a silicon nanowire grown by chemical vapor deposition.

scholarly journals Unique Structural Characteristics of Catalytic Palladium/Gold Nanoparticles on Graphene

2019 ◽  
Vol 25 (1) ◽  
pp. 80-91
Author(s):  
Kavita Meduri ◽  
Candice Stauffer ◽  
Graham O'Brien Johnson ◽  
Paolo Longo ◽  
Paul G. Tratnyek ◽  
...  
Keyword(s):  
Structural Characteristics ◽  
Pd Nanoparticles ◽  
High Catalytic Activity ◽  
Clear Understanding ◽  
Material Synthesis ◽  
Transmission Electron ◽  
Strategic Approach ◽  
Wide Range ◽  
Scanning Transmission ◽  
Electron Energy Loss

AbstractAdding Au to Pd nanoparticles (NPs) can impart high catalytic activity with respect to hydrogenation of a wide range of substances. These materials are often synthesized by reducing metallic precursors; hence, sonochemical and solvothermal processes are commonly used to anchor these bimetals onto thin supports, including graphene. Although similar NPs have been studied reasonably well, a clear understanding of structural characteristics relative to their synthesis parameters is lacking, due to limitations in characterization techniques, which may prevent optimization of this very promising catalyst. In this report, a strategic approach has been used to identify this structural and material synthesis correlation, starting with controlled sample preparation and followed by detailed characterization. This includes advanced scanning transmission electron microscopy and electron energy loss spectroscopy; the latter using a state-of-the-art instrumentation to map the distribution of Pd and Au, and to identify chemical state of the Pd NPs, which has not been previously reported. Results show that catalytic bimetal NP clusters were made of small zero-valent Pd NPs aggregating to form a shell around an Au core. Not only can the described characterization approach be applied to similar material systems, but the results can guide the optimization of the synthesis procedures.

High Spatial Resolution Compositional Analysis at Interfaces

1980 ◽  
Vol 38 ◽  
pp. 356-359
Author(s):  
John B. Vander Sande ◽  
Thomas F. Kelly ◽  
Douglas Imeson
Keyword(s):  
Electron Microscope ◽  
High Spatial Resolution ◽  
Compositional Analysis ◽  
Scanning Transmission Electron Microscope ◽  
Thin Specimen ◽  
X Ray ◽  
Volume Of Interest ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Energy Loss

In the scanning transmission electron microscope (STEM) a fine probe of electrons is scanned across the thin specimen, or the probe is stationarily placed on a volume of interest, and various products of the electron-specimen interaction are then collected and used for image formation or microanalysis. The microanalysis modes usually employed in STEM include, but are not restricted to, energy dispersive X-ray analysis, electron energy loss spectroscopy, and microdiffraction.

Complex structural ordering of the oxygen deficiency in La0.5Ca2.5Mn2O7−δ Ruddlesden–Popper phases

2019 ◽  
Vol 75 (4) ◽  
pp. 644-651
Author(s):  
Daniel González-Merchante ◽  
Raquel Cortés-Gil ◽  
José M. Alonso ◽  
Emilio Matesanz ◽  
José L. Martínez ◽  
...  
Keyword(s):  
Short Range ◽  
Oxygen Deficiency ◽  
Parent Compound ◽  
Transmission Electron ◽  
Short Range Ordering ◽  
Scanning Transmission ◽  
Materials Research ◽  
Potential Applications ◽  
Complex Structural ◽  
Ferromagnetic Interactions

Ruddlesden–Popper oxides, (AO)(ABO3) n , occupy a prominent place in the landscape of materials research because of their intriguing potential applications. Compositional modifications to the cation sublattices, A or B, have been explored in order to achieve enhanced functionalities. However, changes to the anionic sublattice have been much less explored. In this work, new oxygen-deficient manganese Ruddlesden–Popper-related phases, La0.5Ca2.5Mn2O6.5 and La0.5Ca2.5Mn2O6.25, have been synthesized by controlled reduction of the fully oxidized n = 2 term La0.5Ca2.5Mn2O7. A complete structural and compositional characterization, by means of neutron diffraction, electron diffraction and atomically resolved scanning transmission electron microscopy and electron energy-loss spectroscopy techniques, allows the proposition of a topotactic reduction pathway through preferential oxygen removal in the [MnO2] layers along [031] and [0{\bar 1}3] directions. The gradual decrease of the Mn oxidation state, accommodated by short-range ordering of anionic vacancies, reasonably explains the breaking of ferromagnetic interactions reinforcing the emergence of antiferromagnetic ones. Additional short-range order–disorder phenomena of La and Ca cations have been detected in the reduced La0.5Ca2.5Mn2O7−δ, as previously reported in the parent compound.

Variation of the ELNES Under Channeling Conditions

2001 ◽  
Vol 7 (S2) ◽  
pp. 342-343
Author(s):  
S. Köstlmeier ◽  
S. Nufer ◽  
T. Gemming ◽  
M. Rühle
Keyword(s):  
Incident Beam ◽  
Scanning Transmission Electron Microscope ◽  
Orientation Dependence ◽  
Beam Direction ◽  
Rotation Axes ◽  
Transmission Electron ◽  
Anisotropic Solid ◽  
Scanning Transmission ◽  
Electron Energy Loss ◽  
Acceleration Voltage

The orientation dependence of the fine structure of the Al L1 and L2,3 electron energy loss (EELS) edges in (α-Al2O3 has been investigated by measurements with a dedicated scanning transmission electron microscope (VG HB501 STEM, 100 keV acceleration voltage). α-Al2O3 is an anisotropic solid with a complicated alternating stacking sequence of fee Al and hcp O planes along the [0001] direction [1]. This distingiushes the [0001] direction crystallographically, as the highest-order three-fold rotation axes (C3) of the trigonal crystal structure are parallel to [0001], whereas all other symmetry elements are of lower order. Group theory predicts, that more stringent symmetry selection rules apply when electronic transitions are excited by irradiation parallel to the low-index [0001] zone axis than by irradiation along any other arbitrary direction.Yet, even for a low-energy EELS edge (θE = 0.4 mrad) both scattering parallel and perpendicular to the incident beam direction are likely.

Assessment of Deformation using the Focused Ion Beam Technique

2000 ◽  
Vol 6 (S2) ◽  
pp. 530-531
Author(s):  
M.G. Burke ◽  
P.T. Duda ◽  
G. Botton ◽  
M. W. Phaneuf
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Site Specificity ◽  
Alloy 600 ◽  
The Past ◽  
Transmission Electron ◽  
Wide Range ◽  
Potential Applications ◽  
Beam Technique ◽  
Significant Attention

Focused Ion Beam (FIB) micromachining techniques have gained significant attention over the past few years as a promising method for the preparation of a variety of metallic and nonmetallic materials for subsequent characterization using transmission electron microscopy (TEM) The advantage of the FIB in terms of site specificity and speed for the preparation of uniform electron transparent sections has opened a wide range of potential applications in materials characterization. The ability to image the sample in the FIB can also provide important microstructural data for materials analysis. In this study, both conventionally electropolished and FIB-ed specimens were prepared in order to characterize the microstructure of a commercially-produced tube of Alloy 600 (approximately Ni-15 Cr-10 Fe- 0.05 C). The electropolished samples were prepared using a solution of 20% HClO4 - 80% CH3OH at ∼-40°C. The FIB sections were obtained from a cross-section of the tube that had been mechanically thinned to ∼100 μm. The section was thinned in a Micrion 2500 FIB system with a Ga ion beam at 50 kV accelerating voltage.

scholarly journals Dynamic behavior of reversible oxygen migration in irradiated-annealed high temperature superconducting wires

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yi Zhang ◽  
M. W. Rupich ◽  
Vyacheslav Solovyov ◽  
Qiang Li ◽  
Amit Goyal
Keyword(s):  
High Temperature ◽  
Annealing Treatment ◽  
Atomic Scale ◽  
Vacancy Defects ◽  
Superconducting Wires ◽  
High Temperature Superconducting ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Effect Of Oxygen ◽  
Electron Energy Loss

Abstract We use atomically resolved scanning transmission electron microscopy and electron energy loss spectroscopy to determine the atomic-scale structural, chemical and electronic properties of artificial engineered defects in irradiated-annealed high temperature superconducting wires based on epitaxial Y(Dy)BCO film. We directly probe the oxygen vacancy defects in both plane and chain sites after irradiation with 18-meV Au ions. The plane site vacancies are reoccupied during post-annealing treatment. Our results demonstrate the dynamic reversible behavior of oxygen point defects, which explains the depression and recovery of self-field critical current and critical temperature in irradiation-annealing process. These findings reveal the strong effect of oxygen vacancies in different sites on the superconductivity properties of irradiated Y(Dy)BCO film, and provide important insights into defects engineering of 2G HTS coil wires.

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