PREPARATION AND HOMOGENEITY OF LANTHANIDE-DOPED CERIA NANOCRYSTAL DISPERSIONS

2000 ◽  
Vol 14 (03) ◽  
pp. 79-88 ◽  
Author(s):  
A. HARTRIDGE ◽  
A. K. BHATTACHARYA
Keyword(s):  
High Resolution ◽  
Anion Vacancy ◽  
Dark Field ◽  
Correlation Spectroscopy ◽  
Inorganic Materials ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
Large Area ◽  
X Ray ◽  
Crystallite Sizes

Aqueous sols of solid solutions of the general formula Ce 1-x Ln x O 2-x/2□x/2 (Ln=entire lanthanide range, x = 0–0.50 and =anion vacancy) were synthesized using inorganic materials. The sols contained single-phase nanocrystals with particle sizes between 7–20 nm from photon correlation spectroscopy and crystallite sizes around 5 nm from X-ray diffraction. The nanocrystals were dispersed on an amorphous silica support and individual crystals examined for composition and structure by high-resolution TEM/EDAX. High-resolution pictures showed the nanocrystals to be between 4–6 nm in size, in agreement with X-ray diffraction results. Conical dark field and bright field pictures of the same area highlighted nanocrystals to be analyzed and microdiffraction of these crystals showed spot patterns of various individual planes of the fcc fluorite lattice giving lattice parameters, depending on dopant, between 5.6–5.9 Å. EDAX analysis of individual crystals compared closely to each other, to that of an average over a large area and to that of the nominal composition.

scholarly journals Dark-field electron holography as a recording of crystal diffraction in real space: a comparative study with high-resolution X-ray diffraction for strain analysis of MOSFETs

2020 ◽  
Vol 53 (4) ◽  
pp. 885-895
Author(s):  
Victor Boureau ◽  
Aurèle Durand ◽  
Patrice Gergaud ◽  
Delphine Le Cunff ◽  
Matthew Wormington ◽  
...  
Keyword(s):  
High Resolution ◽  
Field Effect Transistors ◽  
Dark Field ◽  
Oxide Semiconductor ◽  
Electron Holography ◽  
X Ray Diffraction ◽  
X Ray ◽  
Field Electron ◽  
Transmission Electron ◽  
Dark Field Electron

Diffraction-based techniques, with either electrons or photons, are commonly used in materials science to measure elastic strain in crystalline specimens. In this paper, the focus is on two advanced techniques capable of accessing strain information at the nanoscale: high-resolution X-ray diffraction (HRXRD) and the transmission electron microscopy technique of dark-field electron holography (DFEH). Both experimentally record an image formed by a diffracted beam: a map of the intensity in the vicinity of a Bragg reflection spot in the former, and an interference pattern in the latter. The theory that governs these experiments will be described in a unified framework. The role of the geometric phase, which encodes the displacement field of a set of atomic planes in the resulting diffracted beam, is emphasized. A detailed comparison of experimental results acquired at a synchrotron and with a state-of-the-art transmission electron microscope is presented for the same test structure: an array of dummy metal–oxide–semiconductor field-effect transistors (MOSFETs) from the 22 nm technology node. Both techniques give access to accurate strain information. Experiment, theory and modelling allow the illustration of the similarities and inherent differences between the HRXRD and DFEH techniques.

scholarly journals Morphology Manipulation and Related Properties of High Crystalline Bi2S3 Nanorods by Reflux Approach

2018 ◽  
Vol 4 (5) ◽  
pp. 524-526
Author(s):  
J. Arumugam ◽  
A. Dhayal Raj ◽  
A. Albert Irudayaraj
Keyword(s):  
High Resolution ◽  
Critical Role ◽  
Precursor Concentration ◽  
X Ray Diffraction ◽  
X Ray ◽  
Increase With Increase ◽  
Crystallite Sizes ◽  
Ftir Spectrometer ◽  
Diffraction Patterns ◽  
Transmission Microscope

One dimensional Bi2S3 nanorods have been successfully synthesized by a very simple reflux method with different precursor concentration for 2 hours at 180 �C. The as-synthesized Bi2S3 powders were characterized by X-ray diffraction (XRD), high resolution scanning electron microscope (HRSEM), high resolution transmission microscope (HRTEM), UV-Vis spectrometer, Fourier transform infrared (FTIR) spectrometer. X-ray diffraction (XRD) results show that the resulting nanocrystals have an orthorhombic structure. X-ray diffraction patterns indicate a polycrystalline nature and the crystallite sizes seem increase with increase in the concentration. The HRSEM and HRTEM images reveal that the diameter of the nanorods increase with increasing concentration of the precursor. Morphological analysis reveals that the as-prepared Bi2S3 nanorods can be tuned to morphology by varying precursor concentration from 0.01 M to 0.001 M. The bismuth nitrate, which is known to be a linear polymer, plays a critical role as a precursor and a template for the growth of uniform Bi2S3 nanorods. Bi2S3 nanorods are good absorbents of solar radiation and hence can be used in solar cells.

A High Resolution Study of G.P. Zones in Aluminum - 4.2 at % Silver

1982 ◽  
Vol 40 ◽  
pp. 722-723 ◽  
Author(s):  
R. Gronsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Computer Simulations ◽  
Structural Characteristics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Resolution Study

The phenomenon of clustering in Al-Ag alloys has been extensively studied since the early work of Guinierl, wherein the pre-precipitation state was characterized as an assembly of spherical, ordered, silver-rich G.P. zones. Subsequent x-ray and TEM investigations yielded results in general agreement with this model. However, serious discrepancies were later revealed by the detailed x-ray diffraction - based computer simulations of Gragg and Cohen, i.e., the silver-rich clusters were instead octahedral in shape and fully disordered, atleast below 170°C. The object of the present investigation is to examine directly the structural characteristics of G.P. zones in Al-Ag by high resolution transmission electron microscopy.

Tubulin structure at intermediate resolution

1995 ◽  
Vol 53 ◽  
pp. 852-853
Author(s):  
K. H. Downing ◽  
S. G. Wolf ◽  
E. Nogales
Keyword(s):  
High Resolution ◽  
Structural Data ◽  
Therapeutic Drug ◽  
Zinc Ions ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Negative Stain ◽  
Functional Mechanisms ◽  
Tubulin Structure

Microtubules are involved in a host of critical cell activities, many of which involve transport of organelles through the cell. Different sets of microtubules appear to form during the cell cycle for different functions. Knowledge of the structure of tubulin will be necessary in order to understand the various functional mechanisms of microtubule assemble, disassembly, and interaction with other molecules, but tubulin has so far resisted crystallization for x-ray diffraction studies. Fortuitously, in the presence of zinc ions, tubulin also forms two-dimensional, crystalline sheets that are ideally suited for study by electron microscopy. We have refined procedures for forming the sheets and preparing them for EM, and have been able to obtain high-resolution structural data that sheds light on the formation and stabilization of microtubules, and even the interaction with a therapeutic drug.Tubulin sheets had been extensively studied in negative stain, demonstrating that the same protofilament structure was formed in the sheets and microtubules. For high resolution studies, we have found that the sheets embedded in either glucose or tannin diffract to around 3 Å.

Electron Microscopy/Diffraction Study of the Ternary Mn-Er-S System

1990 ◽  
Vol 48 (1) ◽  
pp. 76-77
Author(s):  
A. R. Landa Canovas ◽  
L.C. Otero Diaz ◽  
T. White ◽  
B.G. Hyde
Keyword(s):  
Electron Microscopy ◽  
Gas Flow ◽  
Graphite Crucible ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
Alumina Crucible ◽  
X Ray ◽  
Intermediate Phases ◽  
Twin Band ◽  
Ar Gas

X-Ray diffraction revealed two intermediate phases in the system MnS+Er2S3,:MnEr2S4= MnS.Er2S3, and MnEr4S7= MnS.2Er2S3. Their structures may be described as NaCl type, chemically twinned at the unit cell level, and isostructural with CaTi2O4, and Y5S7 respectively; i.e. {l13} NaCl twin band widths are (4,4) and (4,3).The present study was to search for structurally-related (twinned B.) structures and or possible disorder, using the more sensitive and appropiate technigue of electron microscopy/diffraction.A sample with nominal composition MnEr2S4 was made by heating Mn3O4 and Er2O3 in a graphite crucible and a 5% H2S in Ar gas flow at 1500°C for 4 hours. A small amount of this material was thenannealed, in an alumina crucible, contained in sealed evacuated silica tube, for 24 days at 1100°C. Both samples were studied by X-ray powder diffraction, and in JEOL 2000 FX and 4000 EX microscopes.

Local atomic structure in tetragonal pure ZrO2nanopowders

2010 ◽  
Vol 43 (2) ◽  
pp. 227-236 ◽  
Author(s):  
Leandro M. Acuña ◽  
Diego G. Lamas ◽  
Rodolfo O. Fuentes ◽  
Ismael O. Fábregas ◽  
Márcia C. A. Fantini ◽  
...  
Keyword(s):  
Tetragonal Phase ◽  
Local Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Crystallite Sizes ◽  
Exafs Study ◽  
The Difference ◽  
X Ray Absorption ◽  
Good Agreement

The local atomic structures around the Zr atom of pure (undoped) ZrO2nanopowders with different average crystallite sizes, ranging from 7 to 40 nm, have been investigated. The nanopowders were synthesized by different wet-chemical routes, but all exhibit the high-temperature tetragonal phase stabilized at room temperature, as established by synchrotron radiation X-ray diffraction. The extended X-ray absorption fine structure (EXAFS) technique was applied to analyze the local structure around the Zr atoms. Several authors have studied this system using the EXAFS technique without obtaining a good agreement between crystallographic and EXAFS data. In this work, it is shown that the local structure of ZrO2nanopowders can be described by a model consisting of two oxygen subshells (4 + 4 atoms) with different Zr—O distances, in agreement with those independently determined by X-ray diffraction. However, the EXAFS study shows that the second oxygen subshell exhibits a Debye–Waller (DW) parameter much higher than that of the first oxygen subshell, a result that cannot be explained by the crystallographic model accepted for the tetragonal phase of zirconia-based materials. However, as proposed by other authors, the difference in the DW parameters between the two oxygen subshells around the Zr atoms can be explained by the existence of oxygen displacements perpendicular to thezdirection; these mainly affect the second oxygen subshell because of the directional character of the EXAFS DW parameter, in contradiction to the crystallographic value. It is also established that this model is similar to another model having three oxygen subshells, with a 4 + 2 + 2 distribution of atoms, with only one DW parameter for all oxygen subshells. Both models are in good agreement with the crystal structure determined by X-ray diffraction experiments.

scholarly journals Dislocation Arrangement in a Thick LEO GaN Film on Sapphire

2000 ◽  
Vol 5 (S1) ◽  
pp. 97-103
Author(s):  
Kathleen A. Dunn ◽  
Susan E. Babcock ◽  
Donald S. Stone ◽  
Richard J. Matyi ◽  
Ling Zhang ◽  
...  
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Threading Dislocations ◽  
X Ray Diffraction ◽  
Burgers Vector ◽  
X Ray ◽  
The Third ◽  
Dislocation Arrangement ◽  
Image Position ◽  
Gan Film

Diffraction-contrast TEM, focused probe electron diffraction, and high-resolution X-ray diffraction were used to characterize the dislocation arrangements in a 16µm thick coalesced GaN film grown by MOVPE LEO. As is commonly observed, the threading dislocations that are duplicated from the template above the window bend toward (0001). At the coalescence plane they bend back to lie along [0001] and thread to the surface. In addition, three other sets of dislocations were observed. The first set consists of a wall of parallel dislocations lying in the coalescence plane and nearly parallel to the substrate, with Burgers vector (b) in the (0001) plane. The second set is comprised of rectangular loops with b = 1/3 [110] (perpendicular to the coalescence boundary) which originate in the coalescence boundary and extend laterally into the film on the (100). The third set of dislocations threads laterally through the film along the [100] bar axis with 1/3<110>-type Burgers vectors These sets result in a dislocation density of ∼109 cm−2. High resolution X-ray reciprocal space maps indicate wing tilt of ∼0.5º.

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