Preparation and Characterization of La1Sr2Nb5O10−x Specimens

1990 ◽  
Vol 209 ◽  
Author(s):  
Donald H. Galvàn ◽  
M. Avalos-Borja ◽  
L. Cota-Araiza ◽  
J. Cruz-Reyes ◽  
E. A. Early
Keyword(s):  
High Temperature ◽  
High Resolution ◽  
X Rays ◽  
High Resolution Tem ◽  
Nominal Stoichiometry

ABSTRACTRecently Ogushi et al reported a La-Sr-Nb-O compound with a superconducting temperature of about 225 K. The possibility of having superconductors with such a high temperature is certainly technologically relevant. We prepared specimens with the same nominal stoichiometry and performed characterization by SEM, high resolution TEM, Scanning Auger and X-rays.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

scholarly journals Common Phase and Structure Misidentifications in High-Resolution TEM Characterization of Perovskite Materials

2020 ◽  
Vol 6 (1) ◽  
pp. 1
Author(s):  
Yu-Hao Deng
Keyword(s):  
High Resolution ◽  
Research Field ◽  
Structure Characterization ◽  
Phase Identification ◽  
Lead Iodide ◽  
Perovskite Materials ◽  
High Resolution Tem ◽  
Methylammonium Lead Iodide ◽  
Dose Imaging

High-resolution TEM (HRTEM) is a powerful tool for structure characterization. However, methylammonium lead iodide (MAPbI3) perovskite is highly sensitive to electron beams and easily decomposes into lead iodide (PbI2). Misidentifications, such as PbI2 being incorrectly labeled as perovskite, are widely present in HRTEM characterization and would negatively affect the development of perovskite research field. Here misidentifications in MAPbI3 perovskite are summarized, classified, and corrected based on low-dose imaging and electron diffraction (ED) simulations. Corresponding crystallographic parameters of intrinsic tetragonal MAPbI3 and the confusable hexagonal PbI2 are presented unambiguously. Finally, the method of proper phase identification and some strategies to control the radiation damage in HRTEM are provided. This warning paves the way to avoid future misinterpretations in HRTEM characterization of perovskite and other electron beam-sensitive materials.

Structural Characterization of Epitaxial GMR Magnetic Multilayers and Spin Valves Grown by Sputter Deposition

2000 ◽  
Vol 614 ◽  
Author(s):  
H. Geng ◽  
R. Loloee ◽  
J.W. Heckman ◽  
J. Bass ◽  
W.P. Pratt ◽  
...  
Keyword(s):  
High Resolution ◽  
Epitaxial Growth ◽  
Magnetic Multilayers ◽  
Sputter Deposition ◽  
Dc Magnetron Sputtering ◽  
Cu Films ◽  
Electron Backscatter ◽  
High Resolution Tem ◽  
Fcc Structure

ABSTRACTEpitaxial Cu/Py/FeMn and (Cu/Co)×20 GMR magnetic multilayers were grown on single crystal (011) Nb that was deposited on (1121) Al2O3 substrates by dc magnetron sputtering. Electron backscatter patterns (EBSPs) revealed that the Cu films display two twin variants, corresponding to two stacking sequences of {111} planes in fcc. The epitaxial orientation relationship between the bcc Nb and both fcc Cu variants was the Nishiyama-Wasserman (N-W) relationship. Conventional TEM observations revealed epitaxial growth for both the Cu/Py/FeMn and (Cu/Co)×20 multilayers. High-resolution TEM confirmed epitaxial growth of close packed (011) Nb on (1120) Al2O3 substrates with [111]Nb∥[0001]Al2O3. Numerous small twins were observed in the Cu near the Cu-Nb interface of the Cu/Py/FeMn multilayer. In the Cu/Co multilayer, the growth planes of the Cu and Co were found to be {100} instead of the expected close-packed {111} planes of the fcc structure.

High-resolution TEM characterization of MOVPE-grown (111)-BP layer on hexagonal 6H (0001)-SiC

2005 ◽  
Vol 244 (1-4) ◽  
pp. 285-288 ◽  
Author(s):  
T. Udagawa ◽  
M. Odawara ◽  
G. Shimaoka
Keyword(s):  
High Resolution ◽  
Tem Characterization ◽  
High Resolution Tem

High-Resolution TEM Observation of AlN/GaN Grown on Si Substrates

2011 ◽  
Vol 110-116 ◽  
pp. 991-996
Author(s):  
Lee Siang Chuah ◽  
A. Mahyudin ◽  
Z. Hasan ◽  
C.W. Chin
Keyword(s):  
High Temperature ◽  
High Resolution ◽  
Growth Dynamics ◽  
High Energy ◽  
Ex Situ ◽  
Rf Plasma ◽  
Si Substrates ◽  
Cap Layer ◽  
High Resolution Tem ◽  
Aln Buffer

A high-quality crack-free AlN cap layer on GaN layer has been achieved using an AlN buffer layer directly grown on a silicon substrate at high temperature by radio frequency (RF) plasma-assisted molecular beam epitaxy. A two dimensional (2D) growth process guide to AlN cap layer of high grade crystal quality. The nucleation and the growth dynamics have been studied by in situ reflection high energy electron diffraction (RHEED) and ex situ by high resolution transmission electron microscopy (HR-TEM). The microstructure was investigated by energy-dispersive X-ray spectroscopy (EDX). It was disclosed that AlN is single crystalline with low defect. High densities of V-shaped pits were not detected at the interface between AlN and GaN layers. Contradictory the earlier reported V-shaped defects in nitride-based alloys; these V-shaped pits were condensed on top of the AlN layer because of H2 etching of the surface when a high temperature growth discontinuity between AlN and GaN layers.

Stresses experienced by AlN films grown on sapphire

2005 ◽  
Vol 892 ◽  
Author(s):  
Jie Bai ◽  
J. Bai ◽  
V.L. Tassev ◽  
M. Lal Nakarmi ◽  
W. Sun ◽  
...  
Keyword(s):  
High Temperature ◽  
High Resolution ◽  
Lattice Mismatch ◽  
Tem Analysis ◽  
Mocvd Growth ◽  
Compressive Stresses ◽  
Show Evidence ◽  
High Resolution Tem ◽  
Final Stress ◽  
Lower Temperature

AbstractThe evolution of stress during the MOCVD growth of AlN thin films on sapphire substrates under both low and high temperature conditions has been evaluated. The final stress state of the films is assumed to consist of the summation of stresses from three different sources: (1) the stress which arises from residual lattice mismatch between film and substrate i.e. that which persists after partial relaxation by misfit dislocation formation. The extent of relaxation is determined from High Resolution TEM analysis of the substrate/film interface; (2) the stress arising from the coalescence of the 3D islands nucleated in this high mismatch epitaxy process. This requires knowledge of the island sizes just prior to coalescence and this was provided by AFM studies of samples grown under the conditions of interest; and (3) the stress generated during post-growth cooling which arises from the differences in thermal expansion coefficient between AlN and sapphire. The final resultant stress, comprising the summation of stresses arising from these three sources, is found to be tensile in the sample grown at lower temperature and compressive in the sample grown at higher temperature. These results are in general qualitative agreement with results of TEM and High resolution X-ray diffraction (HRXRD) studies, which show evidence for tensile and compressive stresses in the low temperature and high temperature cases, respectively.

Microstructure characterization of a cobalt-oxide-doped cerium-gadolinium-oxide by analytical and high-resolution TEM

2007 ◽  
Vol 55 (8) ◽  
pp. 2907-2917 ◽  
Author(s):  
Zaoli Zhang ◽  
Wilfried Sigle ◽  
Manfred Rühle ◽  
Eva Jud ◽  
Ludwig J. Gauckler
Keyword(s):  
High Resolution ◽  
Cobalt Oxide ◽  
Gadolinium Oxide ◽  
Microstructure Characterization ◽  
High Resolution Tem ◽  
Cerium Gadolinium Oxide

EVOLUTION OF MICROSTRUCTURE AND PHASE COMPOSITION UPON ANNEALING OF LiFePO4 PREPARED BY A LOW TEMPERATURE METHOD

2011 ◽  
Vol 04 (02) ◽  
pp. 117-122 ◽  
Author(s):  
W. ZAJAC ◽  
J. MARZEC ◽  
W. MAZIARZ ◽  
A. RAKOWSKA ◽  
J. MOLENDA
Keyword(s):  
Electrical Conductivity ◽  
Phase Composition ◽  
High Resolution ◽  
Microstructural Characterization ◽  
Temperature Method ◽  
High Resolution Tem ◽  
Iron Valence ◽  
Evolution Of Microstructure ◽  
Type Crystal

The effect of annealing of nanosized LiFePO 4 powder on microstructure, phase composition, iron valence state and electrical conductivity has been studied. Careful microstructural characterization of the as-prepared powder using high resolution TEM revealed presence of {010}-type crystal planes at the surface of crystallites, which seem to be beneficial to electrochemical activity. The second part of the work is focused on explanation of presence and evolution of Fe 3+ detected in the material. Transmission and CEMS modes of Mössbauer spectroscopy together with TEM allowed for ruling out concept of amorphous layers containing Fe 3+ ions covering crystalline LiFePO 4 grains.

The Characterization of Thin Films and Layered Structures Using X-RAY Absorption and Reflection at Grazing Incidence

1984 ◽  
Vol 37 ◽  
Author(s):  
S. M. Heald ◽  
J. M. Tranquada ◽  
D. O. Welch ◽  
H. Chen
Keyword(s):  
Thin Films ◽  
Fine Structure ◽  
High Resolution ◽  
Grazing Incidence ◽  
X Rays ◽  
X Ray ◽  
Surface And Interface ◽  
Interface Structures ◽  
X Ray Absorption

AbstractX-rays at grazing incidence have a short, controllable penetration depth and are well suited as a probe of surface and interface structures. This paper examines the possibility applying grazing-incidence reflectivity and Extended X-Ray Absorption Fine Structure (EXAFS) measurements to such systems. Results are presented for an Al-Cu couple for which both high resolution reflectivity and interface EXAFS measurements are made. The latter results are the first interface specific EXAFS data to be reported. Distinct changes in both signals are observed upon annealing, demonstrating the potential of the techniques.

High-resolution TEM studies of mullite formation in metakaolinite

1986 ◽  
Vol 44 ◽  
pp. 466-467
Author(s):  
Mehmet Sarikaya ◽  
IInan A. Aksay
Keyword(s):  
High Temperature ◽  
High Resolution ◽  
Spinel Phase ◽  
Exothermic Reaction ◽  
High Strength ◽  
Mullite Formation ◽  
Subsequent Formation ◽  
High Resolution Tem ◽  
Mixed Systems ◽  
Microstructural Homogeneity

Studies on the compressive fracture strength (759 MPa at 15000°C) and the flexural strength (700MPaat 1300°C) of polycrystalline mullite (3Al2O3•2SiO2-2Al2O3•SiO2) illustrate its potential for high temperature applications. In the processing of these high strength mullites, molecularly mixed Al2O3-SiO2 precursors are used to enhance mullite formation rates and to achieve microstructural homogeneity in the submicrometer range. Reaction steps leading to the formation of mullite in molecularly mixed systems are not adequately understood. The prevailing problems center around (i) the composition of a spinel phase that forms at around a 980°C exothermic reaction, and (ii) the concurrent or subsequent formation and growth of mullite. Here, we report our high resolution TEM results on the formation of the spinel and mullite phases in a molecularly mixed precursor, metakaolinite (Al2O3•2SiO2).

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