Atomic Scale Characterization of Oxygen-Deficient Ceramic Membranes by EELS and Z-Contrast Imaging

2000 ◽  
Vol 6 (S2) ◽  
pp. 118-119
Author(s):  
Robert F. Klie ◽  
Yasuo Ito ◽  
Nigel D. Browning ◽  
Susanne Stemmer ◽  
Terry J. Mazanec
Keyword(s):  
Oxygen Vacancies ◽  
Elevated Temperatures ◽  
Equilibrium Concentration ◽  
Ceramic Membranes ◽  
Atomic Scale ◽  
Contrast Imaging ◽  
Specific Order ◽  
Scale Characterization ◽  
Temperature Equilibrium ◽  
Z Contrast

The Perovskite structured ceramic (Lax,Sr1-x)(Fey,Cr1-y)O3-δ being developed for applications in oxygen transporting membranes. The permeability of this material is limited by the number of free ions, point-defects (oxygen vacancies) and electrons in the bulk. As any ordering of these unbound particles will restrict their mobility one key issue for controlling the membrane efficiency is the formation of ordered oxygen vacancies. In particular it is very likely, that at elevated temperatures ordered micro-domains progressively grow and asymptotically reach a stable equilibrium concentration. This is consistent with the observations of Kruidhof that below a specific order-disorder transition temperature equilibrium times of 30-40 h are required to attain steady-state conditions, irrespective of the thermal history of the sample.We investigate the formation of ordered vacancies in (Lax,Sr1-x)(Fey,Cr1-y)O3-δ by atomic resolution Z-contrast imaging and electron energy-loss spectroscopy (EELS) using a 200 keV STEM/TEM JEOL2010L with a post column Gatan Image Filter (GIF).

Atomic Scale Characterization of Oxygen Vacancy Segregation at SrTiO3 Grain Boundaries

2000 ◽  
Vol 654 ◽  
Author(s):  
R.F. Klie ◽  
N. D. Browning
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Oxygen Vacancies ◽  
Elevated Temperatures ◽  
Theoretical Models ◽  
Atomic Scale ◽  
Close Proximity ◽  
Scale Characterization

AbstractWe have examined the structure, composition and bonding at an un-doped 58° [001] tilt grain-boundary in SrTiO3 in order to investigate the control that the grain boundary exerts over the bulk properties. Room temperature and in-situ heating experiments show that there is a segregation of oxygen vacancies to the grain boundary that is increased at elevated temperatures and is independent of the cation arrangement. These measurements indicate that the widely observed electronic properties of grain boundaries may be due to an excess of mobile oxygen vacancies that cause a highly doped n-type region in the close proximity ( ≍ 1 unit cell) to the boundary. These results are shown to be consistent with both theoretical models and lower resolution chemical analysis.

scholarly journals Atomic Scale Characterization of HgTe/CdTe Superlattices Using STEM Z-Contrast Imaging and VEELS

2006 ◽  
Vol 12 (S02) ◽  
pp. 518-519
Author(s):  
L Fu ◽  
N Browning ◽  
H-S Jung ◽  
C Grein
Keyword(s):  
Atomic Scale ◽  
Contrast Imaging ◽  
Scale Characterization ◽  
Z Contrast

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2006

Analysis of the Atomic Scale Oxygen Vacancy Ordering by EELS and Z-Contrast Imaging

2000 ◽  
Vol 6 (S2) ◽  
pp. 192-193
Author(s):  
Y. Ito ◽  
S. Stemmer ◽  
R.F. Klie ◽  
N.D. Browning ◽  
T.J. Mazanec
Keyword(s):  
Ceramic Membranes ◽  
Scanning Transmission Electron Microscope ◽  
Defect Chemistry ◽  
Atomic Scale ◽  
Successful Implementation ◽  
Contrast Imaging ◽  
Valence States ◽  
Scanning Transmission ◽  
Before And After ◽  
Z Contrast

Perovskite-type oxides with high electronic and ionic conductivity are very promising materials for use as dense ceramic membranes for oxygen separation. For the successful implementation of practical ceramic membranes, a full understanding of the parameters controlling the degree of non-stoichiometry, i.e. the defect chemistry is essential. A combination of Z-contrast imaging and electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) can be used to directly image crystal and defect structures and the effect of the structures on the local electronic properties (i.e. oxygen coordination and cation valence). Here the defect chemistry in SrCoO3-δ before and after a reduction treatment at high temperatures is investigated in the JEOL 201 OF STEM. This material is known to exist in a wide a variety of phases with different crystal structures, compositions and valence states of cobalt, and can be highly oxygen deficient.

Atomic Scale Analysis of Oxygen Vacancy Segregation At Grain Boundaries in Ceramic Oxides

2001 ◽  
Vol 7 (S2) ◽  
pp. 308-309
Author(s):  
N. D. Browning ◽  
J. P. Buban ◽  
Y. Ito ◽  
R. F. Klie ◽  
Y. Lei
Keyword(s):  
Grain Boundaries ◽  
Elevated Temperatures ◽  
Scanning Transmission Electron Microscope ◽  
Atomic Scale ◽  
Contrast Imaging ◽  
Ceramic Oxides ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Resolution Analysis ◽  
Z Contrast

The properties of ceramic oxides being developed for such varied applications as fuel cells, ionic transporting membranes, high-Tc superconductors, ferroelectrics and varistors are dominated by the presence of grain boundaries. Key to controlling the electronic properties of the grain boundaries in these materials is a fundamental understanding of the complex relationship between structure, composition and local electronic structure. The ability to characterize and directly correlate these parameters on the atomic scale is afforded by the combination of Z-contrast imaging and electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM). Furthermore, the recent development of in-situ heating capabilities in the JEOL 201 OF STEM/TEM permits atomic resolution analysis to be performed at elevated temperatures and the interactions of grain boundaries with the oxygen vacancies determined.Figure 1 shows an example of the type of experiment that can be performed using these methods.

Atomic Scale Analysis of a YSZ Bicrystal Grain Boundary

2001 ◽  
Vol 7 (S2) ◽  
pp. 400-401
Author(s):  
Y. Lei ◽  
Y. Ito ◽  
N. D. Browning
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Bulk Material ◽  
Atomic Scale ◽  
Structure Property ◽  
Contrast Imaging ◽  
Structure Property Relationships ◽  
Commercial Applications ◽  
Z Contrast ◽  
Electron Energy Loss

Yttria-stabilized zirconia (YSZ) has been the subject of many experimental and theoretical studies, due to the commercial applications of zirconia-based ceramics in solid state oxide fuel cells. Since the grain boundaries usually dominate the overall macroscopic performance of the bulk material, it is essential to develop a fundamental understanding of their structure-property relationships. Previous research has been performed on the atomic structure of grain boundaries in YSZ, but no precise atomic scale compositional and chemistry characterization has been carried out. Here we report a detailed analytical study of an [001] symmetric 24° bicrystal tilt grain boundary in YSZ prepared with ∼10 mol % Y2O3 by Shinkosha Co., Ltd by the combination of Z-contrast imaging and electron energy loss spectroscopy (EELS).The experimental analysis of the YSZ sample was carried out on a 200kV Schottky field emission JEOL 201 OF STEM/TEM4.

Atomic-Scale Studies of Complex Oxide Interfaces Using Aberration-Corrected Z-contrast Imaging and EELS

2006 ◽  
Vol 12 (S02) ◽  
pp. 112-113
Author(s):  
RF Klie ◽  
MA Schofield ◽  
M Varela ◽  
SJ Pennycook ◽  
A Bleloch ◽  
...  
Keyword(s):  
Complex Oxide ◽  
Atomic Scale ◽  
Contrast Imaging ◽  
Oxide Interfaces ◽  
Z Contrast ◽  
Aberration Corrected

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2006

Analysis of the Atomic Scale Defect Chemistry in Oxygen Deficient Materials by STEM

1999 ◽  
Vol 589 ◽  
Author(s):  
Y. Ito ◽  
S. Stemmer ◽  
R. F. Klie ◽  
N. D. Browning ◽  
A. Sane ◽  
...  
Keyword(s):  
Preliminary Investigation ◽  
High Mobility ◽  
Scanning Transmission Electron Microscope ◽  
Defect Chemistry ◽  
Atomic Scale ◽  
Contrast Imaging ◽  
Separation Membranes ◽  
Oxidation Reduction ◽  
Scanning Transmission ◽  
Z Contrast

AbstractThe high mobility of anion vacancies in oxygen deficient perovskite type materials makes these ceramics potential candidates for oxygen separation membranes. As a preliminary investigation of the defect chemistry in these oxides, we show here the analysis of SrCoO3−σ using atomic resolution Z-contrast imaging and electron energy loss spectroscopy in the scanning transmission electron microscope. In particular, after being subjected to oxidation/reduction cycles at high temperatures we find the formation of ordered microdomains with the brownmillerite structure.

Bonding, Defects, And Defect Dynamics In The Sic-SiO2 System

2000 ◽  
Vol 640 ◽  
Author(s):  
S. T. Pantelides ◽  
R. Buczko ◽  
M. Di Ventra ◽  
S. Wang ◽  
S.-G. Kim ◽  
...  
Keyword(s):  
First Principles ◽  
Oxidation Process ◽  
Atomic Scale ◽  
Contrast Imaging ◽  
Interface Defects ◽  
Device Applications ◽  
Z Contrast ◽  
And Control ◽  
Electron Energy Loss ◽  
Ultimate Purpose

ABSTRACTThis paper presents a review of new results obtained by a combination of first-principles theory, Z-contrast imaging, and electron-energy-loss spectroscopy in the context of a broader experimental/theoretical program to understand and control the atomic-scale structure of SiCSiO2 interfaces. The ultimate purpose is to achieve low interface trap densities for device applications. Results are given for global bonding arrangements in comparison with those of the Si-SiO2 interface, the mechanism of the oxidation process, the nature of possible interface defects and their passivation by N and H, and the formation and dissolution of C clusters in SiO2 during oxidation and reoxidation.

Understanding Metal Oxide Surfaces at the Atomic Scale: STM Investigations of Bulk-defect Dependent Surface Processes

2000 ◽  
Vol 654 ◽  
Author(s):  
Ulrike Diebold
Keyword(s):  
Oxygen Vacancies ◽  
Science Studies ◽  
Elevated Temperatures ◽  
Surface Defects ◽  
Surface Reactivity ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Oxide Surface ◽  
Tunneling Microscopy ◽  
Adsorption Sites

AbstractSurface defects are important in oxide surface chemistry, because they change not only the surface geometric structure, but also affect the local electronic structure. Scanning Tunneling Microscopy (STM) images with atomic-scale resolution, in combination with area-averaging surface spectroscopies, is an ideal tool to study local surface defects and their relationship to surface reactivity. We report STM results onTiO2(110) surfaces which show the surprising influence of bulk defects on surface properties. Thereduced crystals used in this and other surface science studies contain Ti interstitials and oxygen vacancies. Re-oxidation at elevated temperatures results in the growth of additional TiO2 layers with Ti coming from the bulk of the crystal and O from the gas phase. This often result in partially incomplete surface structures with many undercoordinated atoms. The esorption behavior of elemental S, dosed at room temperature, depends on the reduction state of the sample. This is explained by a mechanism where desorption froma weaklybound precursor state competes with the availability of new adsorption sites in the form of oxygen vacancies which migrate from the bulk to the surface.

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