scholarly journals Vacancy defect control of colossal thermopower in FeSb2

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Qianheng Du ◽  
Lijun Wu ◽  
Huibo Cao ◽  
Chang-Jong Kang ◽  
Christie Nelson ◽  
...  
Keyword(s):  
Phonon Scattering ◽  
Vacancy Defect ◽  
Electron Microscopic ◽  
First Principle Calculation ◽  
Conducting Path ◽  
Transmission Electron ◽  
Vacancy Ordering ◽  
Defect Control ◽  
Scanning Transmission ◽  
Monoclinic Distortion

AbstractIron diantimonide is a material with the highest known thermoelectric power. By combining scanning transmission electron microscopic study with electronic transport neutron, X-ray scattering, and first principle calculation, we identify atomic defects that control colossal thermopower magnitude and nanoprecipitate clusters with Sb vacancy ordering, which induce additional phonon scattering and substantially reduce thermal conductivity. Defects are found to cause rather weak but important monoclinic distortion of the unit cell Pnnm → Pm. The absence of Sb along [010] for high defect concentration forms conducting path due to Fe d orbital overlap. The connection between atomic defect anisotropy and colossal thermopower in FeSb2 paves the way for the understanding and tailoring of giant thermopower in related materials.

Microstructural and Chemical Characterization of Ordered Structure in Yttrium Doped Ceria

2013 ◽  
Vol 19 (1) ◽  
pp. 102-110 ◽  
Author(s):  
Pengfei Yan ◽  
Toshiyuki Mori ◽  
Yuanyuan Wu ◽  
Zhimin Li ◽  
Graeme John Auchterlonie ◽  
...  
Keyword(s):  
Chemical Characterization ◽  
Electron Microscopic Observation ◽  
Doped Ceria ◽  
Electron Microscopic ◽  
Ordered Structures ◽  
Transmission Electron ◽  
Vacancy Ordering ◽  
Crystal Model ◽  
Electron Energy Loss

AbstractThe ordered structures in different doping levels (x = 0.1, 0.15, 0.2, 0.25, 0.3) of yttrium doped ceria (YDC, Ce(1−x)YxO2−δ) electrolytes were investigated by electron diffraction, high-resolution transmission electron microscopy (TEM), scanning TEM, and electron energy loss spectroscopy. Oxygen vacancy ordering was experimentally confirmed within the ordered structures. With increasing the doping level, the concentration of trivalent Ce cations was increased in YDC samples and such trivalent Ce cations were supposed to mainly exist in the ordered structures. Based on our electron microscopic observation and microanalysis, a crystal model for the ordered structures is proposed.

scholarly journals Atomic origin of spin-valve magnetoresistance at the SrRuO3 grain boundary

2020 ◽  
Vol 7 (4) ◽  
pp. 755-762 ◽  
Author(s):  
Xujing Li ◽  
Li Yin ◽  
Zhengxun Lai ◽  
Mei Wu ◽  
Yu Sheng ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Density Functional ◽  
Magnetic Moments ◽  
Spin Valve ◽  
Density Functional Theory Calculations ◽  
Precise Knowledge ◽  
Transmission Electron ◽  
Defect Control ◽  
Scanning Transmission ◽  
Low Dimensional

Abstract Defects exist ubiquitously in crystal materials, and usually exhibit a very different nature from the bulk matrix. Hence, their presence can have significant impacts on the properties of devices. Although it is well accepted that the properties of defects are determined by their unique atomic environments, the precise knowledge of such relationships is far from clear for most oxides because of the complexity of defects and difficulties in characterization. Here, we fabricate a 36.8° SrRuO3 grain boundary of which the transport measurements show a spin-valve magnetoresistance. We identify its atomic arrangement, including oxygen, using scanning transmission electron microscopy and spectroscopy. Based on the as-obtained atomic structure, the density functional theory calculations suggest that the spin-valve magnetoresistance occurs because of dramatically reduced magnetic moments at the boundary. The ability to manipulate magnetic properties at the nanometer scale via defect control allows new strategies to design magnetic/electronic devices with low-dimensional magnetic order.

Incoherent Imaging by Z-Contrast Stem: Towards 1Å Resolution

1994 ◽  
Vol 332 ◽  
Author(s):  
S. J. Pennycook ◽  
D. E. Jesson ◽  
A. J. Mcgibbon
Keyword(s):  
Phonon Scattering ◽  
Scanning Transmission Electron Microscope ◽  
Complex Materials ◽  
Intrinsic Resolution ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Detector Geometry ◽  
Incoherent Imaging ◽  
Z Contrast ◽  
Contrast Image

ABSTRACTBy averaging phase correlations between scattered electrons a high angle detector in the scanning transmission electron microscope (STEM) can provide an incoherent, Z-contrast image at atomic resolution. Phase coherence is effectively destroyed through a combination of detector geometry (transverse incoherence) and phonon scattering (longitudinal incoherence). Besides having a higher intrinsic resolution, incoherent imaging offers the possibility of robust reconstruction to higher resolutions, provided that some lower frequency information is present in the image. This should have value for complex materials and regions of complex atomic arrangements such as grain boundaries. Direct resolution of the GaAs sublattice with a 300kV is demonstrated.

Annular Dark Field Imaging in Stem

1994 ◽  
Vol 332 ◽  
Author(s):  
Sean Hillyard ◽  
John Silcox
Keyword(s):  
Phonon Scattering ◽  
Dark Field ◽  
Probe Intensity ◽  
Dark Field Imaging ◽  
Quantitative Measurements ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Computer Based ◽  
Diffraction Patterns

ABSTRACTAnnular dark field scanning transmission electron microscopy (ADF STEM) is chemically sensitive at high spatial resolution (e.g., 1.8ë at 100keV). Images can be digitally acquired and recorded, permitting quantitative analysis. It is particularly powerful when used in combination with complementary analysis modes such as x-ray microanalysis and transmission electron energy loss spectroscopy. Critical to the interpretation of these data is an understanding and determination of the electron probe intensity, shape and propagation characteristics inside the specimen. Quantitative measurements of diffraction patterns and images in comparison with computer-based simulations (including phonon scattering) provide a basis for developing that information. Results of a series of studies are reviewed that address questions such as defocus and other instrumental factors, and also the formation of channeling peaks that appear on the atomic columns along zone axes. For example, along Si(100) a peak forms and penetrates over 500ë whereas along Ge(100) it developes rapidly but disappears in less than 200ë. In higher atomic number elements, the penetration is even less (e.g. 1 O0ë for In).

High-angle annular dark field scanning transmission electron microscopic (HAADF-STEM) study of Fe-rich 7 Å–14 Å interstratified minerals from a hydrothermal deposit

Clay Minerals ◽  
2016 ◽  
Vol 51 (4) ◽  
pp. 603-613 ◽  
Author(s):  
Sayako Inoué ◽  
Toshihiro Kogure
Keyword(s):  
Dark Field ◽  
High Angle ◽  
Electron Microscopic ◽  
Octahedral Sheet ◽  
Scanning Transmission Electron ◽  
Lateral Contact ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Hydrothermal Environments

AbstractThe distribution of octahedral cations in the two component layers of a 7 Å–14 Å interstratified mineral with a bulk chemical composition (Fe4.122+Mg0.07Mn0.01Al1.69□0.11)(Si2.56Al1.44) O10(OH)8 was investigated using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) in combination with the image simulations. In the 14 Å component layers, comparison between the observed and simulated images revealed that the M4 sites of the interlayer sheets were occupied preferentially by Al together with a small amount of Fe; the other M1, M2 and M3 sites were occupied by dominant Fe and residual Al in equal proportions. Two types of octahedral sheets with disordered and ordered cation distributions were recognized in the 7 Å component layers. The two types of sheets were similar to the octahedral sheet of the 2:1 layer and the interlayer sheet in the 14 Å layer above, respectively. Irregular vertical stacking and lateral contact of the different component layers in structure and chemistry characterized the interstratification, which may be caused by rapid precipitation and accretion of the component layers in hydrothermal environments.

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