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Delimitis, Andreas; Hansen, Vidar Folke; Symeou, Elli; Kyratsi, Theodora; Minde, Mona Wetrhus & Taftø, Johan
(2019).
DETERMINATION OF HOST AND DOPANT ION DISTRIBUTION IN MG2SI1-XSNX THERMOELECTRIC MATERIALS BY ELECTRON CHANNELING.
Acta Crystallographica Section A: Foundations and Advances.
ISSN 2053-2733.
75.
doi:
10.1107/S2053273319092350.
Vis sammendrag
Detailed structure studies by electron microscopy methods have been widely exploited due to the unique
capabilities electrons provide. Precise identification of atomic positions is feasible by employing spectroscopy
techniques in an analytical transmission electron microscope. In this aspect, methods such as energy dispersive Xray
spectroscopy (EDS) are utilised, under strong channelling conditions, where the yield of element characteristic
X-ray emission can be modified and manipulated, dependent upon crystallographic directions of the incident
beam. These channelling effects are powerful in determining atomic site locations in crystals and techniques such
as ALCHMI (Atom Location by Channeling Enhanced MIcroanalysis) have been developed and evaluated.
Structural analyses employing electron channelling have a recent focus in systems for renewable technologies and
energy harvesting, such as thermoelectric (TE) materials. TEs based on Mg2Si1-xSnx have gained increased interest,
due to inexpensive production costs, abundancy and a toxic nature of raw materials, especially for power
generation applications within the intermediate temperature range (500–900 K). Synthesis of Mg2Si1-xSnx in
nanocrystal morphologies, often coupled by incorporation of dopants in their host matrix is exploited, with a scope
to efficiently reduce thermal conductivity, particularly for Sn-rich or Bi doped Si-rich compounds. Previous studies
confirmed the multiplicity of phases in this system, however, the precise distribution of host and dopant ions
location is still controversial. Application of the electron channelling technique is therefore more than essential in
order to accurately determine and refine their structural characteristics. Experimental outcomes will be
demonstrated and discussed.
-
Delimitis, Andreas; Hansen, Vidar Folke; Symeou, Elli; Kyratsi, Theodora; Minde, Mona Wetrhus & Taftø, Johan
(2019).
Determination of host and dopant ion distribution in Mg2Si1-xSnx thermoelectric materials by electron channeling.
Vis sammendrag
Detailed structure studies by electron microscopy methods have been widely exploited due to the unique capabilities electrons provide. Precise identification of atomic positions is feasible by employing spectroscopy techniques in an analytical transmission electron microscope. In this aspect, methods such as energy dispersive X-ray spectroscopy (EDS) are utilised, under strong channeling conditions, where the yield of element characteristic X-ray emission can be modified and manipulated, dependent upon crystallographic directions of the incident beam. These channeling effects are powerful in determining atomic site locations in crystals and techniques such as ALCHEMI (Atom Location by CHanneling Enhanced MIcroanalysis) have been developed and evaluated.
Structural analyses employing electron channeling have a recent focus in systems for renewable technologies and energy harvesting, such as thermoelectric (TE) materials. TEs based on Mg2Si1-xSnx have gained increased interest, due to inexpensive production costs, abundancy and atoxic nature of raw materials, especially for power generation applications within the intermediate temperature range (500–900 K). Synthesis of Mg2Si1-xSnx in nanocrystal morphologies, often coupled by incorporation of dopants in their host matrix is exploited, with a scope to efficiently reduce thermal conductivity, particularly for Sn-rich or Bi doped Si-rich compounds. Previous studies confirmed the multiplicity of phases in this system, however, the precise distribution of host and dopant ions location is still controversial. Application of the electron channeling technique is therefore more than essential in order to accurately determine and refine their structural characteristics. Experimental outcomes will be demonstrated and discussed.
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Løvvik, Ole Martin; Song, Xin; Valset, Kjetil; Flage-Larsen, Espen; Fjeld, Harald & Graff, Joachim Seland
[Vis alle 14 forfattere av denne artikkelen]
(2014).
Thermoelectric materials from first principles to final applications: Basic and applied thermoelectrics in Oslo.
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Qureishy, Thomas; Hansen, Vidar; Karlsen, Ole Bjørn; Gunnæs, Anette Eleonora & Taftø, Johan
(2012).
Superstructures in Mg2Si1-xSnx.
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Valset, Kjetil; Prytz, Øystein; Hansen, Vidar & Taftø, Johan
(2012).
Quantitative study of structure factors at large reciprocal vectors using convergent beam electron diffraction: Application to anharmonicity of the thermal motion in Mg2Si.
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Flage-Larsen, Espen; Prytz, Øystein & Taftø, Johan
(2011).
The Lorenz function; its scattering properties and the validity of the parabolic approximation.
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Flage-Larsen, Espen; Prytz, Øystein & Taftø, Johan
(2011).
Material-specific Lorenz numbers: Electronic and lattice parts of the thermal conductivity.
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Valset, Kjetil; Böttger, Paul Heinrich Michael; Taftø, Johan & Finstad, Terje
(2011).
High mobility Cu-doped ZnSb containing particles of Zn3P2.
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Song, Xin; Karlsen, Ole Bjørn; Taftø, Johan; Böttger, Paul Heinrich Michael & Finstad, Terje
(2011).
Electrical and structural characterization of thermoelectric material ZnSb with additions of Mn and Cr.
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Song, Xin; Valset, Kjetil; Böttger, Paul Heinrich Michael; Karlsen, Ole Bjørn; Finstad, Terje & Taftø, Johan
(2011).
Structure and Thermoelectric Properties of Cr and Mn Doped ZnSb.
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Rauwel, Protima; Ole Martin, Løvvik; Rauwel, Erwan Yann; Toberer, Erik; Snyder, Jeffery & Taftø, Johan
(2010).
Nanostructuring in thermoelectric Zn4Sb3 with varying Zn concentrations.
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Prytz, Øystein; Toberer, E. S.; May, A. F.; Flage-Larsen, Espen; Snyder, G. J. & Taftø, Johan
(2010).
Transmission electron microscopy studies of nanostructures in SrZnSb2: reduced thermal conductivity through defect scattering.
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Løvvik, Ole Martin; Flage-Larsen, Espen; Rauwel, Protima; Prytz, Øystein & Taftø, Johan
(2010).
Solubility and mobility of Zn in Zn4Sb3 - a combined computational and experimental study.
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Flage-Larsen, Espen & Taftø, Johan
(2010).
Transport properties in light of analytic band generation: the potential of energy filtering and the validity of the parabolic approximation.
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Valset, Kjetil & Taftø, Johan
(2010).
Bloch wave description of refraction at interfaces.
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Böttger, Paul Heinrich Michael; Valset, Kjetil; Flage-Larsen, Espen; Prytz, Øystein; Bording, Jan Kåre & Karlsen, Ole Bjørn
[Vis alle 9 forfattere av denne artikkelen]
(2009).
An overview of our basic and applied thermoelectric research activity.
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Prytz, Øystein; Gunnæs, Anette Eleonora; Breivik, Tallak Harald; Toberer, E. S.; Snyder, G. J. & Taftø, Johan
(2009).
Nanostructured thermoelectric materials, reduction of thermal conductivity in Zn4Sb3.
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Valset, Kjetil; Böttger, Paul Heinrich Michael; Karlsen, Ole Bjørn & Taftø, Johan
(2009).
Microstructure and thermoelectric property studies of ZnSb with Sb and Zn4Sb3 inclusions.
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Bording, Jan Kåre; Prytz, Øystein; Hansen, Vidar & Taftø, Johan
(2009).
Improved thermoelectric materials through nanostructuring: implications for energy savings.
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Sæterli, Ragnhild; Flage-Larsen, Espen; Prytz, Øystein; Taftø, Johan; Marthinsen, Knut & Holmestad, Randi
(2009).
Electron energy loss near edge structure of phosphorus L2,3 edges in skutterudites.
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Prytz, Øystein; Flage-Larsen, Espen; Gu, L.; Sigle, W. & Taftø, Johan
(2009).
The charge-ordered spinel AlV2O4: EELS and DFT studies.
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Taftø, Johan
(2008).
CBED with the electron beam cross-over at and above the specimen level.
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Prytz, Øystein; Gunnæs, Anette Eleonora; Toberer, Eric; Snyder, Jeff & Taftø, Johan
(2008).
Transmission electron microscopy search for defects and disorder causing the low thermal conductivity of Zn4Sb3.
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Prytz, Øystein; Gunnæs, Anette Eleonora; Breivik, Tallak Harald; Toberer, Eric; Snyder, Jeff & Taftø, Johan
(2008).
Transmission Electron Microscopy Studies of Nanostructure in ß-Zn4Sb3.
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Flage-Larsen, Espen; Prytz, Øystein; Løvvik, Ole Martin & Taftø, Johan
(2007).
Calculation of valence electron distribution and thermoelectric coefficients in skutterudies.
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Flage-Larsen, Espen; Prytz, Øystein; Løvvik, Ole Martin; Wu, L.; Zhu, Y. & Taftø, Johan
(2007).
Bonding and valence electron distribution in thermoelectric skutterudites.
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Prytz, Øystein; Flage-Larsen, Espen; Karlsen, Ole Bjørn; Diplas, Spyridon; Finstad, Terje & Taftø, Johan
[Vis alle 11 forfattere av denne artikkelen]
(2007).
Electronic structure of thermoelectric skutterudites; combining spectroscopic techniques, precision electron diffraction and density functional theory.
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Sæterli, Ragnhild; Prytz, Øystein; Marthinsen, Knut; Holmestad, Randi & Taftø, Johan
(2007).
EELS study of phosphorus L-edges of skutterudites.
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Taftø, Johan; Prytz, Øystein; Wu, Lijun & Zhu, Yimei
(2007).
Valence electron distribution studied by electron diffraction.
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Sæterli, Ragnhild; Prytz, Øystein; Vullum, Per Erik; Taftø, Johan & Holmestad, Randi
(2007).
EELS and CBED studies of skutterudites.
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Sæterli, Ragnhild; Prytz, Øystein; Holmestad, Randi; Marthinsen, Knut & Taftø, Johan
(2007).
The local electronic structure of phosphorus in skutterudites studied by electron energy-loss spectroscopy.
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Sæterli, Ragnhild; Prytz, Øystein; Vullum, Per Erik; Marthinsen, Knut; Holmestad, Randi & Taftø, Johan
(2007).
Convergent beam electron diffraction experiments on thermoelectric skutterudites.
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Sæterli, Ragnhild; Prytz, Øystein; Vullum, Per Erik; Friis, Jesper; Marthinsen, Knut & Holmestad, Randi
[Vis alle 7 forfattere av denne artikkelen]
(2007).
Convergent beam electron diffraction experiments on thermoelectric skutterudites.
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Prytz, Øystein; Sæterli, Ragnhild; Holmestad, Randi & Taftø, Johan
(2007).
Investigations of bonding in skutterudites by electron energy loss spectroscopy.
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Sæterli, Ragnhild; Prytz, Øystein; Holmestad, Randi; Marthinsen, Knut & Taftø, Johan
(2007).
The local electronic structure of phosphorus in skutterudites studied by electron energy-loss spectroscopy.
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Prytz, Øystein; Sæterli, Ragnhild; Randi, Holmestad & Taftø, Johan
(2007).
Investigations of bonding in skutterudites by electron energy loss spectroscopy.
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Prytz, Øystein; Løvvik, Ole Martin & Taftø, Johan
(2005).
Experimental and theoretical studies of plasma resonance and the electronic structure of binary skutterudites.
Vis sammendrag
We determine the plasmon energies of the skutterudites CoP3, CoAs3 and CoSb3 by electron energy loss spectroscopy, and compare with calculated values from the Drude model and density functional theory (DFT). For these compounds, whose doped versions have potential applications as thermoelectric materials, there is a relatively large discrepancy between experiment and theory based on the Drude model as well as the DFT-calculations. We also study the transitions from occupied to unoccupied states near the Fermi-level that show up at energies lower than the plasmon energies. The features observed are in general agreement with the DFT-calculations.
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Taftø, Johan
(2004).
Quantitive electron diffraction in studies of electron distribution in crystals.
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Taftø, Johan
(2004).
Beyond locating the atoms towards addressing the electronic structure of crystals using advanced transmission electron microscopy.
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Prytz, Øystein & Taftø, Johan
(2004).
Accurate determination of orientation relationships between ferroelastic domains: the tetragonal to monoclinic transition in LaNbO4 as an example.
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LaNbO4 crystallizes in a tetragonal high-temperature phase with space group I41/a, which
transforms to a monoclinic phase upon cooling below 500 °C. The low-temperature phase has
space group I2/a (C2/c) with a monoclinic angle b=94.1°. This system serves as a useful model
of a ferroelastic transition of the 4/mF2/m type using the notation of Aizu [1]. This transition
produces ferroelastic domains, the boundaries between which are parallel to the monoclinic baxis.
The orientation of these boundaries relative to the monoclinic a- and c-axes has been
predicted by Sapriel [2] for all 94 ferroelastic species, and calculations specifically for the
LaNbO4 system have been presented by Jian and Wayman [3].
We present an accurate determination of the boundary orientation in LaNbO4 using selected
area electron diffraction. The boundary planes are parallel to the (2 0 5.10)/(5.10 0 2) planes of
the two domains, as opposed to the predictions of Jian and Wayman which indicate that the
domain boundaries should be oriented parallel to the (2 0 -4.04)/(4.04 0 2) planes. Our
experimental results are in good agreement with the results of a previous study [4].
Furthermore, we present a simple geometric model for calculating the boundary orientation
based only on the unit cell parameters of the monoclinic phase. This model gives a boundary
orientation in excellent agreement with our experimental determination.
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Jahren, Jens; Sørbrøden, Erik; Gunnæs, Anette E.; Taftø, Johan & Aagaard, Per
(2003).
SEM, STEM and EELS of Fe-hydroxide from the Langøya Gypsum Landfill.
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Zhu, Yimei; Wu, L.J.; Taftø, Johan; Schofield, M.A.; Volkov, V.V. & Beleggia, M.
[Vis alle 7 forfattere av denne artikkelen]
(2003).
Understanding spatial distribution of electrostatic and magnetic potentials in materials.
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Taftø, Johan; Klie, Robert F. & Zhu, Yimei
(2003).
Electronic structure information from EELS using the anisotropic superconductor MgB2 as an example.
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Foss, Steinar & Taftø, Johan
(2003).
Investigation of fast electrons propagating nearly parallel to interfaces.
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Jahren, Jens; Sørbrøden, Erik; Gunnæs, Anette Eleonora; Taftø, Johan & Aagaard, Per
(2003).
SEM, TEM and EELS of Fe-hydroxide from the Langøya gypsum landfill.
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Sørbrøden, Erik; Hansen, Vidar; Olsen, Arne; Holme, Børge & Taftø, Johan
(2002).
Imaging of hardening particles in an Al-Mg-Zn alloy using plasmon electron energy losses.
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Taftø, Johan
(2002).
Characteristic energy losses of channeled electrons; reciprocity and double alignment.
Vis sammendrag
Channeling of fast electrons in crystals monitored by detecting element characteristic energy losses.
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Taftø, Johan; Foss, Steinar; Olsen, Arne & Simensen, Christian J.
(2002).
Locating atoms in small crystals by combining convergent beam electron diffraction and electron channeling.
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Study of the crystal structure of microcrystals by electron channeling
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Zhu, Yimei; Wu, L.J. & Taftø, Johan
(2002).
A Challenging to Characterization of Superconductors: Accurate Measurements of Charge Distribution and Interfacial Displacement.
Vis sammendrag
Maasurements of lattice displacements with picometer accuracy by coherent electron diffraction.
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Prytz, Øystein; Taftø, Johan; Fjellvåg, Helmer & Finstad, Terje
(2007).
Electronic structure and bonding in thermoelectric skutterudites.
Unipub forlag.
ISSN 1501-7710.