Unveiling the phonon scattering mechanisms in half-Heusler thermoelectric compounds

Half-Heusler (HH) compounds are among the most promising thermoelectric (TE) materials for large-scale applications due to their superior properties such as high power factor, excellent mechanical and thermal reliability, and non-toxicity. Their only drawback is the remaining-high lattice thermal conductivity. Various mechanisms were reported with claimed effectiveness to enhance the phonon scattering of HH compounds including grain-boundary scattering, phase separation, and electron–phonon interaction. In this work, however, we show that point-defect scattering has been the dominant mechanism for phonon scattering other than the intrinsic phonon–phonon interaction for ZrCoSb and possibly many other HH compounds. Induced by the charge-compensation effect, the formation of Co/4d Frenkel point defects is responsible for the drastic reduction of lattice thermal conductivity in ZrCoSb1−xSnx. Our work systematically depicts the phonon scattering profile of HH compounds and illuminates subsequent material optimizations

Influence of Defects on the Schottky Barrier Height at BaTiO₃/RuO₂ Interfaces

The Schottky barrier formation between polycrystalline acceptor‐doped BaTiO₃ and high work function RuO₂ is studied using photoelectron spectroscopy. Schottky barrier heights for electrons of ≈1.4 eV are determined, independent of doping level and oxygen vacancy concentration of the substrates. The insensitivity of the barrier height is related to the high permittivity of BaTiO₃, which results in space‐charge regions (SCRs) being considerably wider than the inelastic mean free path of the photoelectrons. SCRs at any kind of interface should, therefore, be more important for the electronic and ionic conductivities in BaTiO₃ than in materials with lower permittivity. A Ba‐rich phase at the surface of reduced acceptor‐doped BaTiO₃ is also identified, which is explained by the formation of Ti vacancies in the 2D electron gas region at the surface

Fabrication of porous rhodium nanotube catalysts by electroless plating

A versatile electroless plating procedure for the fabrication of rhodium nanomaterials was developed, leading to deposits consisting of loosely agglomerated metal nanoparticles. By using carbon black as the substrate, supported rhodium nanoparticle clusters were obtained. In combination with ion track etched polymer templates, the deposition protocol allowed the first direct synthesis of rhodium nanotubes. Polymer dissolution provided access to well defined, supportless and free-standing rhodium nanotubes of nearly cylindrical shape, 300 nm opening diameter, 28 μm length and 50 nm wall thickness. The characterization by SEM, TEM, EDS and XRD confirmed the purity of the deposit, displayed a small particle size of approximately 3 nm and revealed gaps in the range of a few nanometers between the rhodium particles. BET analysis verified the presence of pores of <5 nm. To evaluate the electrocatalytic potential of the rhodium nanotubes, they were applied in the amperometric detection of hydrogen peroxide. Compared to classical nanoparticle-based sensing concepts, improved performance parameters (sensitivity, detection limit, and linear range) could be achieved

Unveiling the phonon scattering mechanisms in half-Heusler thermoelectric compounds

© The Royal Society of Chemistry. Half-Heusler (HH) compounds are among the most promising thermoelectric (TE) materials for large-scale applications due to their superior properties such as high power factor, excellent mechanical and thermal reliability, and non-toxicity. Their only drawback is the remaining-high lattice thermal conductivity. Various mechanisms were reported with claimed effectiveness to enhance the phonon scattering of HH compounds including grain-boundary scattering, phase separation, and electron-phonon interaction. In this work, however, we show that point-defect scattering has been the dominant mechanism for phonon scattering other than the intrinsic phonon-phonon interaction for ZrCoSb and possibly many other HH compounds. Induced by the charge-compensation effect, the formation of Co/4d Frenkel point defects is responsible for the drastic reduction of lattice thermal conductivity in ZrCoSb1-xSnx. Our work systematically depicts the phonon scattering profile of HH compounds and illuminates subsequent material optimizations. This journal i

HIRACLES : HIgh-Resolution imAgery for CLiff Erosion Studies – utilisation des images Pléiades pour le suivi de l’érosion du front de falaise

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Contribution de l’imagerie satellite oblique (Pléiades) au suivi et à la compréhension de l’érosion des falaises

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HIRACLES : HIgh-Resolution imAgery for CLiff Erosion Studies – utilisation des images Pléiades pour le suivi de l’érosion du front de falaise

National audienc

HIRACLES : HIgh-Resolution imAgery for CLiff Erosion Studies – utilisation des images Pléiades pour le suivi de l’érosion du front de falaise

National audienc

Contribution de l’imagerie satellite oblique (Pléiades) au suivi et à la compréhension de l’érosion des falaises

National audienc