Publikationen

Influence of shear strain on HPT-processed n-type skutterudites yielding ZT=2.1

Autor(en)
Gerda Rogl, Sanyukta Ghosh, Oliver Renk, Kunio Yubuta, Andriy Grytsiv, Erhard Schafler, Michael Zehetbauer, Ramesh C. Mallik, Ernst Bauer, Peter Rogl
Abstrakt

After our successful new and energy-saving production route to prepare bulk skutterudites with high ZTs from commercial powders via cold pressing (CP) and high-pressure torsion (HPT), we present in this paper a detailed study of the influence of shear strain and the preparation parameters, especially the temperature, on the micro-structural, thermoelectric and mechanical properties by analyzing specimens cut from various positions of the HPT disks of (Sm,Mm)0.15Co4Sb12. Across these large discs (30 mm in diameter and about 1 mm thickness) the shear strain γ rises linearly from the center of the sample to the rim reaching γ ∼ 450 (for 5 revolutions), a value first time realized for skutterudites. HPT-straining is essential for the introduction of high densities of crystal lattice defects, particularly dislocations, which result in a significant refining of the grains. Whereas the processing temperature mainly influences the density of the HPT consolidated samples and as a consequence, physical and mechanical properties, the applied shear strain rules the thermoelectric parameters. As an important feature, the Seebeck coefficient remained roughly unchanged under strain. Although the increasing shear strain caused the thermal conductivity to significantly decrease, this beneficial effect is accompanied by a concomitant significant increase of the electrical resistivity. Consequently, the interplay of the two controversial influences results in a maximum and record high thermoelectric figure of merit ZT ∼2.1.

Organisation(en)
Institut für Materialchemie, Dynamik Kondensierter Systeme, Physik Nanostrukturierter Materialien
Externe Organisation(en)
Indian Institute of Science, Montanuniversität Leoben, Tohoku University, Technische Universität Wien
Journal
Journal of Alloys and Compounds
Band
855
Anzahl der Seiten
10
ISSN
0925-8388
DOI
https://doi.org/10.1016/j.jallcom.2020.157409
Publikationsdatum
02-2021
Peer-reviewed
Ja
ÖFOS 2012
104011 Materialchemie, 103018 Materialphysik
Schlagwörter
ASJC Scopus Sachgebiete
Mechanics of Materials, Mechanical Engineering, Metals and Alloys, Materials Chemistry
Link zum Portal
https://ucris.univie.ac.at/portal/de/publications/influence-of-shear-strain-on-hptprocessed-ntype-skutterudites-yielding-zt21(c7403f07-439b-40f3-9be7-156576fd21a0).html