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Computational Studies of Novel Thermoelectric Materials

Published online by Cambridge University Press:  15 February 2011

D.J. Singh ,
I.I. Mazin ,
S.G. KIM  and
L. Nordstrom
D.J. Singh
Affiliation:
Code 6691, Naval Research Laboratory, Washington, DC 20375
I.I. Mazin
Affiliation:
CSI, George Mason University and Code 6691 NRL, Washington, DC 20375
S.G. KIM
Affiliation:
UES Inc. and Code 6691 NRL, Washington, DC 20375
L. Nordstrom
Affiliation:
Physics Department, Uppsala University, Box 530, S-75121 Uppsala, Sweden
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Abstract

The thermoelectric properties of La-filled skutterudites and β-Zn4Sb3 are discussed from the point of view of their electronic structures. These are calculated from first principles within the local density approximation. The electronic structures are in turn used determine transport related quantities. β-Zn4Sb3 is found to be metallic with a complex Fermi surface topology, which yields a non-trivial dependence of the Hall concentration on the band filling. Calculations of the variation with band filling are used to extract the carrier concentration from the experimental Hall number. At this band filling, which corresponds to 0.1 electrons per 22 atom unit cell, we calculate a Seebeck coefficient and temperature dependence in good agreement with the experimental value. The high Seebeck coefficients in a metallic material are remarkable, and arise because of the strong energy dependence of the Fermiology near the experimental band filling. Virtual crystal calculations for La(Fe,Co)4Sb12 show that the system obeys almost perfect rigid band behavior with varying Co concentration, and has a substantial band gap at a position corresponding to the composition LaFe3CoSb12. The valence band maximum occurs at the Γ point and is due to a singly degenerate dispersive (Fe,Co)-Sb band, which by itself would not be favorable for TE. However, very flat transition metal derived bands occur in close proximity and become active as the doping level is increased, giving a non-trivial dependence of the properties on carrier concentration and explaining the favorable TE properties.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 478: Symposium Q – Thermoelectric Materials - New Directions and Approaches , 1997 , 187
Copyright
Copyright © Materials Research Society 1997

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