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Thermoelectric properties of Ag 2 S b 2 G e 46 − x D y x T e 50 alloys with high power factor
Author(s) -
Levin E. M.,
Hanus R.,
Hanson M.,
Straszheim W. E.,
SchmidtRohr K.
Publication year - 2013
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201330217
Subject(s) - seebeck coefficient , thermoelectric effect , materials science , electrical resistivity and conductivity , thermal conductivity , thermoelectric materials , condensed matter physics , atmospheric temperature range , analytical chemistry (journal) , figure of merit , chemistry , thermodynamics , optoelectronics , physics , chromatography , quantum mechanics , composite material
A comprehensive study of GeTe‐based materials where Ge is replaced by 2 at.% Ag, 2 at.% Sb, and additionally by 1 or 2 at.% Dy (Ag 2 Sb 2 Ge 46 − x Dy x Te 50 alloys) has been conducted using Seebeck coefficient, electrical resistivity, and thermal conductivity measurements in the temperature range of 300–750 K, and X‐ray diffraction (XRD) and 125 Te NMR at 300 K. According to our data, at ∼720 K, GeTe, a self‐doping degenerate semiconductor, exhibits the highest known power factor (PF) among tellurides, 42 μW cm −1 K −2 , but due to high thermal conductivity, the thermoelectric figure of merit, ZT , is relatively low, ∼0.8. Replacement of Ge in GeTe by [Ag + Sb] and Dy enhances the Seebeck coefficient and produces a small increase in carrier concentration deduced from 125 Te NMR spin–lattice relaxation. The PF of Ag 2 Sb 2 Ge 45 Dy 1 Te 50 at ∼720 K is found to be still high, 40 μW cm −1 K −2 , and due to a reduction in thermal conductivity, ZT reaches 1.2. Our data show that relatively high ZT values in tellurides can be obtained primarily due to high PF while thermal conductivity is moderate. The enhancement of the Seebeck coefficient observed in Ag 2 Sb 2 Ge 46 − x Dy x Te 50 alloys can be attributed to energy filtering due potential barriers formed by [Ag + Sb] and rare‐earth Dy atoms.