Charge carrier effective mass and concentration derived from combination of Seebeck coefficient and ${}^{125}\mathrm{Te}$ NMR measurements in complex tellurides
Abstract
Thermoelectric materials utilize the Seebeck effect to convert heat to electrical energy. The Seebeck coefficient (thermopower), S, depends on the free (mobile) carrier concentration, n, and effective mass, m*, as S ~ m*/n^{2/3}. The carrier concentration in tellurides can be derived from ^{125}Te nuclear magnetic resonance (NMR) spinlattice relaxation measurements. The NMR spinlattice relaxation rate, 1/T_{1}, depends on both n and m* as 1/T_{1}~(m*)^{3/2}n (within classical MaxwellBoltzmann statistics) or as 1/T1~(m*)^{2}n^{2/3} (within quantum FermiDirac statistics), which challenges the correct determination of the carrier concentration in some materials by NMR. Here it is shown that the combination of the Seebeck coefficient and ^{125}Te NMR spinlattice relaxation measurements in complex tellurides provides a unique opportunity to derive the carrier effective mass and then to calculate the carrier concentration. This approach was used to study Ag_{x}Sb_{x}Ge_{50–2x}Te_{50}, wellknown GeTebased highefficiency telluriumantimonygermaniumsilver thermoelectric materials, where the replacement of Ge by [Ag+Sb] results in significant enhancement of the Seebeck coefficient. Thus, values of both m* and n derived using this combination show that the enhancement of thermopower can be attributed primarily to an increase of the carrier effective mass and partially to a decrease of the carrier concentration when the [Ag+Sb] content increases.
 Authors:

 Ames Lab. and Iowa State Univ., Ames, IA (United States)
 Publication Date:
 Research Org.:
 Ames Laboratory (AMES), Ames, IA (United States)
 Sponsoring Org.:
 USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC22)
 OSTI Identifier:
 1278781
 Alternate Identifier(s):
 OSTI ID: 1259584
 Report Number(s):
 ISJ9009
Journal ID: ISSN 24699950; PRBMDO
 Grant/Contract Number:
 AC0207CH11358
 Resource Type:
 Accepted Manuscript
 Journal Name:
 Physical Review B
 Additional Journal Information:
 Journal Volume: 93; Journal Issue: 24; Journal ID: ISSN 24699950
 Publisher:
 American Physical Society (APS)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Ag_{x}Sb_{x}Ge_{50–2x}Te_{50} (TAGS); Seebeck coefficient; ^{125}Te NMR spinlattice relaxation time; charge carrier effective mass and concentration
Citation Formats
Levin, E. M. Charge carrier effective mass and concentration derived from combination of Seebeck coefficient and Te125 NMR measurements in complex tellurides. United States: N. p., 2016.
Web. doi:10.1103/PhysRevB.93.245202.
Levin, E. M. Charge carrier effective mass and concentration derived from combination of Seebeck coefficient and Te125 NMR measurements in complex tellurides. United States. doi:10.1103/PhysRevB.93.245202.
Levin, E. M. Mon .
"Charge carrier effective mass and concentration derived from combination of Seebeck coefficient and Te125 NMR measurements in complex tellurides". United States. doi:10.1103/PhysRevB.93.245202. https://www.osti.gov/servlets/purl/1278781.
@article{osti_1278781,
title = {Charge carrier effective mass and concentration derived from combination of Seebeck coefficient and Te125 NMR measurements in complex tellurides},
author = {Levin, E. M.},
abstractNote = {Thermoelectric materials utilize the Seebeck effect to convert heat to electrical energy. The Seebeck coefficient (thermopower), S, depends on the free (mobile) carrier concentration, n, and effective mass, m*, as S ~ m*/n2/3. The carrier concentration in tellurides can be derived from 125Te nuclear magnetic resonance (NMR) spinlattice relaxation measurements. The NMR spinlattice relaxation rate, 1/T1, depends on both n and m* as 1/T1~(m*)3/2n (within classical MaxwellBoltzmann statistics) or as 1/T1~(m*)2n2/3 (within quantum FermiDirac statistics), which challenges the correct determination of the carrier concentration in some materials by NMR. Here it is shown that the combination of the Seebeck coefficient and 125Te NMR spinlattice relaxation measurements in complex tellurides provides a unique opportunity to derive the carrier effective mass and then to calculate the carrier concentration. This approach was used to study AgxSbxGe50–2xTe50, wellknown GeTebased highefficiency telluriumantimonygermaniumsilver thermoelectric materials, where the replacement of Ge by [Ag+Sb] results in significant enhancement of the Seebeck coefficient. Thus, values of both m* and n derived using this combination show that the enhancement of thermopower can be attributed primarily to an increase of the carrier effective mass and partially to a decrease of the carrier concentration when the [Ag+Sb] content increases.},
doi = {10.1103/PhysRevB.93.245202},
journal = {Physical Review B},
number = 24,
volume = 93,
place = {United States},
year = {2016},
month = {6}
}
Web of Science