High Seebeck Coefficient and Unusually Low Thermal Conductivity Near Ambient Temperatures in Layered Compound Yb 2– x Eu x CdSb 2
- Department of Chemistry, University of California, One Shields Avenue, Davis, California 95616, United States
- Department of Chemistry, University of California, One Shields Avenue, Davis, California 95616, United States, IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao, Spain
- Department of Physics, University of California, One Shields Avenue, Davis, California 95616, United States
- Department of Physics, Colorado School of Mines, Golden, Colorado 80401, United States
Zintl phases are promising thermoelectric materials because they are composed of both ionic and covalent bonding, which can be independently tuned. An efficient thermoelectric material would have regions of the structure composed of a high-mobility compound semiconductor that provides the “electron–crystal” electronic structure, interwoven (on the atomic scale) with a phonon transport inhibiting structure to act as the “phonon–glass”. The phonon–glass region would benefit from disorder and therefore would be ideal to house dopants without disrupting the electron–crystal region. The solid solution of the Zintl phase, Yb2–xEuxCdSb2, presents such an optimal structure, and here we characterize its thermoelectric properties above room temperature. Thermoelectric property measurements from 348 to 523 K show high Seebeck values (maximum of ~269 μV/K at 523 K) with exceptionally low thermal conductivity (minimum ~0.26 W/m K at 473 K) measured via laser flash analysis. Speed of sound data provide additional support for the low thermal conductivity. Density functional theory (DFT) was employed to determine the electronic structure and transport properties of Yb2CdSb2 and YbEuCdSb2. Lanthanide compounds display an f-band well below (~2 eV) the gap. This energy separation implies that f-orbitals are a silent player in thermoelectric properties; however, we find that some hybridization extends to the bottom of the gap and somewhat renormalizes hole carrier properties. Changes in the carrier concentration related to the introduction of Eu lead to higher resistivity. A zT of ~0.67 at 523 K is demonstrated for Yb1.6Eu0.4CdSb2 due to its high Seebeck, moderate electrical resistivity, and very low thermal conductivity.
- Research Organization:
- Univ. of California, Davis, CA (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- Contributing Organization:
- National Energy Research Scientific Computing Center
- Grant/Contract Number:
- AC02-05CH11231; NA0002908
- OSTI ID:
- 1416091
- Alternate ID(s):
- OSTI ID: 1508301; OSTI ID: 1753986
- Journal Information:
- Chemistry of Materials, Journal Name: Chemistry of Materials Vol. 30 Journal Issue: 2; ISSN 0897-4756
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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