Thermoelectric Properties of CoAsSb: An Experimental and Theoretical Study

Journal Article · Thu Jun 07 04:00:00 EDT 2018 · Chemistry of Materials

DOI:https://doi.org/10.1021/acs.chemmater.7b05170· OSTI ID:1465768

Tan, Xiaoyan; Devlin, Kasey P.; Deng, Xiaoyu; Kang, Chang-Jong; Croft, Mark; Frank, Corey E.; Pak, Chongin ^[1]; Lapidus, Saul ^[2]; Kauzlarich, Susan M.; Taufour, Valentin; Kotliar, Gabriel; Greenblatt, Martha

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1. Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
2. Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States

Polycrystalline samples of CoAsSb were prepared by annealing a stoichiometric mixture of the elements at 1073 K for two weeks. Synchrotron powder X-ray diffraction refinement indicated that CoAsSb adopts arsenopyrite-type structure with space group P21/c. Sb vacancies were observed both by elemental and structural analysis, which indicate CoAsSb0.883 composition. CoAsSb was thermally stable up to 1073 K without structure change, but decomposed at 1168 K. Thermoelectric properties were measured from 300 to 1000 K on a dense pellet. Electrical resistivity measurements revealed that CoAsSb is a narrow-band-gap semiconductor. The negative Seebeck coefficient indicated that CoAsSb is an n-type semiconductor, with the maximum value of -132.42 μV/K at 450 K. The overall thermal conductivity is between 2.9 W/m K and 6.0 W/m K in the temperature range of 300-1000 K, and the maximum value of figure of merit, zT, reaches 0.13 at 750 K. First principles calculations of the electrical resistivity and Seebeck coefficient confirmed n-type semiconductivity, with a calculated maximum Seebeck coefficient of -87 μV/K between 900 and 1000 K. The difference between experimental and calculated Seebeck coefficient was attributed to the Sb vacancies in the structure. The calculated electronic thermal conductivity is close to the experimental total thermal conductivity, and the estimated theoretical zT based solely on electronic thermal conductivity agrees with experimental values in the high temperature range, above 800 K. The effect of Sb vacancies on the electronic and transport properties are discussed.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: USDOE U.S. Department of Energy
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1465768
• Journal Information: Chemistry of Materials, Journal Name: Chemistry of Materials Journal Issue: 13 Vol. 30; ISSN 0897-4756
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English