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Title: High-performance n-type Yb xCo 4Sb 12: from partially filled skutterudites towards composite thermoelectrics

The filling fraction limit (FFL) of skutterudites, that is, the complex balance of formation enthalpies among different species, is an intricate but crucial parameter for achieving high thermoelectric performance. In this work, we synthesized a series of Yb xCo 4Sb 12 samples with x=0.2–0.6 and systemically studied the FFL of Yb, which is still debated even though this system has been extensively investigated for decades. Our combined experimental efforts of X-ray diffraction, microstructural and quantitative compositional analyses clearly reveal a Yb FFL of ~0.29 in CoSb 3, which is consistent with previous theoretical calculations. For the excess Yb in samples with x>0.35 mainly form metallic YbSb 2 precipitates, the Fermi level increases significantly and thus increases the electrical conductivity and decreasing the Seebeck coefficient. Our result is further corroborated by the numerical calculations based on the Bergman’s composite theory, which accurately reproduces the transport properties of the x>0.35 samples based on nominal Yb 0.35Co 4Sb 12 and YbSb 2 composites. A maximum ZT of 1.5 at 850 K is achieved for Yb 0.3Co 4Sb 12, which is the highest value for a single-element-filled CoSb 3. The high ZT originates from the high-power factor (in excess of 50 μW cm -Kmore » -2) and low lattice thermal conductivity (well below 1.0 W m -K -1). More importantly, the large average ZTs, for example, ~1.05 for 300–850 K and ~1.27 for 500–850 K, are comparable to the best values for n-type skutterudites. The high thermoelectric and thermomechanical performances and the relatively low air and moisture sensitivities of Yb make Yb-filled CoSb 3, a promising candidate for large-scale power generation applications.« less
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  1. Univ. of Washington, Seattle, WA (United States). Materials Science adn Engineering Dept.
  2. General Motors Research and Development, Warren, MI (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
NPG Asia Materials (Online)
Additional Journal Information:
Journal Name: NPG Asia Materials (Online); Journal Volume: 8; Journal Issue: 7; Journal ID: ISSN 1884-4057
Nature Publishing Group Asia
Research Org:
Univ. of Washington, Seattle, WA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
OSTI Identifier: