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Title: Filling fraction of Yb in CoSb 3 Skutterudite studied by electron microscopy

Authors:
 [1]; ORCiD logo [2];  [2];  [3];  [2]
  1. Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204, USA, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China
  2. Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204, USA
  3. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1361813
Grant/Contract Number:
SC0001299
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 110; Journal Issue: 16; Related Information: CHORUS Timestamp: 2018-02-15 02:13:29; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics
Country of Publication:
United States
Language:
English

Citation Formats

Wang, Yumei, Mao, Jun, Jie, Qing, Ge, Binghui, and Ren, Zhifeng. Filling fraction of Yb in CoSb 3 Skutterudite studied by electron microscopy. United States: N. p., 2017. Web. doi:10.1063/1.4979937.
Wang, Yumei, Mao, Jun, Jie, Qing, Ge, Binghui, & Ren, Zhifeng. Filling fraction of Yb in CoSb 3 Skutterudite studied by electron microscopy. United States. doi:10.1063/1.4979937.
Wang, Yumei, Mao, Jun, Jie, Qing, Ge, Binghui, and Ren, Zhifeng. Mon . "Filling fraction of Yb in CoSb 3 Skutterudite studied by electron microscopy". United States. doi:10.1063/1.4979937.
@article{osti_1361813,
title = {Filling fraction of Yb in CoSb 3 Skutterudite studied by electron microscopy},
author = {Wang, Yumei and Mao, Jun and Jie, Qing and Ge, Binghui and Ren, Zhifeng},
abstractNote = {},
doi = {10.1063/1.4979937},
journal = {Applied Physics Letters},
number = 16,
volume = 110,
place = {United States},
year = {Mon Apr 17 00:00:00 EDT 2017},
month = {Mon Apr 17 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1063/1.4979937

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  • Filling voids with rare earth atoms is an effective way to lowering thermal conductivity which necessarily enhances thermoelectric properties of skutterudite compounds. Yb atom is one of the most effective species among the rare earth atoms for filling the voids in the skutterudite structure due to a large atomic mass, radius and it is intermediate valence state. In this work, we aim to find the best filling partners for Yb using different combinations of Ce and In as well as to optimize actual filling fraction in order to achieve high values of ZT. The traditional method of synthesis relying onmore » melting-annealing and followed by spark plasma sintering was used to prepare all samples. The thermoelectric properties of four samples of Yb{sub 0.2}In{sub 0.2}Co{sub 4}Sb{sub 12}, Yb{sub 0.2}Ce{sub 0.15}Co{sub 4}Sb{sub 12}, Yb{sub 0.2}Ce{sub 0.15}In{sub 0.2}Co{sub 4}Sb{sub 12}, and Yb{sub 0.3}Ce{sub 0.15}In{sub 0.2}Co{sub 4}Sb{sub 12} (nominal) were examined based on the Seebeck coefficient, electrical conductivity, thermal conductivity, and Hall coefficient. Hall coefficient and Seebeck coefficient signs confirm that all samples are n-type skutterudite compounds. Carrier density increases with the increasing Yb+Ce content. A high power factor value of 57.7 {mu}W/K{sup 2}/cm for Yb{sub 0.2}Ce{sub 0.15}Co{sub 4}Sb{sub 12} and a lower thermal conductivity value of 2.82 W/m/K for Yb{sub 0.2}Ce{sub 0.15}In{sub 0.2}Co{sub 4}Sb{sub 12} indicate that small quantities of Ce with In may be a good partner to Yb to reduce the thermal conductivity further and thus enhance the thermoelectric performance of skutterudites. The highest ZT value of 1.43 was achieved for Yb{sub 0.2}Ce{sub 0.15}In{sub 0.2}Co{sub 4}Sb{sub 12} triple-filled skutterudite at 800 K. - Graphical abstract: Thermoelectric figure of merit of Yb{sub x}In{sub y}Ce{sub z}Co{sub 4}Sb{sub 12} (0{<=}x,y,z{<=}0.18 actual) compounds versus temperature. Highlights: Black-Right-Pointing-Pointer TE properties of Yb,In,Ce multiple-filled Yb{sub x}In{sub y}Ce{sub z}Co{sub 4}Sb{sub 12} skutterudites were investigated. Black-Right-Pointing-Pointer Thermal conductivity is strongly suppressed by multiple filling of Yb, Ce and In. Black-Right-Pointing-Pointer Small amounts of Ce and In with Yb are beneficial for the enhancement of TE performance. Black-Right-Pointing-Pointer The highest ZT=1.43 was achieved with Yb{sub 0.07}In{sub 0.094}Ce{sub 0.065}Co{sub 4}Sb{sub 11.92} at 800 K.« less
  • Historically, the improved thermoelectric performance of skutterudite compounds has largely been driven by the incorporation of electropositive donors on interstitial sites. These 'rattlers' serve to optimize both electronic and thermal properties by tuning the carrier concentration and scattering phonons. In this work, we show that interstitial bromine can be incorporated into CoSb3 and assess the impact on electronic and thermal transport. In contrast to prior high pressure syntheses with iodine, interstitial bromine incorporation is achieved at ambient pressure. Transport properties are stable up to at least 375 degrees C. Bromine serves as an electronegative acceptor and can induce degenerate (>5more » x 1019 cm-3) hole densities. In contrast to other p-type skutterudite compositions, bromine preserves the intrinsically high hole mobility of CoSb3 while significantly reducing the lattice thermal conductivity. The development of a stable p-type dopant for the interstitial filler site enables the development of skutterudites with both donor and acceptor interstitials to maximize phonon scattering while maintaining the high mobility of CoSb3.« less
  • The complex doping behavior of Ga and In in CoSb 3 has been investigated using ab initio total-energy calculations and thermodynamics. The formation energies of void filling, Sb substitution and complex dual-site occupancy defects with different charge states, and their dependence on chemical potentials of species, were studied. Results show that Ga predominantly forms dual-site 2Ga VF–Ga Sb defects and substitutes for Sb only at very high Fermi levels or electron concentrations. In, on the other hand, can play multiple roles in skutterudites, including filling in the crystalline voids, substituting for Sb atoms or forming dual-site occupancy, among which themore » fully charge-compensated dual-site defects (2In VF–In Sb and 4In VF–2In Sb) are dominant. The equilibrium concentration ratio of impurities at void-filling sites to those at Sb-substitution sites for Ga-doped CoSb 3 is very close to be 2:1, while this value markedly deviates from 2:1 for In-doped CoSb 3. Furthermore, the 2:1 ratio of Ga doping in CoSb 3 leads to low electron concentration (~2 × 10 19 cm –3) and makes the doped system a semiconductor.« less
  • Thermoelectric properties of nanostructured skutterudite CoSb{sub 3} have been reported. Nanosized CoSb{sub 3} powders were synthesized through a solvothermal route. The bulk materials with average grain sizes of 250 and 150 nm were prepared by hot pressing and spark plasma sintering from the solvothermally synthesized CoSb{sub 3} powders. Both the samples show n-type conduction and the thermal conductivities are reduced compared with that of the sample prepared by the melt-annealing/hot pressing method. A thermoelectric figure of merit of 0.61 has been obtained for the unfilled CoSb{sub 3} skutterudite by spark plasma sintering, which indicates that nanostructuring is an effective waymore » to improve the thermoelectric properties of skutterudite compounds.« less
  • The experimental charge density of nondoped CoSb{sub 3} has been determined by the maximum entropy method (MEM) using low temperature (10 K), short wavelength (0.42 A), and high-resolution (d{sub min}=0.33 A) synchrotron x-ray powder diffraction data measured at SPring-8, Japan. The MEM charge density clearly reveals three types of charge density overlap between atoms in CoSb{sub 3}. The four Sb atoms form an Sb{sub 4} ring, and the MEM charge densities at two types of Sb-Sb midpoints are 0.35 and 0.50 e A{sup -3}. The charge density overlap between the Co and Sb atoms at the midpoint is 0.52 emore » A{sup -3}, which is larger than the values observed at the Sb-Sb midpoints. The nature of the chemical bonding observed in the present MEM charge density is consistent with a previous theoretical study by Lefebvre-Devos et al. [Phys. Rev. B 63, 125110 (2001)].« less