Abstract
The increasing worldwide energy consumption calls for the design of more efficient energy systems. Thermoelectrics could be used to convert waste heat back to useful electric energy if only more efficient materials were available. The ideal thermoelectric material combines high electrical conductivity and thermopower with low thermal conductivity. In this regard, the intermetallic type-I clathrates show promise with their exceedingly low lattice thermal conductivities1. Here we report the successful incorporation of cerium as a guest atom into the clathrate crystal structure. In many simpler intermetallic compounds, this rare earth element is known to lead, through the Kondo interaction, to strong correlation phenomena including the occurrence of giant thermopowers at low temperatures2. Indeed, we observe a 50% enhancement of the thermopower compared with a rare-earth-free reference material. Importantly, this enhancement occurs at high temperatures and we suggest that a rattling-enhanced Kondo interaction3 underlies this effect.
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Change history
06 November 2013
In the version of this Letter originally published online, in Fig. 1a caption, '2a (6c)' should have read '2a (6d)'. This error has now been corrected in all versions of the Letter.
References
Toberer, E. S., Christensen, M., Iversen, B. B. & Snyder, G. J. High temperature thermoelectric efficiency in Ba8Ga16Ge30 . Phys. Rev. B 77, 075203 (2008).
Paschen, S. in Thermoelectrics Handbook (ed. Rowe, D. M.) Ch. 15 (CRC, 2006).
Hotta, T. Enhanced Kondo effect in an electron system dynamically coupled with local optical phonons. J. Phys. Soc. Jpn 76, 084702 (2007).
Christensen, M. et al. Avoided crossing of rattler modes in thermoelectric materials. Nature Mater. 7, 811â815 (2008).
Euchner, H. et al. Phononic filter effect of rattling phonons in the thermoelectric clathrate Ba8Ge40+xNi6âx . Phys. Rev. B 86, 224303 (2012).
Slack, G. A. in CRC Handbook of Thermoelectrics (ed. Rowe, D. M.) Ch. 34 (CRC, 1995).
Saramat, A. et al. Large thermoelectric figure of merit at high temperature in Czochralski-grown clathrate Ba8Ga16Ge30 . J. Appl. Phys. 99, 023708 (2006).
Anno, H., Hokazono, M., Kawamura, M., Nagao, J. & Matsubara, K. Thermoelectric properties of Ba8GaxGe46âx clathrate compounds. Proc. 21st Int. Conf. on Thermoelectrics 77â80 (Long Beach, 2002).
Rowe, D. M., Kuznetsov, V. L., Kuznetsova, L. A. & Min, G. Electrical and thermal transport properties of intermediate-valence YbAl3 . J. Phys. D 35, 2183â2186 (2002).
Sales, B. C. et al. Magnetic, transport, and structural properties of Fe1âxIrxSi. Phys. Rev. B 50, 8207â8213 (1994).
Jie, Q. et al. Electronic thermoelectric power factor and metal-insulator transition in FeSb2 . Phys. Rev. B 86, 115121 (2012).
ZlatiÄ, V. & Monnier, R. Theory of the thermoelectricity of intermetallic compounds with Ce or Yb ions. Phys. Rev. B 71, 165109 (2005).
Coleman, P. in Fundamentals and Theory Vol. 1 (eds Kronmüller, H. & Parkin, S.) 95â148 (Handbook of Magnetism and Advanced Magnetic Materials, Wiley, 2007).
Kawaguchi, T., Tanigaki, K. & Yasukawa, M. Silicon clathrate with an f-electron system. Phys. Rev. Lett. 85, 3189â3192 (2000).
Pacheco, V., Carrillo-Cabrera, W., Tran, V. H., Paschen, S. & Grin, Y. Comment on âsilicon clathrate with an f-electron systemâ. Phys. Rev. Lett. 87, 099601 (2001).
Kawaguchi, T., Tanigaki, K. & Yasukawa, M. Comment on âsilicon clathrate with an f-electron systemâ: Reply. Phys. Rev. Lett. 87, 099602 (2001).
Tang, X., Li, P., Deng, S. & Zhang, Q. High temperature thermoelectric transport properties of double-atom-filled clathrate compounds YbxBa8âxGa16Ge30 . J. Appl. Phys. 104, 013706 (2008).
Kovnir, K. et al. Introducing a magnetic guest to a tetrel-free clathrate: Synthesis, structure, and properties of EuxBa8âxCu16P30 (0â¤xâ¤1.5). Inorg. Chem. 50, 10387â10396 (2011).
Schäfer, H. On the problem of polar intermetallic compounds: The stimulation of E. Zintlâs work for the modern chemistry of intermetallics. Ann. Rev. Mater. Sci. 15, 1â42 (1985).
Aydemir, U. et al. Low-temperature thermoelectric, galvanomagnetic and thermodynamic properties of the type-I clatharate Ba8AuxSi46âx . Phys. Rev. B 84, 195137 (2011).
Fert, A. & Levy, P. M. Theory of the Hall effect in heavy-fermion compounds. Phys. Rev. B 36, 1907â1916 (1987).
Nguyen, L. T. K. et al. Atomic ordering and thermoelectric properties of the n-type clathrate Ba8Ni3.5Ge42.1â¡0.4 . Dalton Trans. 39, 1071â1077 (2010).
Nakatsuji, S. et al. Intersite coupling effects in a Kondo lattice. Phys. Rev. Lett. 89, 106402 (2002).
Candolfi, C. et al. High temperature thermoelectric properties of the type-I clathrate Ba8AuxSi46âx . J. Appl. Phys. 111, 043706 (2012).
Zeiringer, I. et al. The ternary system Au-Ba-Si: Clathrate solution, electronic structure, physical properties, phase eqilibria and crystal structures. Acta Mater. 60, 2324â2336 (2012).
Melânikov, V. I. Thermodynamics of the Kondo problem. JETP Lett. 35, 511â515 (1982).
Gegenwart, P., Si, Q. & Steglich, F. Quantum criticality in heavy-fermion metals. Nature Phys. 4, 186â197 (2008).
Junod, A., Jarlborg, T. & Muller, J. Heat-capacity analysis of a large number of A15-type compounds. Phys. Rev. B 27, 1568â1585 (1983).
Suekuni, K., Avila, M. A., Umeo, K. & Takabatake, T. Cage-size control of guest vibration and thermal conductivity in Sr8Ga16Si30âxGex . Phys. Rev. B 75, 195210 (2007).
Hewson, A. C. & Meyer, D. Numerical renormalization group study of the Anderson-Holstein impurity model. J. Phys. Condens. Matter 14, 427â445 (2002).
Sanada, S. et al. Exotic heavy-fermion state in filled skutterudite SmOs4Sb12 . J. Phys. Soc. Jpn 74, 246â249 (2005).
Costi, T. A. & ZlatiÄ, V. Charge Kondo anomalies in PbTe doped with Tl impurities. Phys. Rev. Lett. 108, 036402 (2012).
Hotta, T. & Ueda, K. Electric dipolar Kondo effect emerging from a vibrating magnetic ion. Phys. Rev. Lett. 108, 247214 (2012).
Andergassen, S., Costi, T. A. & ZlatiÄ, V. Mechanism for large thermoelectric power in molecular quantum dots described by the negative-U Anderson model. Phys. Rev. B 84, 241107(R) (2011).
Herrmann, R. F. W., Tanigaki, K., Kawaguchi, T., Kuroshima, S. & Zhou, O. Electronic structure of Si and Ge gold-doped clathrates. Phys. Rev. B 60, 13245â13248 (1999).
Acknowledgements
We acknowledge financial support from the Austrian Science Fund (projects P19458-N16, TRP 176-N22 and I623-N16) and the European Research Council (Advanced Grant QuantumPuzzle, no. 227378), and help from T. Pippinger and R. Miletich-Pawliczek (Vienna University) during single-crystal XRD measurements on LaâBAS. TEM images were made by J. Bernardi and M. Stöger-Pollach at USTEM (Vienna University of Technology).
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A.P. and S.P. designed the research. A.P. synthesized the material; A.S., M.I., R.S., M.W., H.W., K.N. and K.H. performed the measurements. A.P., A.S., H.W., K.H. and S.P. analysed the data. A.P., A.S. and S.P. prepared the manuscript.
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Prokofiev, A., Sidorenko, A., Hradil, K. et al. Thermopower enhancement by encapsulating cerium in clathrate cages. Nature Mater 12, 1096â1101 (2013). https://doi.org/10.1038/nmat3756
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DOI: https://doi.org/10.1038/nmat3756