Realization of high thermoelectric performance in n-type partially filled skutterudites
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Realization of high thermoelectric performance in n-type partially filled skutterudites Xun Shi,a) Shengqiang Bai, Lili Xi, Jiong Yang, Wenqing Zhang,b) and Lidong Chen State Key Laboratory of High Performance Ceramics and Superfine Microstructure and CAS Key Laboratory of Energy-conversion Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China
Jihui Yang Chemical Sciences and Materials Systems Laboratory, GM R&D Center, Warren, Michigan 48090 (Received 17 December 2010; accepted 28 February 2011)
Skutterudites are among the most exciting thermoelectric (TE) materials that could be used for various intermediate temperature applications. This study summarized our recent work on n-type partially filled skutterudites. By combining theoretical and experimental approaches, we revealed the underlying mechanism of void filling in the intrinsic lattice voids in CoSb3. With that, the electronegativity selection rule is established for the current stable filled skutterudites and further used for the discovery of a few novel filled CoSb3 compounds. The correlation between the thermal/ electrical transport properties and impurity fillers in n-type partially filled skutterudites was also carefully investigated. Our results provide fundamental understanding to how those filler impurities affect electronic structures and lattice dynamics. Based on these basic understanding on transport mechanisms and sophisticated strategy in materials synthesis, TE figure of merit for n-type materials were continually increased from 1.1 to 1.4 and then to 1.7 for single-, double-, and triple-filled skutterudites. I. INTRODUCTION
Thermoelectric (TE) techniques have a great potential for applications in high-efficiency heat-to-electricity conversion in waste heat recovery and solid state heating and cooling.1,2 There are several unique advantages in TE applications such as no moving parts, low maintenance cost, easy integration with other energy conversion devices, and long-term stability. The efficiency of TE materials is governed by the dimensionless TE figure of merit ZT 5 S2T/qj, where S is the thermopower, q is the electrical resistivity, T is the absolute temperature, and j is the thermal conductivity. The key and main goal in TE material research is to improve ZT through maximizing the thermopower while minimizing the electrical resistivity and thermal conductivity. Recent improvements in complex TE materials have led to many advances.2 Enhanced ZT values have been reported for several classes of materials, including superlattices,3,4 nanostructured materials,5,6 and bulk materials.7–10 The ZTs in bulk materials are improved quickly after 1990s (see Fig. 1), with some of them being reported but not confirmed to be above 2.0. At the search for promising TE materials, skutterudites have emerged as prospective candidates for many Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2011.84 J. Mater. Res., Vol. 26, No. 15, Aug 14, 2011
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