Nanostructuring of p- and n-type skutterudites reaching figures of merit of approximately 1.3 and 1.6, respectively

Rogl, Gerda; Grytsiv, A.; Rogl, P.; Bauer, E.; Hochenhofer, M.; Anbalagan, R.; Mallik, Ramesh Chandra; Schafler, Erhard

doi:10.1016/j.actamat.2014.05.051

Cited by 111 publications

(89 citation statements)

References 105 publications

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“…The improved performance of some multiply filled skutterudites 8,[36][37][38][39][40][41][42][43][44][45][46] may be explained in part from nanodomains with avoided crossings at different qvectors. However, in many cases the concentrations of some filler atom are low and in that case defect scattering should also play an important role.…”

Section: Discussionmentioning

confidence: 99%

Modeling correlated motion in filled skutterudites

Keiber

Bridges

2015

Phys. Rev. B

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Recent extended X-ray absorption fine structure (EXAFS) studies suggest that in skutterudites, the nearly square rings (such as As4 in CeFe4As12) are quite rigid and may vibrate with low energy modes in one direction, similar to "rattler" atom vibrations. That work suggests that the motions of the square rings and the rattler atoms are coupled. In addition, for LnCu3Ru4O12, the second neighbor pairs about Ln have stiffer effective springs than the nearest neighbor pairs. To investigate these systems, a one dimensional, four mass, linear chain spring model is developed to describe the recent experimental results, and provide insight about the low energy vibrations in such systems. Our model solves the resulting coupled network of overlapping weak and strong springs and determines the eigenfrequencies and eigenvectors. The dispersion curves show an acoustic mode, two different low energy optical rattling modes involving both the rattler and square, and a non interacting optical mode. Each rattler mode can couple to the acoustic mode, which generates avoided crossings characterized by flattening of the modes; this has important consequences for thermal transport. From these results we calculate atomic correlation functions and the Debye-Waller-like function used in EXAFS, σ 2 , as a function of temperature. These calculations show that for the rattler-neighbor pairs, σ 2 is a sum over several modes; it is not the result of a single mode. The inverse slope of σ 2 (T) at high T provides a measure of the effective spring constants, and the results show that for small direct spring constants the effective spring constant can be significantly larger than the direct spring constants. The locations of the avoided crossings (between rattler modes and the acoustic mode) in q-space can be tuned by the choice of both the rattler and the square atoms. Consequently, it may be possible to further reduce the thermal conductivity using a mixture of nanoparticles, each with avoided crossings at different positions in q-space.

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Section: Discussionmentioning

confidence: 99%

Modeling correlated motion in filled skutterudites

Keiber

Bridges

2015

Phys. Rev. B

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“…Our Yb-filled samples show excellent TE performance with a maximum ZT of 1.5 at 850 K for Yb 0.3 Co 4 Sb 12 (nominal composition), outperforming all previously reported single-element-filled skutterudites, 12,15,17,[26][27][28][29] and having comparable performance to the best reported values for any n-type skutterudites. 5,8,30 For power generation applications, the average ZT in the temperature range of use is more important to achieve high TE conversion efficiency. 3, 31 We therefore compared the average ZTs of Yb 0.3 Co 4 Sb 12 with those of the best reported ZT of triple-filled CoSb 3 , 5 as shown in Figure 3b.…”

Section: Te Transport Propertiesmentioning

confidence: 99%

“…3,4 Skutterudite antimonide is one of the most promising candidates for intermediate temperature TE power generation (500-900 K) owing to the availability of both high-performance n-and p-type compositions within this material class with excellent thermomechanical properties and relatively low-cost and abundant constituent elements (compared with the state-of-the-art Bi 2 Te 3 and PbTe). [4][5][6][7][8][9] Guest filling in the structural nanovoids to form the so-called filled skutterudites (i.e., R y (Co,Fe) 4 Sb 12 , where R represents the filler and y the filling fraction) is the best strategy for enhancing the TE figure of merit ZT as the fillers both act to control carrier concentration and significantly suppress the propagation of heat-carrying phonons. 6,7 Many elements can be partially filled in CoSb 3 , such as alkali, alkaline earth, rare earth, and group IIIA elements.…”

Section: Introductionmentioning

confidence: 99%

High-performance n-type YbxCo4Sb12: from partially filled skutterudites towards composite thermoelectrics

et al. 2016

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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 x Co 4 Sb 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. The excess Yb in samples with x40.35 mainly form metallic YbSb 2 precipitates, significantly raising the Fermi level and thus increasing the electrical conductivity and decreasing the Seebeck coefficient. This result is further corroborated by the numerical calculations based on the Bergman's composite theory, which accurately reproduces the transport properties of the x40.35 samples based on nominal Yb 0.35 Co 4 Sb 12 and YbSb 2 composites. A maximum ZT of 1.5 at 850 K is achieved for Yb 0.3 Co 4 Sb 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-K − 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.

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“…Recently, thermoelectric materials have shown great advances in the figure of merit (ZT), especially for intermediate-temperature (600~1000 K) thermoelectric materials, through nano-structured material, band structure engineering, and grain boundary engineering. Skutterudite, a well-known intermediate-temperature thermoelectric material, shows a relatively high ZT of 1.6 at 800 K for n-type case, and 1.3 at 775 K for p-type case by nano-structuring [1]. PbTe also shows peak ZT of 2.5 at 923 K, and average ZT 1.67 between 300 and 900 K which is due largely to its band structure engineering and nano-structuring [2].…”

Section: Introductionmentioning

confidence: 98%

Multi-Layer Metallization Structure Development for Highly Efficient Polycrystalline SnSe Thermoelectric Devices

et al. 2017

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Abstract:Recently, SnSe material with an outstanding high ZT (Figure of merit) of 2.6 has attracted much attention due to its strong applicability for highly efficient thermoelectric devices. Many studies following the first journal publication have been focused on SnSe materials, not on thermoelectric devices. Particularly, to realize highly efficient intermediate-temperature (600~1000 K) thermoelectric modules with this promising thermoelectric material, a more thermally and electrically reliable interface bonding technology needs to be developed so that the modules can stably perform their power generation in this temperature range. In this work, we demonstrate several approaches to develop metallization layers on SnSe thermoelectric legs. The single-layer metallization shows limitations in their electrical contact resistances and elemental diffusions. The Ag/Co/Ti multi-layer metallization results in lowering their electrical contact resistances, in addition to providing more robust interfaces. Moreover, it is found to maintain the interfacial characteristics without any significant degradation, even after heat treatment at 723 K for 20 h. These results can be effectively applied in the fabrication of thermoelectric devices or modules that are made of the SnSe thermoelectric materials.

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Nanostructuring of p- and n-type skutterudites reaching figures of merit of approximately 1.3 and 1.6, respectively

Cited by 111 publications

References 105 publications

Modeling correlated motion in filled skutterudites

Modeling correlated motion in filled skutterudites

High-performance n-type YbxCo4Sb12: from partially filled skutterudites towards composite thermoelectrics

Multi-Layer Metallization Structure Development for Highly Efficient Polycrystalline SnSe Thermoelectric Devices

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