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Chen, Baoxing; Xu, Jun; Uher, Ctirad; Morelli, Donald T.; Meisner, G. P.; Fleurial, J. P.; Caillat, T.; Borshchevsky, A.

doi:10.1103/physrevb.55.1476

Cited by 238 publications

(120 citation statements)

References 14 publications

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“…Each powdered specimen was put in a plastic vial that showed no observable 59 Co NMR signal. The Knight shift in La x Co 4 Sb 12 was referred to the 59 Co resonance frequency of one molar of aqueous K 3 Co(CN) 6 at 71.386 MHz. This reference frequency gives rise to the 59 Co nuclear gyromagnetic ratio (γ n ) of 2π × 1.0102 × 10 3 Hz G −1 upon the application of a constant field, 7.0665 T.…”

Section: Methodsmentioning

confidence: 99%

Effect of partial La filling on the local electronic properties of La_xCo₄Sb₁₂studied using⁵⁹Co NMR

et al. 2008

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Abstract. We present a systematic investigation of the La x Co 4 Sb 12 skutterudites with x 0.2 using 59 Co nuclear magnetic resonance (NMR) spectroscopy. The NMR line shape, the quadrupole splitting, the Knight shift and the spin-lattice relation rate of each compound have been identified. For La x Co 4 Sb 12 , the central transition and the quadrupole linewidths increase with the La concentration because of the effect of the inhomogeneous electric field gradient. In addition, each linewidth exhibits a temperature-independent behavior, confirming the non-magnetic characteristic of these materials. The results of the isotropic Knight shift and the spin-lattice relaxation rate provide further information on the electronic structure around the Fermi surfaces of these compounds. In La 0.1 Co 4 Sb 12 and La 0.2 Co 4 Sb 12 , the low-temperature NMR relaxation rates follow the Korringa behavior, indicating a finite density of carriers at the Fermi level. The high-temperature relaxation rates go over to a semiconductor-like activated form, being consistent with a semimetallic response. A detailed analysis of the spin-lattice relaxation rate established that the partial Co 3d Fermi-level density of states (DOS) increases with the La content. The NMR observations were interpreted in terms of a two-band scenario that consists of predominant d-electron features at low temperatures and exotic behavior of s-character electrons at high temperatures. Moreover, the obtained Fermi-level DOS show good agreement with those observed from the electrical conductivity and the Seebeck coefficient measurements in these La-filled skutterudites.

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Section: Methodsmentioning

confidence: 99%

Effect of partial La filling on the local electronic properties of La_xCo₄Sb₁₂studied using⁵⁹Co NMR

et al. 2008

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“…Filled skutterudites were first synthesised by Jeitschko and Braun 123 and they became a target of intense scrutiny as TE materials in the late 1990s. [124][125][126] Compared with the conventional compounds with the chemical-bond homogeneity, the fillers possess much larger ADPs compared with the atoms forming the framework, leading to chemical-bond hierarchy and much reduced κ L . Nolas et al 127 found that the point defect scattering is not sufficient to explain the very low κ L in partially filled skutterudites.…”

Section: From the Conventional Phonon-phonon Interactions To Nanostrumentioning

confidence: 99%

On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

et al. 2016

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During the last two decades, we have witnessed great progress in research on thermoelectrics. There are two primary focuses. One is the fundamental understanding of electrical and thermal transport, enabled by the interplay of theory and experiment; the other is the substantial enhancement of the performance of various thermoelectric materials, through synergistic optimisation of those intercorrelated transport parameters. Here we review some of the successful strategies for tuning electrical and thermal transport. For electrical transport, we start from the classical but still very active strategy of tuning band degeneracy (or band convergence), then discuss the engineering of carrier scattering, and finally address the concept of conduction channels and conductive networks that emerge in complex thermoelectric materials. For thermal transport, we summarise the approaches for studying thermal transport based on phonon-phonon interactions valid for conventional solids, as well as some quantitative efforts for nanostructures. We also discuss the thermal transport in complex materials with chemical-bond hierarchy, in which a portion of the atoms (or subunits) are weakly bonded to the rest of the structure, leading to an intrinsic manifestation of part-crystalline part-liquid state at elevated temperatures. In this review, we provide a summary of achievements made in recent studies of thermoelectric transport properties, and demonstrate how they have led to improvements in thermoelectric performance by the integration of modern theory and experiment, and point out some challenges and possible directions. INTRODUCTION Thermoelectric (TE) materials are materials that can generate useful electric potentials when subjected to a temperature gradient (known as the Seebeck effect). Conversely, they also transfer heat against the temperature gradient when a current is driven against this potential (known as the Peltier effect). They are promising energy materials with many applications, such as waste heat harvesting, radioisotope TE power generation, and solid state Peltier refrigeration, all of which are driving growing research interest. A key challenge is to improve the TE properties in order to obtain more efficient energy conversion and in turn enable new practical applications. Good TE materials must have excellent electrical transport properties, measured by the TE power factor ( = S 2 σ, where S is the Seebeck coefficient and σ is the electrical conductivity), and also a very low thermal conductivity κ (composed of the electronic contribution κ e , the lattice contribution κ L , and the bipolar contribution κ bi ). Combining the two aspects gives us the dimensionless figure of merit ZT,

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“…Investigation on the thermoelectric properties in filled skutterudites has been initially started in 1990s. [2][3][4][5][6][7][8][9][10] Earlier studies are mainly focused on p-type Fe x Co 4Àx Sb 12 -based compounds and the values of the dimensionless thermoelectric figure of merit (ZT) had been reported above unity. 5,6,9,11,12 The progress in n-type filled skutterudites was rather slowly until partially filled skutterudites R y Co 4 Sb 12 with high filling fraction of the fillers were synthesized and reported with good thermoelectric performance at elevated temperature.…”

Section: Introductionmentioning

confidence: 99%

High-temperature electrical and thermal transport properties of fully filled skutterudites RFe4Sb12 (R = Ca, Sr, Ba, La, Ce, Pr, Nd, Eu, and Yb)

Qiu

Yang

Liu

et al. 2011

Journal of Applied Physics

162

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Fully filled skutterudites RFe 4 Sb 12 (R ¼ Ca, Sr, Ba, La, Ce, Pr, Nd, Eu, and Yb) have been prepared and the high-temperature electrical and thermal transport properties are investigated systematically. Lattice constants of RFe 4 Sb 12 increase almost linearly with increasing the ionic radii of the fillers, while the lattice expansion in filled structure is weakly influenced by the filler valence charge states. Using simple charge counting, the hole concentration in RFe 4 Sb 12 with divalent fillers (R ¼ Ca, Sr, Ba, Eu, and Yb) is much higher than that in RFe 4 Sb 12 with trivalent fillers (R ¼ La, Ce, Pr, and Nd), resulting in relatively high electrical conductivity and low Seebeck coefficient. It is also found that RFe 4 Sb 12 filled skutterudites having similar filler valence charge states exhibit comparable electrical conductivity and Seebeck coefficient, and the behavior of the temperature dependence, thereby leading to comparable power factor values in the temperature range from 300 to 800 K. All RFe 4 Sb 12 samples possess low lattice thermal conductivity. The correlation between the lattice thermal resistivity W L and ionic radii of the fillers is discussed and a good relationship of W L $ (r cage Àr ion ) 3 is observed in lanthanide metal filled skutterudites. CeFe 4 Sb 12 , PrFe 4 Sb 12, and NdFe 4 Sb 12 show the highest thermoelectric figure of merit around 0.87 at 750 K among all the filled skutterudites studied in this work.

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Low-temperature transport properties of the filled skutteruditesCeFe4−xCo

Cited by 238 publications

References 14 publications

Effect of partial La filling on the local electronic properties of La_xCo₄Sb₁₂studied using⁵⁹Co NMR

Effect of partial La filling on the local electronic properties of La_xCo₄Sb₁₂studied using⁵⁹Co NMR

On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

High-temperature electrical and thermal transport properties of fully filled skutterudites RFe4Sb12 (R = Ca, Sr, Ba, La, Ce, Pr, Nd, Eu, and Yb)

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Low-temperature transport properties of the filled skutteruditesCeFe4−xCo

Cited by 238 publications

References 14 publications

Effect of partial La filling on the local electronic properties of LaxCo4Sb12studied using59Co NMR

Effect of partial La filling on the local electronic properties of LaxCo4Sb12studied using59Co NMR

On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

High-temperature electrical and thermal transport properties of fully filled skutterudites RFe4Sb12 (R = Ca, Sr, Ba, La, Ce, Pr, Nd, Eu, and Yb)

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Effect of partial La filling on the local electronic properties of La_xCo₄Sb₁₂studied using⁵⁹Co NMR

Effect of partial La filling on the local electronic properties of La_xCo₄Sb₁₂studied using⁵⁹Co NMR