Configuring pnicogen rings in skutterudites for low phonon conductivity

Chi, Hang; Kim, Hyoungchul; Thomas, John; Su, Xianli; Stackhouse, Stephen; Kaviany, Massoud; Ven, Anton Van der; Tang, Xinfeng; Uher, Ctirad

doi:10.1103/physrevb.86.195209

Cited by 31 publications

(24 citation statements)

References 47 publications

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“…However, the ADP of chain B (B chain ) is twice that of icosahedral B (B pol and B eqt in B 13 C 2 and α-B 12 ). This large ADP of B chain atoms is one of distinct lattice behaviors of B 13 C 2 and we expect scattering of the heat-conducting phonon wave as in rattlers [34][35][36] . Such phonon dispersion and atomic displacement features in B 13 C 2 lattice are shown in Fig.…”

Section: A Lattice Dynamics and Polaron Formationmentioning

confidence: 99%

Coupled polaron-phonon effects on Seebeck coefficient and lattice conductivity of B13C2from first principles

Kim

Kaviany

2013

Phys. Rev. B

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Anomalous temperature-independent behavior of the Seebeck coefficient and lattice thermal conductivity of B13C2 are explained through polaron and phonon evolutions found using ab-initio molecular dynamics (AIMD). Analyses of lattice dynamics show that the unique icosahedron structures dominate the optical phonon modes and CBC inter-icosahedral bonds dominate the local acoustic vibration. We identify that the temperature-induced Jahn-Teller distortion and electron-phonon coupling in icosahedron structures create the small polarons (i.e., charge trapping and phonon softening). We also verify that large-displacement chain atoms scatter heat-conducting phonons. Using equilibrium and non-equilibrium AIMD methods (including entropy and energy analyses), we predict the Seebeck coefficient and its components, and the lattice thermal conductivity, and find good agreement with experiments. Softened and localized phonons make significant vibrational contribution to the Seebeck coefficient and allow for an amorphous-like lattice thermal conductivity.

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Section: A Lattice Dynamics and Polaron Formationmentioning

confidence: 99%

Coupled polaron-phonon effects on Seebeck coefficient and lattice conductivity of B13C2from first principles

Kim

Kaviany

2013

Phys. Rev. B

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“…Many measurements demonstrate the presence of a low lying optical phonon, supporting the point of view that the Ln ions undergo a low energy "rattling" behavior. 9,16 This low frequency rattling leads to strong effective phonon scattering and is responsible for the extremely low, nearly glass-like, thermal conductivity of these materials 8,[17][18][19][20][21] . Keppens et al 9 noted that there is a higher energy mode that involves Sb atoms in CeFe 4 Sb 12 , and theoretical calculations by Feldman et al 22 find low dispersion optic modes also associated with Sb at somewhat higher energies than the modes associated with the rattler atoms.…”

Section: Introductionmentioning

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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“…16 The bond anharmonicity serves as a measure of the deviation in lattice vibrations from a perfect harmonic motion and is characterized by the effective Grüneisen parameter. Generally, structures with a chemical bond hierarchy [17][18][19][20][21] and anisotropic multicenter bonding features 9 or those that possess a lone pair of electrons [22][23][24][25][26] exhibit a stronger anharmonicity. Therefore, the investigation of the chemical bonding, crystal structures and corresponding lattice dynamics is helpful in understanding phonon transport and the design of materials with an intrinsically low lattice thermal conductivity and high thermoelectric performance.…”

Section: Introductionmentioning

confidence: 99%

Intrinsically low thermal conductivity from a quasi-one-dimensional crystal structure and enhanced electrical conductivity network via Pb doping in SbCrSe3

et al. 2017

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The development of new routes for the production of thermoelectric materials with low-cost and high-performance characteristics has been one of the long-term strategies for saving and harvesting thermal energy. Herein, we report a new approach for improving thermoelectric properties by employing the intrinsically low thermal conductivity of a quasi-one-dimensional (quasi-1D) crystal structure and optimizing the power factor with aliovalent ion doping. As an example, we demonstrated that SbCrSe 3 , in which two parallel chains of CrSe 6 octahedra are linked by antimony atoms, possesses a quasi-1D property that resulted in an ultra-low thermal conductivity of 0.56 W m − 1 K − 1 at 900 K. After maximizing the power factor by Pb doping, the peak ZT value of the optimized Pb-doped sample reached 0.46 at 900 K, which is an enhancement of 24 times that of the parent SbCrSe 3 structure. The mechanisms that lead to low thermal conductivity derive from anharmonic phonons with the presence of the lone-pair electrons of Sb atoms and weak bonds between the CrSe 6 double chains. These results shed new light on the design of new and high-performance thermoelectric materials.

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Configuring pnicogen rings in skutterudites for low phonon conductivity

Cited by 31 publications

References 47 publications

Coupled polaron-phonon effects on Seebeck coefficient and lattice conductivity of B13C2from first principles

Coupled polaron-phonon effects on Seebeck coefficient and lattice conductivity of B13C2from first principles

Modeling correlated motion in filled skutterudites

Intrinsically low thermal conductivity from a quasi-one-dimensional crystal structure and enhanced electrical conductivity network via Pb doping in SbCrSe3

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