Semiconductors and Thermoelectric Materials

Nolas, George S.; Yang, Jihui; Goldsmid, H. J.

doi:10.1007/0-387-26017-x_5

Cited by 7 publications

(7 citation statements)

References 75 publications

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“…This anisotropy ( κ a / κ c ~2) persists throughout the entire temperature-range of this study. The magnitude of the anisotropy is similar to that found for layered Bi 2 Te 3 242526 and higher than that of manganese silicide (HMS)27. While significant bonding anisotropy was held responsible for the anisotropic κ in Bi 2 Te 3 28 with van der Waals gaps in the low κ direction, a low-energy (<10 meV) twisting phonon and anisotropic group velocity of the optic phonons were found responsible for the observed κ anisotropy in HMS27.…”

Section: Resultssupporting

confidence: 69%

Optic phonons and anisotropic thermal conductivity in hexagonal Ge2Sb2Te5

Mukhopadhyay

Lindsay

Singh

2016

Sci Rep

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The lattice thermal conductivity (κ) of hexagonal Ge2Sb2Te5 (h-GST) is studied via direct first-principles calculations. We find significant intrinsic anisotropy (κa/κc~2) of κ in bulk h-GST, with the dominant contribution to κ from optic phonons, ~75%. This is extremely unusual as the acoustic phonon modes are the majority heat carriers in typical semiconductors and insulators. The anisotropy derives from varying bonding along different crystal directions, specifically from weak interlayer bonding along the c-axis, which gives anisotropic phonon dispersions. The phonon spectrum of h-GST has very dispersive optic branches with higher group velocities along the a-axis as compared to flat optic bands along the c-axis. The large optic mode contributions to the thermal conductivity in low-κ h-GST is unusual, and development of fundamental physical understanding of these contributions may be critical to better understanding of thermal conduction in other complex layered materials.

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Section: Resultssupporting

confidence: 69%

Optic phonons and anisotropic thermal conductivity in hexagonal Ge2Sb2Te5

Mukhopadhyay

Lindsay

Singh

2016

Sci Rep

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“…Isoelectronic substitution of the lower valent transition metal species has been studied for many years in TiNiSn-type compounds and has been used to optimize ZT in this class of materials via the introduction of alloy scattering. Such optimization, however, occurs typically over compositional ranges of tens of percents, suggesting a negligible impact of the 2% discrepancy observed in this study [22]. …”

Section: Phase and Compositional Analysiscontrasting

confidence: 51%

Introduction of resonant states and enhancement of thermoelectric properties in half-Heusler alloys

Simonson

Xie

et al. 2011

Phys. Rev. B

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“…More importantly, κ lat of the other samples decreases somewhat despite the decreased Yb filling fraction. Figure c clearly shows the abnormal behavior of Yb filling fraction dependent κ lat for x %Sb‐MS samples, in comparison with the results of Li et al and Tang et al It is generally assumed that guest fillers are loosely bonded with host Sb atoms of the Skutterudite framework and could effectively suppress the propagation of heat‐carrying phonons . However, our finding is in clear contradiction with the universally acknowledged truth that κ lat of filled Skutterudites is inversely proportional to the filling fraction .…”

Section: Resultssupporting

confidence: 63%

Grain Boundary Engineering for Achieving High Thermoelectric Performance in n‐Type Skutterudites

Meng

Liu

Cui

et al. 2017

Advanced Energy Materials

210

142

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Grain or phase boundaries play a critical role in the carrier and phonon transport in bulk thermoelectric materials. Previous investigations about controlling boundaries primarily focused on the reducing grain size or forming nanoinclusions. Herein, liquid phase compaction method is first used to fabricate the Yb‐filled CoSb3 with excess Sb content, which shows the typical feature of low‐angle grain boundaries with dense dislocation arrays. Seebeck coefficients show a dramatic increase via energy filtering effect through dislocation arrays with little deterioration on the carrier mobility, which significantly enhances the power factor over a broad temperature range with a high room‐temperature value around 47 μW cm−2 K−1. Simultaneously, the lattice thermal conductivity could be further suppressed via scattering phonons via dense dislocation scattering. As a result, the highest average figure of merit ZT of ≈1.08 from 300 to 850 K could be realized, comparable to the best reported result of single or triple‐filled Skutterudites. This work clearly points out that low‐angle grain boundaries fabricated by liquid phase compaction method could concurrently optimize the electrical and thermal transport properties leading to an obvious enhancement of both power factor and ZT.

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Semiconductors and Thermoelectric Materials

Cited by 7 publications

References 75 publications

Optic phonons and anisotropic thermal conductivity in hexagonal Ge2Sb2Te5

Optic phonons and anisotropic thermal conductivity in hexagonal Ge2Sb2Te5

Introduction of resonant states and enhancement of thermoelectric properties in half-Heusler alloys

Grain Boundary Engineering for Achieving High Thermoelectric Performance in n‐Type Skutterudites

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