Lead-free SnTe-based thermoelectrics: enhancement of thermoelectric performance by doping with Gd/Ag

Zhang, Lijuan; Wang, Jianli; Cheng, Zhenxiang; Sun, Qiao; Li, Zhen; Dou, Shi Xue

doi:10.1039/c6ta01994c

Cited by 83 publications

(69 citation statements)

References 33 publications

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“…As compared to pristine SnTe, each of these two strategies enables a ≈150% zT enhancement, which accumulates to a ≈300% improvement when both are applied. The obtained peak zT of 1.6 (as shown in Figure a) is record for SnTe in p‐type, which is actually one of the highest among known p‐type thermoelectrics other than IV‐VI semiconductors (as shown in Figure b) . This work opens new possibilities for further improving this material, as well as promotes SnTe as an eco‐friendly solution for PbTe thermoelectrics in p‐type.…”

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confidence: 61%

Promoting SnTe as an Eco‐Friendly Solution for p‐PbTe Thermoelectric via Band Convergence and Interstitial Defects

et al. 2017

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Compared to commercially available p-type PbTe thermoelectrics, SnTe has a much bigger band offset between its two valence bands and a much higher lattice thermal conductivity, both of which limit its peak thermoelectric figure of merit, zT of only 0.4. Converging its valence bands or introducing resonant states is found to enhance the electronic properties, while nanostructuring or more recently introducing interstitial defects is found to reduce the lattice thermal conductivity. Even with an integration of some of the strategies above, existing efforts do not enable a peak zT exceeding 1.4 and usually involve Cd or Hg. In this work, a combination of band convergence and interstitial defects, each of which enables a ≈150% increase in the peak zT, successfully accumulates the zT enhancements to be ≈300% (zT up to 1.6) without involving any toxic elements. This opens new possibilities for further improvements and promotes SnTe as an environment-friendly solution for conventional p-PbTe thermoelectrics.

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confidence: 61%

Promoting SnTe as an Eco‐Friendly Solution for p‐PbTe Thermoelectric via Band Convergence and Interstitial Defects

et al. 2017

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“…It has already been reported that Bi substitution in GeTe solid state solutions can result in segregation of Bi-rich nanoprecipitates [39]. In addition, such types of inclusions can cause collective phonon scattering from nanoprecipitates, meso-structured grain boundaries, and other crystallographic defects that could pave the way for reduction in lattice thermal conductivity [7,49,52]. In this work, for heavily-doped GTS-Bi samples, an ultra-low lattice thermal conductivity of ~0.7 Wm −1 K −1 was achieved at 523 K.

κ_{t o t a l}

obtained for these doped crystalline materials; especially, the Bi-doped ones are essentially in the range with the

κ_{t o t a l}

values of some of the well-known effective thermoelectric materials [15,42,49,53,54,55,56,57].…”

Section: Resultsmentioning

confidence: 99%

Thermoelectric Properties of Highly-Crystallized Ge-Te-Se Glasses Doped with Cu/Bi

et al. 2017

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Chalcogenide semiconducting systems are of growing interest for mid-temperature range (~500 K) thermoelectric applications. In this work, Ge20Te77Se3 glasses were intentionally crystallized by doping with Cu and Bi. These effectively-crystallized materials of composition (Ge20Te77Se3)100−xMx (M = Cu or Bi; x = 5, 10, 15), obtained by vacuum-melting and quenching techniques, were found to have multiple crystalline phases and exhibit increased electrical conductivity due to excess hole concentration. These materials also have ultra-low thermal conductivity, especially the heavily-doped (Ge20Te77Se3)100−xBix (x = 10, 15) samples, which possess lattice thermal conductivity of ~0.7 Wm−1 K−1 at 525 K due to the assumable formation of nano-precipitates rich in Bi, which are effective phonon scatterers. Owing to their high metallic behavior, Cu-doped samples did not manifest as low thermal conductivity as Bi-doped samples. The exceptionally low thermal conductivity of the Bi-doped materials did not, alone, significantly enhance the thermoelectric figure of merit, zT. The attempt to improve the thermoelectric properties by crystallizing the chalcogenide glass compositions by excess doping did not yield power factors comparable with the state of the art thermoelectric materials, as these highly electrically conductive crystallized materials could not retain the characteristic high Seebeck coefficient values of semiconducting telluride glasses.

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“…Recent reports have demonstrated that the optimal maximum temperature for investigating the thermal and thermoelectric properties of SnSe is around 800 K due to the presence of the visible and invisible microgaps along the cleavage plane in the specimen arising from the shrinkage of the unit cell over 800 K caused by the phase transition. [27][28][29] In our work, L is calculated from the equation L = 1.5 + exp [−|α|/116], where L is in 10 −8 W Ω K −2 and α in µV K −1 . The total thermal conductivity is composed of the electronic thermal conductivity (κ ele ) and the lattice thermal conductivity (κ lat ).…”

Section: Thermoelectric Properties Of Pristine Ag-and Sncl 2 -Doped mentioning

confidence: 99%

Three‐Stage Inter‐Orthorhombic Evolution and High Thermoelectric Performance in Ag‐Doped Nanolaminar SnSe Polycrystals

Zhang

Wang

Sun

et al. 2017

Advanced Energy Materials

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generation in deep-space and waste heat recovery from vehicle exhaust, as well as ice-free refrigeration in wine-storage cabinets, hotel room mini-refrigerators, and office water coolers. [1][2][3][4][5] The performance of TE materials is determined by the dimensionless figure of merit (ZT), defined as ZT = α 2 σT/(κ lat + κ ele ), where α, σ, κ lat , κ ele , and T are the Seebeck coefficient, electrical conductivity, lattice thermal conductivity, electronic thermal conductivity, and absolute temperature, respectively. The conversion efficiency for these potential applications requires high ZT over a wide range of temperatures. [6] For effective waste heat recovery in vehicles under a 350 K temperature differential, the average or device ZT (ZT dev ) should be about 1.25 in order to increase mileage up to 10%, [1,7] while for primary power generation, an average ZT of more than 1.5 is required under an 800 K temperature differential. [1,7] Recently, SnSe single crystals have produced a surge in the field of thermoelectrics as a new type of promising TE materials because of the intrinsically ultralow thermal conductivity (<0.4 W m −1 K −1 at 923 K) and high ZT along the b-and c-crystallographic directions (>2.3 at 923 K). [8] A new record of ZT dev ≈ 1.34 from 300-773 K along the b-crystallographic direction was achieved in thermoelectric device fabricated from hole-doped SnSe single crystal. [9] Nevertheless, the difficulties in large-scale synthesis of single crystals limit their practical applications, and extensive efforts have been devoted to the fabrication of high-performance polycrystalline counterparts. [10][11][12][13][14][15] For example, Wei et al. [12] reported a ZT of ≈0.8 at 800 K in 1% Na-and K-doped SnSe, which was produced by conventional solid state reaction followed by a spark plasma sintering (SPS) treatment. Due to an impressively low lattice thermal conductivity (≈0.20 W m −1 K −1 at 773 K) arising from the presence of coherent nanoprecipitates in the SnSe matrix, a high ZT of ≈1.1 at 773 K was achieved in the direction perpendicular to the pressing direction of SPS for ball-milled K-doped SnSe. [11] Apart from p-type alkali dopants (Li, Na, K), n-type dopants such as I and BiCl 3 are also adopted to improve the performance of polycrystalline SnSe. [14,16] For instance, a ZT of ≈0.8 at 773 K was obtained in I-doped SnSe polycrystals, whichThe ultrahigh thermoelectric performance of SnSe-based single crystals has attracted considerable interest in their polycrystalline counterparts. However, the temperature-dependent structural transition in SnSe-based thermoelectric materials and its relationship with their thermoelectric performance are not fully investigated and understood. In this work, nanolaminar SnSe polycrystals are prepared and characterized in situ using neutron and synchrotron powder diffraction measurements at various temperatures. Rietveld refinement results indicate that there is a complete inter-orthorhombic evolution from Pnma to Cmcm by a series of layer slips and stretches a...

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Lead-free SnTe-based thermoelectrics: enhancement of thermoelectric performance by doping with Gd/Ag

Cited by 83 publications

References 33 publications

Promoting SnTe as an Eco‐Friendly Solution for p‐PbTe Thermoelectric via Band Convergence and Interstitial Defects

Promoting SnTe as an Eco‐Friendly Solution for p‐PbTe Thermoelectric via Band Convergence and Interstitial Defects

Thermoelectric Properties of Highly-Crystallized Ge-Te-Se Glasses Doped with Cu/Bi

Three‐Stage Inter‐Orthorhombic Evolution and High Thermoelectric Performance in Ag‐Doped Nanolaminar SnSe Polycrystals

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