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Ultralow Lattice Thermal Conductivity and Enhanced Thermoelectric Performance in SnTe:Ga Materials
Al Rahal Al Orabi, Rabih,Hwang, Junphil,Lin, Chan-Chieh,Gautier, Ré,gis,Fontaine, Bruno,Kim, Woochul,Rhyee, Jong-Soo,Wee, Daehyun,Fornari, Marco American Chemical Society 2017 Chemistry of materials Vol.29 No.2
<P>Ultralow thermal conductivity is of great interest in a variety of fields, including thermoelectric energy conversion. We report, for the first time, experimental evidence that Ga-doping in SnTe may lower the lattice thermal conduction slightly below the theoretical amorphous minimum at high temperature. Such an effect is justified by the spontaneous formation of nanoprecipitates we characterized as GaTe. Remarkably, the introduction of Ga (2-10%) in SnTe also improves the electronic transport properties by activating several hole pockets in the multivalley valence band. Experimental results are supported by density functional theory calculations. The thermoelectric figure of merit, ZT, reaches similar to 1 at 873 K in Sn0.96Ga0.07Te, which corresponds to an similar to 80% improvement with respect to pure SnTe.</P>
제일 계산 기법을 이용한 백철광계 FeAs₂ 열전재료 특성 연구
방세미(Semi Bang),Rabih Al Rahal Al Orabi,손지현(Ji-Hyun Son),김현아(Hyeon A Kim),김동민(Dong-Min Kim),원동희(Dong-Hee Won),김지수(Ji-Su Kim),위대현(Daehyun Wee) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
There are significant demands for thermoelectric materials that can be used for environment-friendly cooling applications that need to be met. A few recent studies reported thermoelectric properties of the FeAs₂ marcasite compound, which has a potential for becoming a good thermoelectric material for low-temperature cooling applications. The compound can be more environment-friendly and more economically viable than other competing materials, for the composition does not involve rare and expensive element like Te or Pt. In this study, we investigate thermoelectric properties of the FeAs₂ marcasite compound by first-principles calculations in order to investigate the feasibility for the use in practical cooling applications. Electronic band structures and density of states are constructed from DFT (density functional theory) calculations, from which electrical properties, including the Seebeck coefficient and the electrical conductivity, are estimated. In addition, vibrational characteristics are investigated through DFPT (density functional perturbation theory) calculations.
Ginting, Dianta,Lin, Chan-Chieh,Lydia, R.,So, Hyeon Seob,Lee, Hosun,Hwang, Junpil,Kim, Woochul,Al Rahal Al Orabi, Rabih,Rhyee, Jong-Soo Elsevier 2017 Acta materialia Vol.131 No.-
<P>Lead chalcogenides have long been studied as promising thermoelectric materials, operating at the mid temperature range of 500-950 K. Here, we studied thermoelectric properties of pseudo-quaternary compounds of (PbTe)(0.95-x)(PbSe)(x)(PbS)(0.05) (x = 0.0, 0.05, 0.10, 0.15, 0.20, 035, and 0.95) with 1% Nadoping, synthesized by melting and rapid quenching of pristine compounds of PbTe, PbSe, and PbS and followed by hot press sintering. The lattice parameters and transmission electron microscopy confirmed that the PbSe makes solid solution with PbTe leading to PbTe1-xSex matrix while the PbS precipitates in the matrix. In terms of two valence bands model, the energy band gap between conduction and valence L-band was decreased and the energy difference between L-and E-bands was increased with increasing Se concentration. The band convergence at high temperature may be associated with the enhancement of power factor. The PbS nano-scale precipitation in the matrix attributed to the decrease of lattice thermal conductivity. From the Matthiessen's rule, the lattice thermal conductivity was described by the nano precipitation as well as alloy scattering of phonons. The simultaneous emergence of band convergence and nano-precipitation in the quaternary compounds of (PbTe)(0.95-X)(PbSe)(x)(PbS)(0.05) gives rise to exceptionally high zT value of 23 at 800 K for x = 0.20. The high zT value also showed enhancement of practical thermoelectric performances such as engineering zT(eng), device efficiency eta, output power density P-d, and device zT(d). In addition, high zT compounds have good compatibility with the n-type I-doped PbTe compound, which can be applied to practical waste heat power generation. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.</P>