成果報告書詳細
管理番号20160000000423
タイトル*平成27年度中間年報 未利用熱エネルギーの革新的活用技術研究開発 熱電変換材料の技術シーズ発掘小規模研究開発 階層的構造制御によるチムニーラダー型熱電変換材料の高性能化
公開日2016/8/5
報告書年度2015 - 2015
委託先名国立大学法人東北大学大学院工学研究科
プロジェクト番号P15007
部署名省エネルギー部
和文要約
英文要約Title: Research and Development Project for Innovative Thermal Management Materials and Technologies. Incubation Research on Innovative Technologies in the Thermoelectric Materials. Development of chimney-ladder-type high performance thermoelectric materials through a multi-scaled structure control (FY2015-FY2016) FY2015 Annual Report

1. Preparation and detailed structure analysis of chimney-ladder phases
Prior to evaluate electronic structures, polycrystalline samples were prepared by arc melting method to construct a structure model for the first-principles calculation. Several heat treatment processes were performed to investigate the annealing effect on crystal structures. X-ray diffraction (XRD) was performed to identify phases prepared. The lattice parameters and chemical formula were determined using LeBail method by means of the XRD patterns. A discernible change in lattice parameters was observed for the as-cast (arc-melted) and melted (slowly cooled from the liquidus region) samples. In contrast, no practical change in the chemical formula was observed even if the nominal composition was significantly changed. Based on the results, a simple three dimensional crystal structure model has been constructed.
2. First-principles calculation of electronic structure and alloy designing
First-principles calculation was performed using the commercial application software based on the derived crystal structure model. Realistic thermoelectric (TE) performance was then evaluated using the BoltzTraP code. For several compounds, the Seebeck coefficient, electrical conductivity and thermal conductivity at high temperatures were computed based on the Boltzmann transport theory. Satisfactorily good TE performance was predicted for the Mn-Si based alloys, if we can control the electronic state and nano/micro structure of the silicides.
3. Preparation and TE properties of p-type materials
Several solid solutions were prepared and their power factor was measured. For a transition metal-substituted sample, the highest power factor, nearly close to the target value, was achieved.
4. Preparation and TE properties of n-type materials (to be started in FY2016)
5. Evaluation of phonon properties
A First-principles calculation software to compute phonon properties was installed in a workstation. After confirming the validity to obtain reasonable lattice thermal conductivity and Debye temperature in the well known compound, diamond and Mg2Si, similar calculations have been started in the target materials.
6. The effect of heat treatment on nano/micro structure
Annealing conditions (temperature, time and so on) to realize desirable nano/micro structure have been investigated. Characteristic XRD patterns which relate to realize a lower thermal conductivity was discovered.
In the forthcoming 2016FY, we will complete the project to simultaneously realize high TE power factor and extremely low thermal conductivity in the target material system.
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