成果報告書詳細
管理番号20110000001211
タイトル*平成22年度中間年報 ナノテク・先端部材実用化研究開発/カゴ状物質を利用したナノ構造制御高性能熱電変換材料の研究開発
公開日2011/9/9
報告書年度2010 - 2010
委託先名国立大学法人広島大学 国立大学法人山口大学 独立行政法人産業技術総合研究所 株式会社デンソー 株式会社KELK
プロジェクト番号P05023
部署名電子・材料・ナノテクノロジー部
和文要約和文要約等以下本編抜粋:1. 研究開発の内容及び成果等
カゴ状物質を利用したナノ構造制御高性能熱電変換材料の実用化を目指し、平成22年度は広島大学、山口大学、株式会社KELK、産業技術総合研究所、株式会社デンソーで共同研究を遂行した。平成22年度の具体的な成果を以下に示す。
研究開発項目 : (1)単結晶カゴ状物質による熱電材料高性能化の研究《広島大学》
(1)-1 カゴ状物質の熱伝導率の低減
VIII型クラスレートBa8Ga16Sn30(BGS)の熱伝導率をさらに低減する目的で、ゲストのBaをKで部分置換した単結晶を育成したところ、VIII型ではなくII型構造のものが得られた。元素組成分析と単結晶X線構造解析から、この新物質の化学式は(K,Ba)24(Ga,Sn)136と表され、ゲスト原子のKとBaはそれぞれ16面体と12面体に選択的に内包されていることが判った。室温で見積もられたZTは0.08とあまり高くないが、室温以上での熱電物性の評価が今後必要である。
英文要約The Hiroshima Univ. team synthesized single crystals of type-VIII Ba8Ga16-xCuxSn30 with n-type carriers from the Sn flux, whose thermoelectric (TE) figure of merits, ZT, reached 1.3 at 500 K. Ba8Ga16Sn30 crystals of 6 mm in diameter were grown by the vertical Bridgman method. The ZT values of n-type crystals are comparable with those grown by the flux method, while the ZT of p-type crystals is inferior.
The computational material design team of Yamaguchi Univ. and Denso Ltd., calculated the TE properties by the first-principles electronic structure calculation method. As for Sb-doped p-type samples, the ZT is found to be enhanced by the increase of the DOS in the valence band. The calculations also indicate that the low power factor of p-type sintered samples is caused by the defects of Ga atoms.
The experimental team of Yamaguchi Univ. prepared several types of sintered materials such as Sb- and Ge-doped Sn clathrates, type-III Sn clathrates, and mixed crystals of Sn and Ge clathrates. The TE power factor of p-type Ge-doped clathrates was improved drastically up to those of the n-type Sn clathrates. The Hall measurements of single and poly crystals of Sn clathrates revealed the significantly different transport properties between p-type and n-type samples. The Sn clathrate samples of large disk, 36mm in diam. and 9mm in thick., were successfully sintered by the spark-plasma-sintering method. The samples were supplied to the KELK Ltd. group to make TE elements.
The KELK team is preparing TE elements for fabricating a TEG module and try to form a barrier layer on BaGaSn materials. The team tested the tensile strength of the joints of low temperature thermosetting conductive adhesive. The experimental result was 15.7MPa, which is about a quarter of strength of adhesive company’s specifications. KELK will further optimize the joining conditions.
The AIST team fabricated a prototype of type-VIII clathrate / bismuth-telluride segmented TE module by using the high performance p-type and n-type bulk materials supplied by Yamaguchi Univ. A half-skeleton, eight-pair prototype module with the dimension of 28 × 28 × 5.7 mm3 was fabricated. The maximum output power and the efficiency were 1.6W and 4.5%, respectively, under the operating temperature difference of 300K between 303K and 603K.
DENSO Co., Ltd. designed the power generating basis unit(160W-class)composed of eight TE modules. In this demonstration unit, a modulated fin pitch structure was adopted in order to ease the temperature change along exhaust gas flow. For the temperature uniformity of ±30~C with 6mm pitch in upstream and 4mm in downstream, we calculated the heat transfer performance between TE module and heat exchanger. The performance is found to be enhanced compared to the conventional technology by inserting graphite layer and liquid metal between the interfaces.
ダウンロード成果報告書データベース(ユーザ登録必須)から、ダウンロードしてください。

▲トップに戻る