Improved cryogenic thermoelectric performance of MgAgSb-based materials by modulation doping of Cu

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K22486
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0402:Nano/micro science, applied condensed matter physics, applied physics and engineering, and related fields
• Research Institution: Shibaura Institute of Technology
• Principal Investigator: Miao Lei 芝浦工業大学, 工学部, 教授 (60455540)
• Project Period (FY): 2020-09-11 – 2022-03-31
• Keywords: MgAgSb熱電材料 / 廃熱発電 / 放電プラズマ焼結 / 電気特性 / 熱伝導率制御 / ミクロ孔 / Cuドープ

Outline of Final Research Achievements

MgAgSb-based alloy was successfully prepared via ordinary planetary ball milling and spark plasma sintering. The element Cu successfully doped into MgAgSb to cooperatively optimize the electrical transport properties. The main parameters including nominal composition of raw powders Mg, Ag, Sb, Cu doping ratio, SPS pressure and heat treating conditions have been optimized. As a result, the maximum PF value of 2111 μW/mK-2 at 523K for MgAg0.93Cu0.02Sb0.98 was about 18% increased than 1788 μW/mK-2 for the initial sample MgAg0.95Sb0.98, and a peak ZT ~ 1.08 at 473 K were achieved for the sample MgAg0.935Cu0.015Sb0.98@ 60 MPa. In addition, we explored the phase composition and micro-pores effects and found that a large number of micro-pores can strengthen phonon scattering to reduce the lattice thermal conductivity. Thus, thermoelectric properties of MgAgSb-based alloys can be enhanced by Cu doping into Ag site and micro-pores structures.

Free Research Field

エネルギー材料

Academic Significance and Societal Importance of the Research Achievements

熱電発電ではエントロピーの高い低品位の低中温熱源（LNGや石炭を燃料とする火力発電所や様々な産業プロセスからの100℃以下の大量廃熱、冷熱産業や人体を含めた様々な環境周囲からの200K-常温範囲の未利用熱など）から、高品質の電気エネルギーに変換できる技術で、通常のRankine サイクル利用の熱水蒸気発電システムに比較して、可動部分を少なくし単純化できる発電プラント構成にできる等の優位性から、省エネルギー・地球温暖化問題に寄与できるために大きな期待がかかる。今回研究した熱電素子は ZT ~ 1.08 ＠473 Kに達し、その学術的意義は高く、上記応用分野に充分適用可能で社会的意義も高い。