Precious Measurement of Thermoelectric Performances of single crystals using AC Harman Method

2018 Fiscal Year Final Research Report

• Project/Area Number: 17H07399
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Single-year Grants
• Research Field: Inorganic materials/Physical properties
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: Okawa Kenjiro 国立研究開発法人産業技術総合研究所, 計量標準総合センター, 研究員 (80805119)
• Research Collaborator: AMAGAI Yasutaka
• Project Period (FY): 2017-08-25 – 2019-03-31
• Keywords: 熱電発電 / 精密計測 / 交流ハーマン法 / 熱電材料

Outline of Final Research Achievements

A method to obtain the zT is the Harman method, which can directly estimate zT through AC and DC voltage measurements using zT = (VDC -VAC / VAC). In the actual experiment, the estimated value of zT deviates from the ideal value because this formula is based on the assumption of an adiabatic condition. There have been only a few studies on the quantitative correction.
Here, in order to accurately determine zT using the Harman method, we performed thermal analysis using the heat conduction equation, which is based on the Fourier law. We developed the thermal correction using the one-dimensional heat conduction model, considered as heat losses of convection, Joule heating, Thomson heating, and conduction through lead wires. From this analysis, the temperature distribution in the sample was investigated. Our results indicate that a correction factor for each heat loss should be added to the original formula for highly accurate Harman measurement.

Free Research Field

固体物理、電気計測

Academic Significance and Societal Importance of the Research Achievements

未利用熱のうち300℃以下の低温域の未利用熱は膨大であり、産業分野のみで日本の年間総発電量を上回ると言われ、その積極的な利用が求められている。熱電発電技術は廃熱を直接電気エネルギーに変換する技術であり、産業界での潜在的なニーズは高く、省エネのため自動車部品やloT 用のセンサ電源への普及が進めば大きな波及効果が期待される。その一方で、熱電材料の評価には様々な測定手法が使われており統一された規格がない。本研究では、簡便な電気的評価法として有望な交流ハーマン法の高精度化に取り組んだ。正確な評価法の確立は、将来的な新材料の効率的な探索、信頼性評価、デバイスの効率評価応用へと繋がることが期待される。