Magnetic field effect forimprovement of thermoelectric conversion: a proposal for Nernst-Seebeck element

M. Hamabe¹, S.Yamamoto¹, H. Takahashi¹, S. Yamaguchi¹,H.Okumura², I. Yonenaga³,

T. Sasaki³, K.Watanabe³

¹Department of ElectricEngineering, Chubu University, Kasugai, Aichi, 487-8501, Japan

²Matsusaka University, Matsusaka,Mie, 515-8511, Japan

³Institute for MaterialResearch, Tohoku Univ. 2-1-1 Katayama, Aoba-ku, Sendai, Miyagi, 980-8577, Japan

Our proposal is to utilize themagnetic field in order to improve the figure of merit of the standardthermoelectric materials. Here, the following magnetic field effects are to beconsidered; (1) the variation of the Seebeck coefficient, (2) the presence ofthe Nernst voltage, (3) the increase of the magnetoresistance, and (4) thereduction of the thermal conductivity caused by the magnetic field. Thedirection of the Nernst electric field are perpendicular to that of the Seebeckelectric field. Hence, two small electrodes, located diagonally on therectangular specimen, can derive sum of the Nernst voltage and the Seebeckvoltage. We call this thermoelectric element as “the Nernst-Seebeck element”. We measured thethermoelectric properties of the square bismuth polycrystalline Nernst-Seebeckelement. The Nernst voltage achieved the same order to the Seebeck voltage forthe magnetic field of 1.5 T at the temperatures from 100 K to 290 K. Theestimated figure of merits of this bismuth Nernst-Seebeck element for 1.5 Tincreased for the all temperatures as compared for no magnetic field, in spiteof the increase of the magnetoresistance; especially for 150 K, 3.7 times ofthe increment of the figure of merit was achieved.