Seebeck coefficient and resistivity measurement of polycrystal Bi ina magnetic field

Y. Ishikawa¹, A.Suzuki², T. Komine³ , H. Shirai⁴, Y. Hasegawa¹

¹ Graduate School of Scienceand Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama338-8570, Japan

² Northern Laboratory, SaitamaIndustrial Technology Center, 2-133, Suehiro,Saitama 360-0031, Japan

³ Faculty ofEngineering, Ibaraki University, 4-12-1, Nakanarusawa, Hitachi-shi, Ibaraki316-8511, Japan

⁴ Faculty ofEngineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570,Japan

Seebeck coefficient andresistivity from 15 to 300K by using polycrystal Bi bulk were measured in amagnetic field from 0 to 4 Tesla. To improve the figure of merit, it isnecessary to enhance the Seebeck coefficient in the magnetic field. A purposeof this study is to investigate criterion between increasing and decreasing theSeebeck coefficient and how to enhance the Seebeck coefficient in the magneticfield. Measured Seebeck coefficient a(B) of aBi sample in the magnetic field enormously increased. The Seebeck coefficient a (0) at 0 Tesla was about–10µV/K at 15K, and observed over -1mV/K over 1.5 Tesla. NormalizedSeebeck coefficient a (B)/ a(0) was over a hundred times at 15K over 1.5 Tesla. On the other hand, theresistivity r(B) of the sample in themagnetic field also increased, and increasing ratio r(B)/ r (0) of the resistivitycompared with no magnetic field was about five thousand times at 15K and 4Tesla. The magnetic field dependence of the Seebeck coefficient and theresistivity was larger than that of any referenced values, and their increasingratios were decreased with increasing the temperature. Variation of the Seebeckcoefficient and the resistivity was especially prominent at low temperatureregion.