Seebeck coefficient and resistivity measurement of polycrystalline Bi in a magnetic field

Seebeck coefficient and resistivity of a polycrystalline Bi sample were measured from 15 to 300 K in a magnetic field. The measured Seebeck coefficient at 15 K was -10 μV/K at 0 Tesla; however, the Seebeck coefficient enormously varied as a function of magnetic field and was over -1 mV/K at 1.5 Tesla. The Hall coefficient was measured by Van der Pauw method in order to evaluate the carrier density for estimating the mechanism of varying Seebeck coefficient at 15 K, and the carrier density decreased by a factor of 1/30 at 1.5 Tesla. It was shown that one reason for the variation of the Seebeck coefficient was the influence of phonon drag effect, even for polycrystalline Bi. A large Seebeck coefficient was observed below the Debye temperature of Bi in the magnetic field, The resistivity at 15 K also enormously increased in the transverse magnetic field due to the decreased carrier density, and the ratio of the increase of the resistivity compared to the case for no magnetic field was approximately 1000 times at 1.5 Tesla and decreased with increasing temperature. The increase in the resistivity influenced the phonon drag effect and increased the Seebeck coefficient.