Electronic Transports for Thermoelectric Applications on IV–VI Semiconductors

Abstract

Seebeck effect, Peltier effect, Thomson effect, electronic thermal conductivity, Hall effect, and Nernst effect are described on the basis of electronic conduction theory, taking account of effective mass anisotropy, nonparabolicity in Ek relation, and temperature dependent band gap. It is shown that the temperature dependence of the band gap does not modify the basic equations for the Seebeck coefficient, thermal conductivity, and Nernst coefficient. In narrow gap semiconductors, existence of minority carriers significantly enhances the electronic thermal conductivity, owing to the multiple carrier transport known as bipolar diffusion. Calibration coefficient £ for the Hall effect (R H ¼ À£=en) is increased by nonparabolicity in the Ek relation. Nernst coefficient gives useful information on scattering properties of the materials.

Strong temperature dependence of the Hall factor of p-type CoSb3: A re-analysis incorporating band nonparabolicity

“…Ishida et al 23 pointed out that the Hall factor for free electrons in PbTe is increased due to the nonparabolicity of the conduction band. However, the calculated increase with respect to the parabolic band was only 40% even when assuming a scattering parameter of r ¼ 0.…”

Thermoelectric conversion efficiency in IV-VI semiconductors with reduced thermal conductivity

“…Detail calculations of the Seebeck coefficient and carrier thermal conductivity are described in previous papers. [12][13][14] The direct bandgaps of PbS and PbTe are 410 and 320 meV at 300K, respectively, and the bandgaps increase by 0.5meV/K with the temperature. In the calculation, we assumed a density of states effective mass 0.125m 0 for each L-point valleys of both conduction and valence bands in PbS, and 0.089m 0 for each L-point valleys in PbTe at 300K.…”

“…Under Boltzmann transport theory, electrical conductivity σ and Seebeck coefficient S are given by 12,13 …”

“…Infrared radiation also affects the thermal conduction, but this effect is ignored in this discussion. The carrier thermal conductivity is calculated under the Boltzmann transport framework and given in the form 13,14 :…”