A Theoretical Model of Thermoelectric Transport Properties for Electrons and Phonons

A generic theoretical model for five bulk thermoelectric materials (PbTe, Bi 2 Te 3 , SnSe, Si 0.7 Ge 0.3 , and Mg 2 Si) has been developed based on the semiclassical model incorporating nonparabolicity, the two-band Kane model, the Hall factor, and the Debye–Callaway model for electrons and phonons. It is used to calculate thermoelectric transport properties, viz. the Seebeck coefficient, electrical conductivity, and electronic and lattice thermal conductivities, in the temperature range from room temperature up to 1200 K. The present model differs from others in the following regards: Firstly, thorough verification of modified electron scattering mechanisms is carried out by comparison with reported experimental data; Secondly, extensive verification of the model is presented, with concomitant agreement between calculations and reported measurements of effective masses, electron and hole concentrations, Seebeck coefficient, electrical conductivity, and electronic and lattice thermal conductivities; Thirdly, the present model provides the Fermi energy as a function of temperature and doping concentration; Fourthly, the velocities of sound are calculated using the Debye model rather than taken from literature. After verification of the present model, we were able to examine the recently attractive material SnSe, indicating a significant improvement in the dimensionless figure of merit.