Basic approach to thermoelectric materials

The effects of the method of fabricating thermoelecteric materials. such as sintering or direct fabrication, have been the focus of recent attention. The low-dimensional materials sush as two-dimensional film or skutterudite structure has been made use of recently in the higher performance. A comput er simulation by DV-X alpha calculation using the molecular orbital method was carried out to investigate the electronic structures related to the the rmoelectric properties such as electrical conductivity and the Seebeck coef ficient of FeSi2. As regards electrical conductivity, the energy gap was es timated to be 0.53 eV when conventional HOMO and LUMO levels were considere d. On the other hand, a new definition was provided for the Seebeck coeffic ient: it is the energy difference between HOMO and LUMO levels which have t he same symmetry at the twofolded- and threefolded-degenerated energy struc tures. Furthermore, computer simulation and experiment gave the same trends concerning the thermoelectric properties of metal-added materials.