Evaluation of the Improvement in the Figure of Merit of Bi_2Te_3-Based Alloys with Addition of Ultrafine Scattering Centers

The addition of ultrafine scattering centers into Bi_2Te_3-based materials and their impact on the thermal and electrical transport properties in a 200-500 K temperature range are discussed. Based on previous theoretical efforts, the resulting improvements in the figure of merit of these heavily doped thermoelectric semiconductors were calculated as a function of composition, temperature, doping level, particulate size and concentration. Determination of the lattice thermal conductivity of the various alloys was conducted by considering phonon-phonon, carrier-phonon, point defect and inert scattering center scattering mechanisms. Degradation of the electrical properties due to the increase scattering rate was also taken into account. Practical application of these results is considered.