Estimating the upper limit of the thermoelectric figure of merit in n- and p-type PbTe

Abstract

Lead Telluride-based materials are the best alloys for the fabrication of medium-temperature thermoelectric (TE) converters. Even if the outstanding TE performance has been already reported for the n- and p-type PbTe, it is still unknown the highest achievable limit of the figure of merit, that can be produced by this material. Considering the particularities of band structure and degenerate statistics of charge carriers, we calculated the dimensionless thermoelectric figure of merit ZT as a function of the chemical potential of electrons for n- and p-type PbTe. The lower bound estimate of ZTmax gives the value ZTmax ≈ 2 for n-PbTe and ZTmax ≈ 3 for p-PbTe. The model proposed considers the most probable scattering mechanisms in PbTe, such as scattering due to the deformation potential of acoustic (DA) and optical phonons (DO), polarization scattering due to optical phonons (PO), scattering due to the short-term potential of defects (SP), and scattering due to ionized impurity atoms (ID). The possibility of increasing the ZT parameter through the dominant scattering of carriers at the ionized impurities are analyzed. The optimal values of chemical potential μ required for the highest possible dimensionless thermoelectric figure of merit ZT are accurately determined for n- and p-type PbTe. This work says that the potential of PbTe as a thermoelectric material has not been fully realized yet and the ZT parameter for this material can be further enhanced beyond the reported experimental values.