Substitutions and dislocations enabled extraordinary n-type thermoelectric PbTe

Abstract

Substitutional point defects of aliovalent enable a significant manipulation in carrier concentration thus optimize the charge transport for an enhanced thermoelectric power factor, while dislocations induce strong lattice strain fluctuations for scattering phonons thus a reduced lattice thermal conductivity. With decades of development, both types of defects can be well controlled in conventional PbTe thermoelectrics, motivating the current work to focus on Gd-doping for increasing the electron concentration at a high mobility and on Cu2Te-alloying for creating dense in-grain dislocations for scattering phonons. Such a two-wheel driven approach, namely Gd-doping for a high power factor and Cu2Te-alloying for a low lattice thermal conductivity, eventually enables an extraordinary thermoelectric figure of merit, zT of ∼1.7 in n-type PbTe thermoelectrics.