Structural Modifications Induced by Sodium Doping in PbTe Thermoelectric Materials Prepared by Low Temperature Synthesis

Abstract

In the current study, the effect of a Low Temperature Synthesis (LTS) and sodium doping on the structural properties of PbTe materials is investigated using high resolution transmission electron microscopy and image analysis methods. The LTS technique results into nanoscale particles for PbTe, whose size is further reduced by the subsequent Na doping. Increasing the dopant loading brings upon nanoscale precipitates into the PbTe particles, which are Na-rich and occasionally coherently incorporated inside the host matrix. A substantial amount of residual strain was detected inside PbTe particles and at grain boundaries, which plays a key role in the reduction of its thermal conductivity. The structural modifications induced by dopant element and LTS results in a significant enhancement of the PbTe thermoelectric efficiency, exhibiting ZT values up to 1.36 at 720 K for the 2 at% Na-doped sample. This enhanced thermoelectric performance, along with the low-cost LTS method is proved to be highly advantageous, since it enables to scale up the production of high ZT materials much more easily and inexpensively.",