The role of nanostructuring strategies in PbTe on enhancing thermoelectric efficiency

Abstract

A nanostructured n-type thermoelectric (TE) material based on lead telluride (PbTe) (doped with 0.2 wt% PbI2 and 0.3 wt% Ni) was fabricated and investigated. Fabricating technology included the synthesis of PbTe by direct alloying of components, the grinding of synthesized PbTe in a planetary ball mill, and the compaction of the nanopowders by spark plasma sintering (SPS). Complex investigations of the structure and composition of powders and nanostructured PbTe and the thermoelectric parameters of nanostructured PbTe were carried out. The particle sizes of the powders ground for 20 and 60 min varied from 36 to 378 nm and from 29 to 210 nm, respectively. The maximum value of dimensionless thermoelectric figure of merit (ZT) = 1.35 for nanostructured PbTe was obtained for a sample compacted by SPS after grinding synthesized PbTe for 60 min, which is 14% higher than ZT for TE material obtained by hot pressing. Recrystallization of crystalline particles during SPS leads to an increase of the grain sizes in nanostructured PbTe by approximately 3 times and the elimination of microdeformations that appear during grinding. Analysis of the temperature dependencies of thermoelectric parameters showed that an increase in ZT for nanostructured PbTe is achieved due to the decrease in lattice thermal conductivity.