PbTe is the most studied thermoelectric chalcogen and holds the best performance for power-generation applications in the mid-temperature range (500–900 K). However, tellurium is extremely rare in the Earth's crust (0.001 ppm), and this will eventually limit the thermoelectric applications of such Te-based materials. Therefore, the development of high-performance thermoelectric materials without tellurium or with low tellurium content is very important.

For effective thermoelectric power generation, the thermal conductivity of a material must be reduced below the alloy limit without affecting the other interconnected thermoelectric transport parameters, especially the electrical conductivity, which can be challenging in practice. It has been found that the combined effect of embedded band-aligned endotaxial nanostructures together with atomic mass fluctuations can decouple these thermoelectric parameters and allow the performance of the material to be upgraded.

In the study, the team based at the Materials Science Centre, Indian Institute of Technology in Kharagpur, has shown experimentally that the crystallographic planes (see image), the conduction bands of the host matrix, PbSe0.5Te0.5, and the embedded nanostructures (PbTe/PbSe) are completely aligned to each other, which facilitates the scattering-free transport of charge carriers, simultaneously blocking the transport of long-wavelength phonons. The mass fluctuation further reduces the thermal conductivity by scattering the short-wavelength phonons.

This scattering-free charge transport with enhanced phonon scattering enables high thermoelectric efficiency in the material system, and this approach could also be helpful in maximizing the figure-of-merit of other state-of-the-art thermoelectric materials.

Full details can be found in the journal Nanotechnology 24 215401

Further reading

Thermoelectrics go nano (Mar 2008)
Nanostructuring boosts thermoelectric power in semiconductor layers (Oct 2009)
Nanoparticles boost thermoelectric efficiency (Jan 2011)