Jul 24, 2013
Endotaxial nanostructures and mass fluctuation drive up thermoelectric efficiency
Researchers in India have reported on the thermoelectric properties of PbSe0.5Te0.5: x (PbI2) from room temperature to 625 K. Thermoelectric materials are attracting attention thanks to their ability to recover waste heat and convert it into electricity.
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
About the author
Pankaj K Rawat is a PhD student at the Indian Institute of Technology in Kharagpur. Dr Biplab Paul was a post-doctoral student at the institute, and is now based at Linköping University in Sweden. P Banerji is a professor in the Materials Science Centre at the Indian Institute of Technology in Kharagpur.