Nanostructured Thermoelectrics
Thermoelectric materials are capable to directly interconvert the thermal energy and electricity, being thus considered a promising candidate for the sustainable energy production with carbon-free emission. The Achilles heel which limits a broad application of thermoelectric technology is its low conversion efficiency. The thermoelectric conversion efficiency is generally determined by the dimensionless figure of merit, ZT, expressed as:
\(ZT = \frac{S^2\sigma T}{k_e + k_l}\)
where S is the Seebeck coefficient, the electrical conductivity, T the temperature, the electronic thermal conductivity, and the lattice thermal conductivity, which is the only one that can be independently modified. Thus, reducing the lattice thermal conductivity by introducing nanostructures has attracted intensive attention in last decades.
In “Atomprobe” group we are investigating these nanostructures using our unique expertise namely correlative microscopy, i.e. combination of atom probe tomography (APT) with transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD). The configuration of nanostructures can be characterized by TEM and EBSD, while the chemical composition at nanometer scale is in practical very difficult to determine by EDX or EELS. Therefore, APT has an unique ability to measure the chemical composition of nanostructures at the nanoscale and in 3D. Our overall goal is to understand the correlation between the structure, composition, and thermo-electrical properties by correlating the TEM, EBSD, and APT obtained on the same location on the sample. These findings will guide us to judiciously design novel thermoelectric materials with high thermoelectric performance, as illustrated in the figure below.