Multi‐Scale Microstructural Thermoelectric Materials: Transport Behavior, Non‐Equilibrium Preparation, and Applications

Abstract

Considering only about one third of the world's energy consumption is effectively utilized for functional uses, and the remaining is dissipated as waste heat, thermoelectric (TE) materials, which offer a direct and clean thermal-to-electric conversion pathway, have generated a tremendous worldwide interest. The last two decades have witnessed a remarkable development in TE materials. This Review summarizes the efforts devoted to the study of non-equilibrium synthesis of TE materials with multi-scale structures, their transport behavior, and areas of applications. Studies that work towards the ultimate goal of developing highly efficient TE materials possessing multi-scale architectures are highlighted, encompassing the optimization of TE performance via engineering the structures with different dimensional aspects spanning from the atomic and molecular scales, to nanometer sizes, and to the mesoscale. In consideration of the practical applications of high-performance TE materials, the non-equilibrium approaches offer a fast and controllable fabrication of multi-scale microstructures, and their scale up to industrial-size manufacturing is emphasized here. Finally, the design of two integrated power generating TE systems are described-a solar thermoelectric-photovoltaic hybrid system and a vehicle waste heat harvesting system-that represent perhaps the most important applications of thermoelectricity in the energy conversion area.

Promising Thermoelectric Bulk Materials with 2D Structures

“…While the phonon MFP in SnSe is quite short, [98] the scattering mechanism is most likely partially specular and partially dif fuse. Therefore, the Se interstitials and Sn vacancies, which increase the atomic scale roughness, can cause a reduction in the specular parameter according to Equation (2). The specular parameter is also wavelength dependent.…”

Thermoelectric performance of CuFeS2+2x composites prepared by rapid thermal explosion

“…One of the most exciting clean energy conversion technologies is thermoelectricity that can be used to harvest waste industrial heat via the Seebeck effect and convert it into electricity using a purely solid-state means without moving parts [1][2][3][4][5] . The efficiency of the conversion process is determined by the dimensionless figure of merit ZT = α 2 σT /(κ e +κ L ), where α is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ e and κ L are the electronic and lattice contributions, respectively, to the thermal conductivity [6][7][8][9][10][11] . Basically, a good thermoelectric material should have both a high Seebeck coefficient and electrical conductivity, and possess as low a thermal conductivity as possible.…”

Superstrengthening Bi2Te3 through Nanotwinning

“…However, under severe operation conditions, TE materials suffer from unavoidable thermomechanical stresses from cycling of the temperature gradients, leading to rapid deterioration of material performance and accelerated failure of TE devices [5][6][7]. In order for thermoelectrics to play a significant role in engineering applications to alternative energy, the strength and the toughness must be dramatically enhanced.Industrial low temperature waste heat accounts for almost one-third of total energy consumption [8]. The bismuth telluride (Bi 2 Te 3 ) state-of-the-art TE material has been widely used for TE refrigeration in this temperature range (300-550 K) [9], and is now being considered in the automotive industry for recovering waste heat from exhaust systems.…”

“…Industrial low temperature waste heat accounts for almost one-third of total energy consumption [8]. The bismuth telluride (Bi 2 Te 3 ) state-of-the-art TE material has been widely used for TE refrigeration in this temperature range (300-550 K) [9], and is now being considered in the automotive industry for recovering waste heat from exhaust systems.…”