Gigantic Phonon-Scattering Cross Section To Enhance Thermoelectric Performance in Bulk Crystals

Abstract

In thermoelectric energy conversions, thermal conductivity reduction is essential for enhancing thermoelectric performance while maintaining a high power factor. Herein, we propose an approach based on coated-grain structures to effectively reduce the thermal conductivity to a much greater degree when compared to that done by conventional nanodot nanocomposite. By incorporating CdTe coated layers on the surface of SnTe grains, the thermal conductivity is as low as 1.16 W/m-K at 929 K, resulting in a thermoelectric figure of merit, i.e., zT, of 1.90. According to our developed theory, phonons scatter coherently due to the phase lag between phonons passing through and around the coated grain. Such scattering is induced by the acoustic impedance mismatch between the coated layer and the grain, resulting in a gigantic phonon-scattering cross section. The phonon-scattering cross section of the coated grains is several orders of magnitude larger than that of the nanodots with the same impurity concentration. The power factor was also slightly increased by the energy filtering effect at the coated surface and additional minority carrier blocking by the heterointerfaces. This scheme can be utilized for various bulk crystals, meaning a broad range of materials can be considered for thermoelectric applications.

Te Nanoneedles Induced Entanglement and Thermoelectric Improvement of SnSe

“…The introduction of Te nanoneedles into the SnSe resulted in the formation of heterointerfaces between the Te and SnSe, which acted as effective phonon scattering centers. Thus, the κ values of the Te nanoneedles(x)/SnSe composites were lower than that of pristine SnSe, in accordance with the previous reports on the phonon scattering in composite materials [30][31][32]. The κ value of the pristine SnSe was restricted efficiently by the scattering of phonons at the heterointerfaces for reaction times of up to 4 h. With reaction times greater than 4 h, the κ value subsequently increased as the higher volumetric fraction of Te nanoneedles in the composite (Table S1) [26][27][28][29].…”

Employing Interfaces with Metavalently Bonded Materials for Phonon Scattering and Control of the Thermal Conductivity in TAGS‐x Thermoelectric Materials

“…Very recently, a novel approach has been introduced to realize a huge phonon scattering process by incorporating CdTe‐coated layers on the surface of SnTe grains. [ 36 ] The authors explained that such scattering is induced by the acoustic impedance mismatch between the CdTe‐coated layer and the SnTe grain. Interestingly, in all these examples the matrix is an MVB material, whereas the nanostructure is a non‐MVB material, more specifically a covalently bonded material.…”

Realizing High Thermoelectric Performance in Earth‐Abundant Bi2S3 Bulk Materials via Halogen Acid Modulation

“…[ 2 ] The above three parameters are intrinsically coupled; therefore, it is difficult to enhance these parameters simultaneously. Some effective strategies have been reported for enhancing TE properties, such as modulation doping, [ 3 ] band engineering, [ 4 ] nanostructuring, [ 5 ] grain boundary engineering, [ 3a,6 ] energy filtering, [ 7 ] compositing, [ 8 ] microstructure control. [ 9 ]…”