Effect of Powder ALD Interface Modification on the Thermoelectric Performance of Bismuth

Abstract

In thermoelectric materials, phase boundaries are crucial for carrier/phonon transport. Manipulation of carrier and phonon scatterings by introducing continuous interface modification has been shown to improve thermoelectric performance. In this paper, a strategy of interface modification based on powder atomic layer deposition (PALD) is introduced to accurately control and modify the phase boundary of pure bismuth. Ultrathin layers of Al2O3, TiO2, and ZnO are deposited on Bi powder by typically 1–20 cycles. All of the oxide layers significantly alter the microstructure and suppressed grain growth. These hierarchical interface modifications aid in the formation of an energy barrier by the oxide layer, resulting in a substantial increase in the Seebeck coefficient that is superior to that of most pure polycrystalline metals. Conversely, taking advantage of the strong electron and phonon scattering, an exceptionally large decrease in thermal conductivity is obtained. A maximum figure of merit, zT, of 0.15 at 393 K and an average zT of 0.14 at 300–453 K were achieved in 5 cycles of Al2O3‐coated Bi. The ALD‐based approach, as a practical interfacial modification technique, can be easily applied to other thermoelectric materials, which can contribute to the development of high‐performance thermoelectric materials of great significance.

Surface Modification of Bismuth by ALD of Antimony Oxide for Suppressing Lattice Thermal Conductivity

“…The observed transition from transgranular to intergranular fracture mode demonstrates the strong influence of surface modification on the morphology and grain growth of sintered Bi particles, mostly suppressing the Bi grain size (Figure b–f). Similar behavior was observed where TiO 2 coatings were applied on Bi particles . The particle size distribution histogram shows an average grain size of 1.4 μm for Bi coated with 5 cycles of Sb 2 O 5 (Figure S2).…”

“…Atomic layer deposition (ALD) is well-known as an advanced layer-by-layer deposition method for its ability to manufacture exceedingly homogeneous films in a controlled manner . Furthermore, controlled layer-by-layer growth might ensure homogeneous deposition from a planar substrate to a three-dimensional structure and give a fresh insight into the deposition of thin films on the surface of powders . Powder ALD (PALD) has been used effectively in a variety of traditional TE materials systems, such as Bi 2 Te 3 alloys, − CoSb 3 , and ZrNiSn-based materials .…”

“…Powder ALD (PALD) has been used effectively in a variety of traditional TE materials systems, such as Bi 2 Te 3 alloys, − CoSb 3 , and ZrNiSn-based materials . In all these investigations, the values of κ tot were unprecedentedly suppressed using TiO 2 /Al 2 O 3 /ZnO coating layers because of their brilliant chemical stability and developed deposition process. ,,,, However, if further suppression of κ tot in TE matrices is desired, one of the main challenges that must be addressed is the development of novel coating layers.…”

“…(a) Temperature dependence of κ tot , (b) κ tot of Sb 2 O 5 –Bi sample with Sb-doped Bi single crystals and polycrystals, − ,− (c) temperature dependence of κ lat of Bi coated with different ALD cycles of Sb 2 O 5 , (d) Δ κ lat / κ lat–Bi of Sb 2 O 5 -coated Bi compared to that of Al 2 O 3 -, TiO 2 -, and ZnO-coated Bi. (e) 1/ κ lat vs calculated R K for Al 2 O 3 - , TiO 2 -, ZnO-, and Sb 2 O 5 - coated Bi samples at 300 K …”

Improving the thermoelectric performance of ZrNi(In,Sb)-based double half-Heusler compounds

“…S4(a)†). 30 κ L shows a decrease from 2.22 W m −1 K −1 to 0.98 W m −1 K −1 at 973 K with a shrinking In/Sb ratio. Apparently, κ e dominates the heat conduction, suggesting the importance of reducing the carrier concentration for a lower κ tot .…”