Correction: Thermoelectric nanowires for dense 3D printed architectures.

Correction for 'Thermoelectric nanowires for dense 3D printed architectures' by Danwei Zhang et al., Mater. Horiz., 2024, 11, 847-854, https://doi.org/10.1039/D3MH01646C.

Synergistic Combination of Sb2Si2Te6 Additives for Enhanced Average ZT and Single-Leg Device Efficiency of Bi0.4Sb1.6Te3-based Composites.

Thermoelectric materials are highly promising for waste heat harvesting. Although thermoelectric materials research has expanded over the years, bismuth telluride-based alloys are still the best for near-room-temperature applications. In this work, a ≈38% enhancement of the average ZT (300-473 K) to 1.21 is achieved by mixing Bi0.4Sb1.6Te3 with an emerging thermoelectric material Sb2Si2Te6, which is significantly higher than that of most BiySb2-yTe3-based composites. This enhancement is facilitated by the unique interface region between the Bi0.4Sb1.6Te3 matrix and Sb2Si2Te6-based precipitates with an orderly atomic arrangement, which promotes the transport of charge carriers with minimal scattering, overcoming a common factor that is limiting ZT enhancement in such composites. At the same time, high-density dislocations in the same region can effectively scatter the phonons, decoupling the electron-phonon transport. This results in a ≈56% enhancement of the thermoelectric quality factor at 373 K, from 0.41 for the pristine sample to 0.64 for the composite sample. A single-leg device is fabricated with a high efficiency of 5.4% at ΔT = 164 K further demonstrating the efficacy of the Sb2Si2Te6 compositing strategy and the importance of the precipitate-matrix interface microstructure in improving the performance of materials for relatively low-temperature applications.

Thermoelectric nanowires for dense 3D printed architectures.

The large-scale employment of 3D printed inorganic thermoelectrics is primarily constrained because of their lower efficiencies as compared to those fabricated from conventional methods such as spark plasma sintering and hot-pressing. This originates from the significant challenge in the densification of printed parts, particularly through the direct-ink-writing fabrication process, which demands a high binder content for printability. To achieve high-density printed thermoelectrics, the ink formulation process often involves the addition of substantial filler content and sintering aids, coupled with prolonged sintering periods. Here, we propose a strategy to resolve the low densification issue of 3D printed thermoelectrics through a binder-less and sintering aid-free thermoelectric nanowire ink system that can achieve dense thermoelectric structures (up to 82.5% theoretical density). The increase in density and corresponding enhancement of thermoelectric material efficiency are attained in a more tunable and controlled manner without compromising the material composition. A high filler-derived density index (FDI) of 2.51 is also achieved, implying the potential to obtain high-density parts with minimal filler content, thus unlocking a cascade of profound impacts. Crucially, this advancement enables the possibilities of anisotropic engineering in thermoelectric materials, thereby shattering the limitations that have hindered the widespread adoption of 3D printed inorganic thermoelectrics.

Suppressing Ag2Te nanoprecipitates for enhancing thermoelectric efficiency of AgSbTe2.

Thermoelectrics are a class of materials that provide interconversion between heat and electricity, with desirable traits such as low thermal conductivity and low electrical resistivity. AgSbTe2 has emerged as one of the leading materials in recent years due to its ultra-low thermal conductivity. However, one major hindrance in undoped AgSbTe2 is its high electrical resistivity and low Seebeck coefficient due to the presence of Ag2Te nanoprecipitates. In this work, we leverage on the combination of an off-stoichiometric composition and a non-equilibrium process to simultaneously enhance the properties of AgSbTe2 and its thermoelectric device performance. Microscopically, the Ag2Te-deficient starting composition combined with a non-equilibrium thermal process suppresses the Ag2Te nanoprecipitates in the material. In addition, it is evident from the density functional theory (DFT) electronic structure that Ag2Te deficiency results in a smaller lattice and higher density-of-states near the Fermi level, which simultaneously lower the electrical resistivity and increase the Seebeck coefficient. As a result, zT as high as 1.7 was achieved at 573 K. Additionally, when combined with a high room temperature zT of 0.75, a power conversion efficiency of 7.3% was achieved at a ΔT of 290 K. Crucially, the strategy in this work can inspire application in other ABX2 material systems to achieve improved thermoelectric performances.