Nanoscale Zinc Antimonides: Synthesis and Phase Stability

Unexpected high-temperature stability of β-Zn4Sb3 opens the door to enhanced thermoelectric performance

β-Zn4Sb3 has one of the highest ZT reported for binary compounds, but its practical applications have been hindered by a reported poor stability. Here we report the fabrication of nearly dense single-phase β-Zn4Sb3 and a study of its thermoelectric transport coefficients across a wide temperature range. Around 425 K we find an abrupt decrease of its thermal conductivity. Past this point, Zn atoms can migrate from crystalline sites to interstitial positions; β-Zn4Sb3 becomes metastable and gradually decomposes into Zn(hcp) and ZnSb. However, above 565 K it recovers its stability; in fact, the damage caused by decomposition can be repaired completely. This is key to its excellent thermoelectric performance at high temperature: the maximum ZT reaches 1.4. Molecular dynamics simulations are used to shed light on the microscopic behavior of the material.

Low-cost high-performance zinc antimonide thin films for thermoelectric applications

Zinc antimonide thin films with high thermoelectric performance are produced by a simple sputtering method. The phase-pure Zn(4)Sb(3) and ZnSb thin films fulfill the key requirements for commercial TE power generation: cheap elements, cheap fabrication method, high performance and thermal stability. In addition, two completely new meta-stable crystalline phases of zinc antimonide have been discovered.

Nanostructure-based thermoelectric conversion: an insight into the feasibility and sustainability for large-scale deployment

Significant scientific progress has been achieved using nanostructured materials for thermoelectric energy harvesting and solid-state cooling through the conversion of waste heat into electricity and vice versa. However, the connection between the small-scale proof-of concept results achieved in research labs and real industrial scale manufacture is still missing. Herein we develop an analysis to determine the appropriate thermoelectric nanomaterials for the large-scale manufacture and deployment in the near future. We cover key parameters such as ZT value, cost, abundance, and toxicity. Maximum ZT values are considered at three temperature ranges. Material cost and abundance are visually demonstrated to improve ease of interpretation. Toxicity is also evaluated to minimize the environmental impact during manufacture and recycling. Lastly, a parameter termed "efficiency ratio" is calculated to give a better qualitative understanding of the feasibility and sustainability of these nanomaterials.

Reacting the Unreactive: A Toolbox of Low-Temperature Solution-Mediated Reactions for the Facile Interconversion of Nanocrystalline Intermetallic Compounds

Metallurgical materials, including intermetallic compounds, are notoriously inert toward low-temperature reactivity. However, as nanocrystals, their reactivity is significantly enhanced. Here we show that intermetallic PtSn and AuCu nanocrystals can be converted, in solution at low temperatures, into derivative intermetallics. For example, PtSn can be converted into PtSn2 and Pt3Sn by reaction with SnCl2 and K2PtCl6, respectively. The reactions are also reversible, for example, the sequences PtSn --> PtSn2 --> PtSn and PtSn --> Pt3Sn --> PtSn are all readily achievable. The strategy also allows nanocrystalline AuCu to be successfully converted into AuCu3 via reaction with Cu(C2H3O2)2.H2O, suggesting that this approach may be general.