Interface Engineering of Thermoelectric Materials Through Powder Atomic Layer Deposition (pALD)

• Applicant: Dr.-Ing. Amin Bahrami, Ph.D.
• Subject Area: Synthesis and Properties of Functional Materials
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 516355940

Thermoelectric (TE) materials are popular alternatives for energy conversion applications because of their superior performance and endurance. Extensive efforts are being made to improve their efficiency in single-/multi-phase composites containing second phases. The incorporation of second phases into the thermoelectric matrix can significantly improve their performance. When nano/micro-scale grain boundaries are achieved, high interface densities reduce heat conductivity, and specific electronic structural modifications will boost the power factor (PF) of TE materials. However, conventional fabrication procedures such as grinding or hydrothermal synthesis make it difficult to consistently synthesize multi-phase composites with optimal structures. On the other hand, high energies associated with multiple grain boundaries, render the nanostructure thermodynamically unstable, making it prone to spontaneous dissolution during the sintering process and long-term operation at elevated temperatures. Atomic layer deposition (ALD) as a non-line-of-sight deposition process of powders provides a unique approach to engineering the surface of thermoelectric particles thanks to its inimitable ability to deposit highly uniform and conformal films in a controlled manner which can solve both aforementioned concerns. Therefore, the purpose of this project is to improve the phonon scattering and/or boost the PF of various types of thermoelectric materials (Mg3Sb2, Bi2Te3 and half-Heusler compounds) by precise deposition of selected materials (Oxide, semiconductors and metals) on surface of each single particle using ALD technique. Aside from TE material synthesis, new ALD formulations must be developed to fulfill the needs of coping with air/moisture sensitive TE materials. We expect that in this proposal, we will not only aim to improve the phonon scattering or the PF, but that our results in the development of a novel ALD formulation might be of interest in other areas on investigation including but not limited to catalysis, sensors, 3D metal printing and so on.

• DFG Programme: Research Grants
• International Connection: USA
• Co-Investigator: Dr. Ran He
• Cooperation Partner: Professor Zhifeng Ren