Fe–Al–Si Thermoelectric (FAST) Materials and Modules: Diffusion Couple and Machine-Learning-Assisted Materials Development

Abstract

To lower the introduction and maintenance costs of autonomous power supplies for driving Internet-of-things (IoT) devices, we have developed low-cost Fe−Al−Si-based thermoelectric (FAST) materials and power generation modules. Our development approach combines computational science, experiments, mapping measurements, and machine learning (ML). FAST materials have a good balance of mechanical properties and excellent chemical stability, superior to that of conventional Bi− Te-based materials. However, it remains challenging to enhance the power factor (PF) and lower the thermal conductivity of FAST materials to develop reliable power generation devices. This forum paper describes the current status of materials development based on experiments and ML with limited data, together with power generation module fabrication related to FAST materials with a view to commercialization. Combining bulk combinatorial methods with diffusion couple and mapping measurements could accelerate the search to enhance PF for FAST materials. We report that ML prediction is a powerful tool for finding unexpected off-stoichiometric compositions of the Fe−Al−Si system and dopant concentrations of a fourth element to enhance the PF, i.e., Co substitution for Fe atoms in FAST materials.

Effect of Silicon on the Synthesis of Iron Aluminides from Elemental Powders

“…Silicon undergoes a eutectic transformation with aluminum [28], with a maximum melting temperature drop at 12.6 wt% of silicon. Silicon can also vary the degree of porosity [26]and the surface tension [29]. This also leads to a change in the morphology of the structure.…”

Effect of Pressure on Crystal Structure and Phonon Density of States of FeSi

“…Iron monosilicide (FeSi) serves as a specific example of a strongly correlated electron system with d-electrons, garnering significant attention due to its unconventional temperature dependencies concerning magnetic, − optical, elastic, transport properties, as well as its noncentrosymmetric crystal structure. FeSi is a narrow band gap semiconductor (0.18 eV) and a promising material for thermoelectric and solar applications. − Notably, the thermoelectric material based on Fe 3 Al 2 Si 3 showcases substantial conductivity and Seebeck coefficient values, with the FeSi microstructure playing a pivotal role in yielding a high-power factor . Additionally, doping FeSi with aluminum is noted to result in a heavy-Fermion metal with unique characteristics .…”

“…8−10 Notably, the thermoelectric material based on Fe 3 Al 2 Si 3 showcases substantial conductivity and Seebeck coefficient values, with the FeSi microstructure playing a pivotal role in yielding a high-power factor. 11 Additionally, doping FeSi with aluminum is noted to result in a heavy-Fermion metal with unique characteristics. 12 The tuning of magnetic properties within a narrow band gap semiconductor and exploring its non-Fermi liquid state due to impurities hold fundamental interest within spintronics, 13 nonvolatile memory devices, 14 and quantum many-body physics.…”

Effect of carrier doping on the electronic states of earth-abundant Fe–Al–Si thermoelectric materials

“…When considering practical use of thermoelectric power-generation devices, the thermoelectric materials should consist of readily available elements, that is, low-cost materials such as β-FeSi 2 [4], MnSi γ [5], Fe 2 VAl Heusler compounds [6], Mg-Ag-Sb/Mg-Bi-Sb-Te [7], Cu-S [8], and Zn-Sb [9]. Recently reported Earthabundant Fe-Al-Si (τ 1 -Fe 3 Al 2 Si 3 ) ternary thermoelectric materials [10,11], which are called FAST materials [12,13], are promising candidates for fabricating robust power-generation modules using low-temperature waste heat at temperatures less than 500 K [13] because they have excellent oxidation resistance and mechanical properties [14]. Takagiwa et al have demonstrated operation of temperature/humidity sensors and wireless transmission by Bluetooth low-energy communication with power-generation modules using p-and n-type FAST materials [12].…”