Earth-Abundant Fe–Al–Si Thermoelectric (FAST) Materials: from Fundamental Materials Research to Module Development

Abstract

To develop an autonomous power generation technology to support an internet-of-things (IoT) society, we proposed low-cost and nontoxic Fe−Al−Si-based thermoelectric (FAST) materials consisting of an Fe 3 Al 2 Si 3 phase. Because of the cost-effectiveness and easy disposal of FAST materials, they are attractive for autonomous power supplies to drive IoT sensors and devices. While bismuth−tellurium-based thermoelectric power generation modules have been commercialized, the discovery of FAST materials opens an additional route to generate power from waste heat at room temperature under a small temperature difference, which will expand the diversity of applications of thermoelectric power generation modules. This paper reports the thermoelectric properties of FAST materials synthesized by conventional laboratory-scale synthesis and mass production processes, enhancement of power factor less than 600 K through homogenization and removal of metallic precipitations, development of thermoelectric power generation modules, and the results of power generation tests. The operation of temperature/humidity sensors and wireless transmission by Bluetooth low energy communication using FAST materials-based modules under a small temperature difference at room temperature was demonstrated.

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

“…However, the constituent elements of Bi and Te elements are rare, which motivates research and development of low-cost TE materials with potential for commercialization. Fe 2 VAl-based Heusler alloys and Fe–Al–Si TE (FAST) materials are typical examples of environmentally friendly TE materials that operate near room temperature that have been modularized. TE materials can be evaluated by the figure of merit, z , which is expressed as Here, S is the Seebeck coefficient, σ is the electrical conductivity, and κ total is the total thermal conductivity .…”

“…Although Fe 2 VAl-based materials have high PFs over a few mW m –1 K –2 , it is necessary to reduce their inherently high values of κ total in the range of 15–28 W m –1 K –1 . FAST materials have relatively high PFs (∼0.6–0.7 mW m –1 K –2 ), and low values of κ total in the range of 5–6 W m –1 K –1 , but further improvements in their power densities are required for practical applications. Band engineering is applied to many systems to improve PF.…”

First-Principles Study on Lattice Dynamics and Thermal Conductivity of Thermoelectric Intermetallics Fe3Al2Si3

“…κ can be considered as the sum of two portions: the electronic (κ el ) and lattice (κ ph ) thermal conductivity. Recently, an Fe-Al-Si ternary intermetallic compound Fe 3 Al 2 Si 3 has been considered as a promising candidate of a novel practical thermoelectric material for lowtemperature applications [2][3][4][5][6][7]. Although the ZT value of Fe 3 Al 2 Si 3 is much lower than any other practical thermoelectric materials, it has some significant advantages: (1) lowcost and non-toxic, (2) high chemical and thermal stabilities, (3) an excellent oxidation resistance, and (4) a good balance of mechanical properties [6,7].…”

“…Recently, an Fe-Al-Si ternary intermetallic compound Fe 3 Al 2 Si 3 has been considered as a promising candidate of a novel practical thermoelectric material for lowtemperature applications [2][3][4][5][6][7]. Although the ZT value of Fe 3 Al 2 Si 3 is much lower than any other practical thermoelectric materials, it has some significant advantages: (1) lowcost and non-toxic, (2) high chemical and thermal stabilities, (3) an excellent oxidation resistance, and (4) a good balance of mechanical properties [6,7]. Besides, recent efforts utilizing machine-learning to optimize power factor, S 2 σ, gave a significant enhancement of n-type value (~40%) [4].…”

“…Besides, recent efforts utilizing machine-learning to optimize power factor, S 2 σ, gave a significant enhancement of n-type value (~40%) [4]. A further improvement of power factor was recently achieved by alternating sample preparation processes [7]. A TEG module fabrication based on Fe 3 Al 2 Si 3 materials and its demonstration to drive IoT devices has already been launched in a collaborative research group between industry, government, and academia [7].…”