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

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 Fe₃Al₂Si₃ 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.