Effect of Composition Regulation on Thermoelectric Properties of Fe3Al2Si3-Based Compounds.

Fe₃Al₂Si₃-based thermoelectric materials have low production costs and are environmentally friendly. However, they are usually synthesized via arc-melting, resulting in poor compositional accuracy. Here, Fe_36.5Al_{23.5 + x}Si_40−x (x = 1.7, 1.8, 1.9, 2.0, and 2.1) compounds with low thermal conductivity (κ) were prepared via levitation melting. The x = 2.1 composition may be the threshold for a p-to-n-type transformation. A minimum κ of ~3.17 W/mK was obtained in Fe_36.5Al_25.4Si_38.1 at 323 K, a decrease of 42.3% relative to the parent Fe₃Al₂Si₃ compound. Moreover, the largest maximum power factor of ~461 μW m⁻¹ K⁻² was obtained in Fe_36.5Al_25.4Si_38.1 at 373 K. Using composition self-tuning, a peak figure of merit of ~0.055 was obtained in Fe_36.5Al_25.4Si_38.1 at 423 K. This approach for realizing low κ and a high compositional accuracy should impact the development of advanced room-temperature thermoelectric materials with narrow bandgaps. [ABSTRACT FROM AUTHOR]