Thermoelectric Properties of Co- and Mn-Doped Al2Fe3Si3

Abstract

Al2Fe3Si3 is a promising semiconductor for application as an environmentally friendly thermoelectric material. Its intrinsic carrier concentration is 5 × 1019 cm−3 and shows p-type conduction. In this article, we report on the thermoelectric properties of carrier-doped Al2Fe3Si3. Co or Mn was substituted for Fe for electron or hole doping, respectively. Al2Fe3−xMxSi3 (M=Co or Mn; x = 0.1–1.0 for Co and 0.1–0.3 for Mn) samples were synthesized by arc melting followed by spark plasma sintering and heat treatment. The Co- and Mn-doped samples displayed Hall carrier concentrations of 1.4 × 1020 cm−3 to 5.1 × 1020 cm−3 for n-type and 1.3 × 1020 cm−3 to 1.3 × 1021 cm−3 for p-type conduction. The n-type Al2Fe3Si3 exhibited a higher absolute value of Seebeck coefficient and lower Hall carrier mobility than p-type Al2Fe3Si3 at the same carrier concentration. The power factor increased with increasing carrier concentration for n-type conduction, and reached 0.65 × 10−3 W/mK at 520 K. On the other hand, the power factor for p-type Al2Fe3Si3 was not enhanced with increasing carrier concentration. The maximum ZT value for Co-substituted Al2Fe3Si3 was 0.09 at 600 K, which is 50% higher than that of pure Al2Fe3Si3.