Thermal conductivity of semiconducting and metallic FeSi2

The thermal conductivity of β- and α-FeSi2 has been investigated at low temperatures (2 K < T < 90 K) and between room temperature and the transition temperature (1200 K). For undoped β-FeSi2 results are obtained, which are typical for pure crystals. Doping with Co and Al reduces the lattice thermal conductivity. A band gap (T = 0 K) of 0.9 eV can be calculated from the ambipolar range. The lattice thermal conductivity of α-FeSi2 is determined by a high concentration of Fe-vacancies.