Thermoelectric properties of Al-(Mn,X)-Si C54-phase (X = Ru and Re)

The lattice thermal conductivity of the Al-Mn-Si C54-phase, which possesses a large magnitude of the Seebeck coefficient and metallic electrical conduction, was greatly reduced by partial substitution of the heavy elements Ru and Re for Mn; these were selected by first principles calculations so as not to produce impurity states near the chemical potential. The heavy element substituted Al-Mn-Si-based C54-phase showed a drastic increase in the dimensionless of figure of merit ZT due to the reduction of the lattice thermal conductivity together with the unchanged electrical properties. The maximum ZT value of the p-type sample and the n-type sample reached 0.12 at 520 K and 0.38 at 540 K, respectively. These values are about five times larger than that of the heavy element-free Al-Mn-Si C54-phase.