Thermoelectric properties of non-stoichiometric MnTe compounds

Non-stoichiometric Mn x Te1−x (x = 0.48–0.52) has been prepared by a melt-quench process followed by spark-plasma-sintering to investigate its thermoelectric properties. Polycrystalline Mn x Te1−x with x > 0.51 has a nearly single MnTe phase. The measured Seebeck coefficient and electrical conductivity show a similar trend, in which a transition occurs near 473 K with increasing temperature. The thermal conductivity of Mn x Te1−x compounds shows a tendency to decrease with increasing Mn content. Along with a low thermal conductivity and a high power factor, the samples with x > 0.51 have a high figure of merit, which reaches 0.41 at 773 K. The results indicate that production of a homogenous MnTe single phase is an effective way to improve the thermoelectric properties of p-type non-stoichiometric Mn x Te1−x compounds.