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Reducing Lattice Thermal Conductivity of MnTe by Se Alloying Toward High Thermoelectric Performance.

Lead-free manganese telluride has been considered to be a promising candidate for mid-temperature thermoelectric materi-als. In this work, we report a point defect scattering induced reduction of thermal conductivity in MnTe with Se alloying, fabricated by a facile method combining mechanical alloying (MA) and spark plasma sintering (SPS). A low lattice thermal conductivity of 0.56 W/m-K was obtained for MnTe0.92Se0.08, which is quite close to the amorphous limits. A detailed Debye model analysis reveals the underlying mechanism of phonon scattering and well predicts the thermal conductivity with dif-ferent contents of Se. Meanwhile, a slight increase of carrier concentration was also observed after Se alloying, accompanying a variation of energy gap which may be associated with the competition of anion in trapping charges. Further Na doping leads to enhanced electrical transport properties, achieving a maximum ZT value of 1.03 at 873 K. An average ZT of 0.52 and a calculated efficiency over 9% also suggest the promising application of MnTe at medium temperature.