Abstract: MnTe is a promising candidate for the p-type lead-free thermoelectric material in middle temperature application. However, its thermoelectric performance isn’t qualified for some conventional n-type materials to form efficient thermoelectric devices. In this study, Mn_1.06-xGe_xTe (x=0, 0.01, 0.02, 0.03, 0.04) polycrystalline block samples with different Ge doping contents were efficiently synthesized by vacuum melting quenching and spark plasma sintering. The as-obtained Mn_1.06-xGe_xTe bulk was dense and consisted of homogeneous composition. Tiny extensive Mn can effectively restrict the formation of the second phase of MnTe₂ and improve the thermoelectric properties of the matrix phase. Electrical conductivity of the materials increasing to 7×10³ S∙cm^-1 results from the enhanced carrier concentration 7.328×10¹⁸ cm^-3 at 873 K, which contributed to a power factor of 620 μW∙m^-1∙K^-2 by 4% Ge doping. Meanwhile, Mn_1.06-xGe_xTe showed the reduced thermal conductivity of 0.62 W∙m^-1∙K^-1 by enhanced phonons scattering intensified with point defects, realizing the effective regulation of both electrical- and thermal-transport properties. Mn_1.02Ge_0.04Te achieved a thermoelectric performance of 0.86 at 873 K, which evolved by 43% compared with the pristine sample.

Key words: MnTe thermoelectric material, Ge doping, carrier concentration, lattice thermal conductivity