Ge掺杂MnTe材料的热电输运性能

MnTe作为一种新型的无铅p型热电材料, 在中温区热电领域具有广阔的应用前景, 但其本身的热电性能不足以与高性能n型热电材料相匹配。本研究通过真空熔炼-淬火和放电等离子烧结的方法制备不同Ge掺杂量的致密且均匀的Mn_1.06-xGe_xTe(x=0, 0.01, 0.02, 0.03, 0.04)多晶块体样品。过量的Mn可以有效抑制MnTe₂相, 提高基体相的热电性能。通过掺杂4%Ge粉末, 材料的载流子浓度提高到7.328×10¹⁸ cm^-3, 电导率在873 K增大到7×10³ S?cm^-1, 功率因子提升至620 μW?m^-1?K^-2。同时, 通过点缺陷增强声子散射使材料的热导率降低到0.62 W?m^-1?K^-1, 实现了对材料电声输运性能的有效调控。Mn_1.02Ge_0.04Te在873 K获得了0.86的热电优值ZT, 较纯MnTe材料提高了43%。

Thermal and Electrcial Transport Properities of Ge Doped MnTe Thermoelectrics

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.