Study On Optimizing Thermoelectric Properties Of MnTe Materials By Nanocomposite And Carrier Concentration

Thermoelectric conversion technology is a green energy technology that uses semiconductor materials to convert thermal energy and electrical energy directly.Manganese telluride(MnTe)material has the advantages of non-toxic elements,abundant sources,and low cost.It is an eco-friendly medium temperature thermoelectric material with broad development prospects.In this paper,the thermoelectric properties of polycrystalline MnTe were optimized by nanocomposite and carrier concentration.SnTe nanocrystals were successfully nanocomposited to adjust energy band of MnTe material and promote energy band convergence.They were beneficial for the multivalence band transmission of carriers and the improvement of Seebeck coefficient.Simultaneously,SnTe nanocrystals enhanced phonon scattering and suppressed lattice thermal conductivity.The thermoelectric performance was signficantly optimized.Ge doping effectively increased the carrier concentration,leading to the enhanced electrical conductivity.The introduced point defects reduced the thermal conductivity.Ge doping realized the synergistic optimization of the electrical and thermal transport.The following research results are obtained:1.Mn_1.06Te-SnTe nanocomposite samples were successfully fabricated by the method of combining smelting and hydrothermal.The introduction of SnTe with intrinsic Sn vacancies resulted in a significant increase in the carrier concentration of MnTe materials.The energy band of SnTe was adjusted to promote the convergence of the MnTe energy band and reduce the energy difference of the MnTe valence band,which effectively promoted the multivalence band transmission of carriers and increased the Seebeck coefficient of the material.The enhancement of Seebeck coefficient and electrical conductivity significantly boosted the power factor.Simultaneously,SnTe nanocrystals significantly enhanced phonon scattering and achieved extremely low lattice thermal conductivity in the material.Therefore,the electrical and thermal transport performance of MnTe was improved through synergistic optimization.A peak ZT of 1.4 was achieved at 873 K in Mn_1.06Te-2%SnTe sample,which was dramatically enhanced by 133%compared with that of SnTe free sample.2.Ge doped Mn_1.06Te samples were synthesized by the smelting method.Due to the electronegativity difference between Ge and Mn,Ge doping increased the carrier concentration and effectively improved the electrical conductivity of MnTe.Meanwhile,Ge doping introduced a large number of point defects,which enhanced phonon scattering and greatly reduced the lattice thermal conductivity.The electrical and thermal transport performance of MnTe was synergistically optimized.As a result,the figure of merit of Mn_1.02Ge_0.04Te sample at 873 K reached 0.86.