Research On Band Structure And Thermoelectric Properties Of Double-Doped SnTe-Based Thermoelectric Materials

The traditional middle-temperature thermoelectric material PbTe have extremely high thermoelectric properties and relatively mature development research,but the high content of toxic element severely limits its further application.SnTe,which has the same crystal structure and similar valence band structure as PbTe,has gradually become an environmentally friendly substitute for PbTe.In this paper,SnTe-based thermoelectric materials are used as the research object,a new type of smelting process is adopted to adjust the thermoelectric transport performance of SnTe through dual element co-doping（Mn-Sb and Ge-As）,and band convergence is introduced to increase the Seebeck coefficient of the material and improve it power factor,and finally optimize the thermoelectric figure of merit of SnTe through the regulation of coordinated electrothermal transport performance.The main research results are as follows:（1）In this paper,environmentally friendly SnTe samples with high thermoelectric performance were successfully prepared by one-step melting method combined with SPS sintering equipment.The study found that Sn self-compensation combined with Mn and Sb double-doped Sn_1.03-2xMn_xSb_xTe（x=0,0.02,0.04,0.06,0.08）sample results:the self-compensation effect fills the intrinsic Sn vacancies,reducing the carrier concentration,while Sb³⁺replaces Sn²⁺to provide a large amount of extra electrons,which compensates the intrinsic tin hole concentration and adjusts the carrier concentration to the optimal value again;Mn element doping leads to the convergence of the energy bands between the light and heavy valence bands to improve the energy band structure and make SnTe The Seebeck coefficient and power factor of the sample are significantly increased,while the band gap is widened,which effectively suppresses the bipolar effect.At 873 K,the synergistically optimized electrical and thermal transport properties enable it to achieve the highest ZT value of 1.4 at873 K,and an excellent average ZT of about 0.56 in the temperature range of 300K-873K.Compared with the SnTe system materials prepared by the traditional smelting method,the SnTe samples prepared in this experiment achieved high thermoelectric performance while maintaining the low cost of raw materials and being harmless to the environment.（2）The high-performance Ge-As co-doped polycrystalline SnTe sample was prepared by the smelting method,which greatly reduced the lattice thermal conductivity while increasing the Seebeck coefficient.Seebeck’s improvement is mainly due to Ge-As co-doping which significantly reduces the（35）E（L-（50））between the light and heavy valence bands and increases the band gap,improves the effective mass of holes,and realizes the band convergence of the light and heavy valence bands of SnTe.The increase in weight mobility also proves the optimization of the electrical properties of the sample.Finally,the sample with 2%doping at 873 K has the highest pyroelectric figure of merit Reached 0.74.