Study On The Preparation And The Performance Optimization Of Medium-Room Temperature Thermoelectric Material Bi₂?Se,Te?₃

Thermoelectric material is a green cleaning material,urtilizing the transport properties of carriers and phonons to convert heat into electricity,which has the great competitiveness and prospects in the field of new energy.In this paper,the preparation and performance optimization of medium-room temperature thermoelectric material Bi₂?Se,Te?₃ are studied.Bi₂Se₃ and Bi₂Te₃ materials belong to the same three-dimensional topological insulator,and have excellent performance in the field of thermoelectric applications.Among the Bi₂Se₃-based materials,Sb alloyed Bi₂Se₃?BiSbSe₃? material has excellent thermoelectric properties in the medium temperature application region,and we found that In alloyed Bi₂Se₃?BiInSe₃? also has a very large research value in the field of thermoelectricity.Among the Bi₂Te₃-based materials,the Sb alloyed Bi₂Te₃(Bi_0.46Sb_1.54Te₃) material has excellent thermoelectric properties in low temperature applications.Bi₂Se₃ belongs to medium-temperature thermoelectric materials,and its thermoelectric performance reaches the maximum in the middle temperature region.Due to its good electrical transport properties and high Seebeck coefficient,it is considered to have potential medium-temperature thermoelectric materials.However,for the thermoelectric performance of Bi₂Se₃,its intrinsic thermal conductivity is high,which limits the intrinsic thermoelectric performance.We have prepared Bi₂Se₃-based thermoelectric material by a conventional solid phase sintering method combined with plasma rapid sintering?SPS?.The specific research work is as follows:1.In alloyed Bi₂Se₃ forms a BiInSe₃ thermoelectric material and belongs to an n-type semiconductor.The main work of this research is to make In replace the position of Bi atom in Bi₂Se₃ and then form BiInSe₃ thermoelectric material.Compared with Bi₂Se₃,BiInSe₃ has similar intrinsic thermoelectric properties to BiSbSe₃ material,and has a very high Seebeck coefficient and low thermal conductivity.However,the electrical conductivity is extremely low,and it is also necessary to increase the conductivity by a corresponding method of increasing the carrier concentration.2.The n-type BiSbSe₃ thermoelectric material possesses is a very high Seebeck coefficient and low thermal conductivity,whihch is considered as a promising medium-temperature thermoelectric material.However,it is necessary to increase the conductivity by a corresponding method of increasing the carrier concentration due to the low electrical conductivity of BiSbSe₃.In this work,the non-equivalent anion and cation co-doping is achieved by doping SnCl₄ in the BiSbSe₃ matrix to improve its thermoelectric performance.Sn atom replaces the position of the Bi/Sb atom,and Cl atom replaces the position of the Se atom,and synergistically provides additional electrons,thereby increasing the carrier concentration and achieving the purpose of improving the electrical conductivity.Combined with the low thermal conductivity of BiSbSe₃,the maximum ZT value reaches 0.61 at 773 K.Bi₂Te₃ belongs to p-type semiconductor is the most promising traditional commercial thermoelectric material,which achieves optimal thermoelectric performance near room temperature.Among the thermoelectric materials based on Bi₂Te₃,the BiSbTe alloy material has excellent thermoelectric properties.In this work,Bi_0.46Sb_1.54Te₃ material was prepared by mechanical alloying method combined with plasma rapid sintering technology,and the thermoelectric performance optimization of Bi_0.46Sb_1.54Te₃ material was studied.The specific research work is as follows:1.Bi_0.46Sb_1.54Te₃ thermoelectric material containing nano-precipitates was prepared by mechanical alloying method.The thermoelectric performance of Bi_0.46Sb_1.54Te₃ was improved by the energy filtering effect induced by nanoprecipitates,lifting the ZT value of Bi_0.46Sb_1.54Te₃ at 325 K.In order to further enhance the thermoelectric properties of Bi_0.46Sb_1.54Te₃,a small amount of nano-silicon carbide?SiC?was doped into the Bi_0.46Sb_1.54Te₃ matrix to form a nanocomposite.The addition of SiC increases the conductivity and Seebeck coefficient,while the lattice thermal conductivity decreases slightly under the optimal SiC doping amount.Therefore,the ZT value of the Bi_0.46Sb_1.54Te₃/SiC composite reaches 1.45 at 325 K.2.Using the design strategy of the thermoelectric hetero nano region,we introduce another thermoelectric material?SnTe? with a small lattice lattice matching degree in the Bi_0.46Sb_1.54Te₃matrix.The thermoelectric nano-hetero region decouples the electrical and thermal transport properties,which increases the antisite Bi/Sb_Te defects and then increases the carrier concentration.Simultaneously,the lattice interface with a small matching degree maintains almost no change in mobility,increasing the electrical conductivity.The presence of nano-hetero regions reduces the lattice thermal conductivity.Therefore,the addition of SnTe increases the ZT value to 1.45 at 325K.