Preparation And Thermoelectric Properties Of Hot-pressed Textured P-type Bismuth Telluride-based Materials

Bismuth telluride?Bi₂Te₃?materials have wide and important applications in semiconductor refrigeration and thermoelectric power generation near room temperature.However,commercial zone-melted bismuth telluride material has many problems,such as poor mechanical properties and easy cleavage.Not only is the material utilization rate low,but it is also easy to cause device failure.Therefore,the mechanical and thermoelectric properties of bismuth telluride materials need to be improved to meet the need of a wider range of application.In this paper,BiSbTe is composited with AgSbTe₂ material with low thermal conductivity near room temperature to optimize the electrical performance while reducing the thermal conductivity,thereby achieving the improvement of the overall performance of the material.Moreover,the polycrystalline bulk BiSbTe materials are prepared by hot deformation process,the thermoelectric properties of the hot deformed samples at different temperatures was explored,and the optimal hot deformation temperature was optimized.On this basis,Cu doping was used to reduce the lattice thermal conductivity of the material,and the thermoelectric performance of the p-type BiSbTe material was further optimized.The specific research contents are as follows:1.BiSbTe-x wt%AgSbTe₂?x=0,0.05,0.1,0.2?composite materials were prepared by hot pressed sintering process.The composite of AgSbTe₂ has less effect on carrier mobility while optimizing the carrier concentration.When the composite amount is 0.1 wt%,the power factor reaches the maximum value of 46?W cm^-1 K^-1 at 300 K,which is close to the zone melting sample(48?W cm^-1 K^-1).The composite of AgSbTe₂ also enhanced phonon scattering and the lattice thermal conductivity was significantly reduced.Finally,the sample with 0.1 wt%AgSbTe₂ composite obtained a maximum ZT value of 1.15 at 325 K,which was improved 44%compared to the matrix.2.Based on the hot pressing temperature of 673 K,the effects of different hot deformed temperatures of 773 K,803 K,and 823 K on the thermoelectric properties of bismuth telluride materials were studied.The results show that the hot deformation?HD?process can obtain a higher electrical performance than hot pressing?HP?;when the hot deformed temperature is 803 K,the thermal conductivity of Bi SbTe lattice is also effectively reduced.Finally,the optimal thermoelectric performance was obtained in BiSbTe material with hot deformed temperature of 803 K.The sample reached the highest ZT value of 1.0 at 350 K,which was higher than that of HP-BiSbTe sample?0.8@350 K?.3.Based on the optimized thermal deformation process,a series of Cu-doped CuxBi_0.48Sb_1.52Te₃?x=0,0.005,0.01,0.015?materials were prepared by the hot deformation process.Compared with hot pressing,the degree of texturing is reduced during the hot deformation process,but the grain boundaries are reduced,the grains grow from 2.4?m to 3.0?m,thus the carrier mobility is greatly improved.The HD-Bi SbTe sample has a carrier mobility of 250 cm² V^–1 s^–1 at room temperature,which is much higher than the 170cm² V^–1 s^–1 of the HP-Bi SbTe sample.During the process of Cu doping and hot deformation,a large number of point defects and nano-scale dislocations are generated,which enhances phonon scattering and reduces the room temperature lattice thermal conductivity from 1.0W m^–1 K^–1 to 0.6 W m^–1 K^-1.Finally,when x=0.01,the HD-Cu_0.01BiSbTe sample achieved a maximum ZT value of 1.1 at 400K.