Preparation And Study Of New Selenide Thermoelectric Materials

Thermoelectric materials could provide a clean and efficient way to solve the global energy and environmental crisis,because they could direct conversion between thermal and electrical energy,which enable reprocessing of waste energy the thermoelectric power generation and solid-state refrigeration and other fields have a wide range of applications.In this paper,SnSe and Bi₂Se₃ compounds were used as the research object to optimize and try to improve the thermoelectric properties.In the material synthesis,structure and physical properties of a more systematic research work.We explore the hot and hot materials to improve the value of hot spots and made a series of progress through the doping,nanocrystallization or introduction of nanocomposite materials?the main results and innovation points include the following aspects:The effect of changing the temperature of hot pressing and Zn doping on the thermoelectric properties of polycrystalline SnSe was studied.The maximum ZT value of polycrystalline SnSe was 0.73 when the temperature of hot pressing was 400 ? and 450 ?.By doping the polycrystalline SnSe thermoelectric material with zinc?Zn?,we obtained the ZT value was as high as 0.96 at 873K,which is about 40%higher than that of pure SnSe?ZT = 0.68?,it is due to the increasing of the electrical conductivity and the Seebeck coefficient.The effects of carbon black and PbTe nanoparticles on the thermoelectric properties of polycrystalline SnSe were studied.The results show that the ZT value of SnSe is up to 1.21 at 903K by adding an appropriate amount of carbon black as nano-inclusions to increase the electrical conductivity at high temperature.The PbTe nanoparticle composite SnSe improves the power factor and reduces the thermal conductivity,in result the ZT value was 1.26 at 880K.The thermoelectric properties of polycrystalline Bi₂Se₃ were studied.The results show that we can improve their thermoelectric properties through the repeated measurements.For the samples which were in the vertical and the parallel when hot pressing,the maximum thermoelectric ZT value were increaseed from 0.4 and 0.25 respectively to 0.62 and 0.35 after the repeated measurements,respectively.The enhancement of the ZT was mainly due to a significant increasing in the carrier mobility.Futhermore,the resistivity and the Seebeck coefficient show the topological metal conduction behavior perpendicular to the hot-pressing direction in the third measurement.It can prove that the topological metal conductance of the polycrystalline Bi₂Se₃.In addition,were studied the thermoelectric properties of Bi₂Te_2.7Se_0.3.The results show that nanocrystallization of Bi₂Te_2.7Se_0.3 can effectively reduce the thermal conductivity by grinding,so that the ZT value reaches 1.0 at 373K.However,we also found that the nanocrystallization can reduces the thermal conductivity while the power factor was also brought down.Therefore,we synthesized the InSb nanoparticles in Bi₂Te_2.7Se_0.3,and we find the thermal conductivity of Bi₂Te_2.7Se_0.3 was reduced by recombination,but the power factor remained almost unchanged at the same time.The ZT value was reached 1.2 at 323K.