Optimal Preparation Of Composite Doped Skutterudite Thermoelectric Materials

This thesis elaborated the preparation of composite doped skutterudite thermoelectric materials under high temperature and pressure conditions,also conducted testing and research on its thermal and electrical properties.By adjusting the experimental pressure,temperature,time and doping element ratio,the performance of thermoelectric materials is optimized,the electrical transport performance of the material is improved,and the thermal conductivity is reduced.The results show that the high temperature and pressure conditions can greatly shorten the synthesis time,produce abundant dislocations,increase the crystal defect rate,nucleation rate,enrich the grain boundary,and improve the mechanical properties of the synthesized sample.The main results obtained in this paper are as follows:(1)Based on the S-filled skutterudite thermoelectric material,the replacement of Te in different proportions is carried out to prepare S_yCo₄Sb_12-xTe_x(x=0.3,0.4;y=0.05,0.1).The results show that high-pressure can change the carrier concentration and optimize the electrical transport performance.Measured at room temperature,as the synthesis pressure continues to increase,the absolute value of the Seebeck coefficient of the sample shows an increasing trend.Among them,the sample S_0.05Co₄Sb_11.7Te_0.3 obtains the maximum power factor of 18.91?Wcm^-1K^-2 at 2.0 Gpa.(2)The study found that with the increase of the temperature,the thermal conductivity of the S_0.05Co₄Sb_11.6Te_0.4 samples prepared under different synthesis pressures showed a continuous downward trend.The ZT value gradually increases as the temperature rises.Among them,the sample performance is good when the synthetic pressure is 3.0 Gpa,the lattice thermal conductivity is 1.23 Wm^-1K^-1 and the ZT value of the sample reaches 1.07 at the end of the test temperature.It shows that the conditions of high temperature and pressure can improve the electrical transport performance of the material,at the same time it can increase the dislocation,reduce the crystal grain size and lattice thermal conductivity,then finally achieve the purpose of optimizing the material's thermoelectric merit.(3)On the basis of composite doping of S and Te,In doping was added to prepare In_xS_yCo₄Sb_11.6Te_0.4(x=0.05,0.1;y=0.05,0.1)samples.The study found that comparing with single S-filled,the electrical transport performance of In-S double-filled skutterudite material is further improved.Within the synthetic pressure range,the absolute value of Seebeck coefficient of all samples increases with the growth of synthetic pressure.When the synthetic pressure is at 3.5 Gpa,the sample In_0.05S_0.05Co₄Sb_11.6Te_0.4's Seebeck coefficient is 193.8?VK^-1,which is the maximum value can be obtained at room temperature,and the power factor of the sample reaches 17.84?Wcm^-1K^-2.