| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 105 === Lead telluride is a classical thermoelectric material suitable for thermal energy harvesting at middle-high temperature regime. Besides typical hot-pressing technique, spark plasma sintering is commonly employed in fabricating quality lead telluride compounds. Nevertheless, how electric current affects lattice defects and microstructure of lead telluride is still not fully understood. In this study, we intend to investigate the current-induced lead migration and its impact on thermoelectric transport properties of lead telluride prepared by current-assisted sintering method. The process temperature is effectively lowered to 300 ℃ with the relative density up to 97.9%. The results indicate that the lead atoms are motivated under an electric field by forming many Pb vacancies in lead telluride. The carrier concentration of electrically sintered PbTe at room temperature is 2.09 * 10^18 compared to the hot-pressed PbTe with a value of 5.27 * 10^17 cm^-3. The carrier mobility increases from 390 cm^2/V*s. to 674 cm^2/V*s with the help of electrical sintering. Moreover, the electrically sintered PbTe demonstrates a large thermoelectric power factor of 1.66 mW/m*K^2 due to the greatly enhanced electrical conductivity. In addition, we have calculated the temperature-dependent thermoelectric properties of lead telluride with a multivalence band structure according to the Boltzmann transport equation.
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