| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 95 === Bi2Te3 is the most outstanding thermoelectric material near room temperature region. It has a laminar crystal structure with van der waals bonding in it. In this study, FeTe2 and In2Te3 were alloyed with Bi2Te3 respectively to investigate their microstructures and thermoelectric properties. For the FeTe2-Bi2Te3 system, the strip-like FeTe2 phase was found to segregate upon solidification and apart from each other by 1 �慆 approximately. According to theoretical calculation, it is found that the segregations have little influence on the scattering mechanism of charge carriers. Instead, Fe atoms which dissolved in Bi2Te3 lattice may change the carrier concentrations and thermoelectric properties of the alloys. The Seebeck coefficient and electrical resistivity of Bi2Te3 will decrease with the addition of FeTe2, leading to a lower power factor. For In2Te3-Bi2Te3 system, most of the indium atoms are still dissolved in Bi2Te3 crystal lattice which is not consistent with the equilibrium phase diagram published. The dissolution of indium results in the decrease in Seebeck coefficient and electrical conductivity of the alloys. The hole conduction is also found to change into electron conduction at a very high level of indium addition.
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