| Summary: | 碩士 === 國立新竹教育大學 === 應用科學系碩士班 === 105 === Thermoelectric materials can be used "doping" approach to change the microstructure, and improve the ZT value. In this study, the zone melted p-type Bi0.5Sb1.5Te3 thermoelectric materials with high orientation and texture were prepared with by doping different Te content, 0, 2.5, 3.0, 3.5 and 4.0 wt. %, respectively. The lattice constant maximum of the p-type thermoelectric materials is was located at 3.0 wt. % Te, and the c axis is 7 times as much as the a-axis, because the direction of crystal growth with anisotropy in the c-axis direction. In the thermoelectric properties, the optimum ZT value is 1.15 at 340 K. The results of microstructure and composition analysis, show the excess Te-doped was increased to 3.5 wt. % with the two-phase structure on the microstructure. The segregation phase was confirmed by TEM was pure Te, while the addition of appropriate amount of tellurium (Te) contributes to the improvement of the thermoelectric properties. However the "excess" leads to excessive segregation, which decreases the electrical conductivity and the thermal conductivity.
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