| Summary: | 碩士 === 國立彰化師範大學 === 物理學系 === 98 === Abstract
Thermoelectric materials are characterized by the figure of merit Z = S2/ρκ, where ρ, S, and κ are the resistivity, thermopower, and thermal conductivity, respectively. Turning the current best thermoelectric materials into nanosize or nanostructure might help improve thermoelectric figure of merit by increasing the thermoelectric power as a result of an enhanced density of states and by reducing thermal conductivity as a result of an increased phonon scattering. Bismuth antimony telluride Bi2-xSbxTe3 mixed crystals have the best dimensionless thermoelectric figure of merit remained around 1 for more than 50 years. The p-type Bi0.45Sb1.55Te3 is synthesized using hydrothermal methods and followed by cold pressing and evacuated encapsulation. The resulting parallelepiped was sintered at various temperatures. For one of our samples, we show that a peak ZT of 1.53 at room temperature and 1.7 at 280K can be achieved in a p-type Bi0.45Sb1.55Te3 bulk alloy. Electrical transport measurements, coupled with microstructure studies and modeling, show that the ZT improvement is the result of low thermal conductivity caused by the increased phonon scattering by grain boundaries and defects. More importantly, ZT is about 1.53 at room temperature and 1.7 at 280K, which makes the material useful for cooling and power generation.
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