PbTe系列合金為中溫域最著名之熱電材料，為提升PbTe塊材的熱電轉換效率，本研究旨在檢討如何製備出奈米晶粒尺寸之PbTe塊材。研究項目包括： (1) 如何結合化學法及水熱法之優點而合成奈米大小的PbTe粒子，並提高其產粉效率， (2) 探討火花電漿燒結的燒結溫度與持溫時間對燒結體粒徑之影響及其氧化物之生成關係 (3) 探討奈米塊材之微觀結構對載子傳輸之影響。
本研究利用水熱爐的高壓還原特性及化學法的分段化學反應提出二階段水熱法，此法以600 ml的高壓釜，反應物Pb(NO3)2、Te各為0.06 mole時可於110 oC反應1小時而合成出單一相的PbTe奈米粉末，其粒子大小在10~40 nm，每次產量可達20 g。但粉體表面有氧化現象，氧含量約25 at%。合成的粉體經200 oC持溫3分鐘的SPS燒結，可製備出平均粒徑129 nm之緻密燒結體(相對密度 > 95 %)；更高的燒結溫度則會使原本附著在粉體表面的非晶質氧化物結晶成PbTeO3而析出於PbTe晶界。而載子在PbTe奈米塊材中的移動是由晶界散射所主導。

PbTe based alloys are one of the best intermediate temperature thermoelectric materials. This research focus on fabricating dense PbTe bulk with nano-sized grains to enhance the thermoelectric conversion efficiency; including three items . (1) Combing the advantages of hydrothermal method and low temperature wet chemical route to synthesize PbTe nanoparticles and to enhance the yield. (2) To investigate the relationship between the microstructures and the sintering parameters (sintering temperature and holding time) of SPS. (3) To investigate the relationship between the microstructure and the electrical properties.
Two steps hydrothermal method was proposed to synthesize PbTe nanoparticles. This method reproducibly synthesizes 10-40 nm nanocrystals at 110 oC for 2 h and has a high yield over 20 g per batch. The result also indicates surface oxidation on the nanocrystals, and the average oxygen content is about 25 at%. Dense PbTe nanocomposites were obtained by spark plasma sintering of as-synthesized nanoparticles at 200 oC for 3 min. The average grain size of this nanocomposite is 129 nm and the relative density is over 95%. The electrical properties are related to the microstructure which suggests that the transport properties are dominated by grain boundary potential barrier scattering.

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