Characterizations of Thermoelectric Material Bi0.3Sb1.5Te3 with Excess Tellurium Atoms and Aerogel-based Treatment by X-ray Absorption Spectroscopy

• Main Authors: Cheng-Wei Ku, 辜振維
• Other Authors: Shih-Yun Chen
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/t2kfa8

碩士 === 國立臺灣科技大學 === 材料科學與工程系 === 105 === With the world’s growing energy needs and climate drastically changing, creating innovative ways to obtain energy by low influence burden to the earth is the development directions of the modern energy issue. Having been regarded as potential energy conversion materials, thermoelectric materials which move conveniently by small solid-state size convert energy directly, rapidly and reversibly between thermal and electrical energy. Decades of researching, the development of thermoelectric materials is limited with the low conversion efficiency, so looking for more suitable materials or optimizing the existing materials to enhance their thermoelectric properties is the main research direction in this field. Bi-Te based alloy is the thermoelectric material that widely used within low temperature range, so we took Bi0.5Sb1.5Te3 (BST) as the substrate, applying the liquid flow method and aerogel method respectively and at the same time. Then we successfully changed the samples’ thermoelectric properties and increased the conversion efficiency significantly. According to the reference, the excess tellurium atoms on the grain boundary can be caused by liquid flow method; and nanoscale porous structure can be generated in materials by aerogel method. As mentioned above, those mechanisms are expected to increase the phonon scattering and to reduce the phonon thermal conductivity (KL), so that the ZT value can be enhanced. In this study, we probed into the correlation between thermoelectric properties and electron-orbital interaction upon the fixed local structure symmetry. Correlations between local atomic/electronic structure and thermoelectric properties are investigated by Extended X-ray absorption fine structure spectrum (EXAFS). Our results show that the bond length between the atoms is changed and the lattice sequence is also affected by the different processing method for BST.