金属硅化物热电材料中声子在晶体缺陷处的散射研究

The possibility and practicability to improve the thermoelectric properties of iron disilicide based alloys by the enhancement of phonon scattering by grain boundaries or dispersed nano-sized particles has been studied to develop the state-of-the-art thermoelectric materials for the application in thermoelectric cooling and power generators. It was shown that a decrease of about 25% on the thermal conductivity of b-FeSi2 based alloys could be expected if the grain sizes were decreased down to about 2mm by rapid solidification and hot pressing and nano-sized nitrides were dispersed in the materials by in-situ synthesis. A high figure of merit over 2′10-4/K has been measured in the manganese doped iron disilicides, which is comparable to the highest value ever reported for the similar thermoelectric materials. Pseudo- oriented solidification microstructures have been found in the rapidly solidified iron disilicide ribbons, and lead to textured structures in the bulk b-FeSi2 based alloys, which means there exists some orientation relationship between the a- and b-FeSi2 phase. It was found for the first time in b-FeSi2 based thermoelectric materials that a p-type semiconductor could change to an apparent n-type one, when the temperature was decreased below a critical temperature. Some thermoelectric characterization devices have been installed and other thermoelectric materials such as Bi2Te3 based alloys and Zn4Sb3 have been also studied.

热电材料在低品位能源利用和环境保护方面具有重要应用前景。降低材料中声子热导率是提高热电材料的转换效率的潜在有效途径。本项目采用多种材料制备技术，通过系统研究50纳米至50微米不同晶粒尺寸范围硅基热电材料中晶界等晶体缺陷对声子散射的作用，阐明晶体缺陷与热电材料热导率之间的关系，进而探索通过组织优化提高热电材料性能的可行性途径。.