Effects of Addition of Si and Sb on the Microstructure and Thermoelectric Properties of GeTe
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The effects of the addition of Si and Sb on the microstructure and thermoelectric properties of GeTe were investigated in this study. Pure GeTe showed a typical herringbone structure that consisted of regularly aligned domains with alternating bright and dark contrast areas. When Sb atoms were added to the GeTe, a clean herringbone structure was not formed. Instead, many sharp lines that are likely narrow domains were observed, and their formation can be ascribed to the cubic stabilizing nature of Sb in GeTe. The co-addition of Si and Sb to GeTe resulted in a breakdown of the herringbone structure and formation of SiGe and Si precipitates. Even though Si and Ge can form a complete solid solution, the solubility of Si in GeTe remained low. The addition of Sb to GeTe significantly reduced the electrical conductivity due to the aliovalent donor nature of Sb. Its thermal conductivity was also very low due to the mass fluctuation in the solid solution and narrow domain structure. Therefore, the best figure-of-merit (ZT) of 0.67 at 570 K was obtained. However, Ge1−x−ySbxSiyTe compounds with both Si and Sb addition showed a relatively low ZT value.
KeywordsGeTe Herringbone structure Thermoelectric Microstructure
This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (Grant Number 2015R1D1A1A02062093). This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2018R1A41A1022260). This work was supported by a Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant from the Ministry of Trade, Industry and Energy, Republic of Korea (No. 20162000000910).