Mechanical and thermoelectric properties in Te-rich Ag2(Te,S) meta-phases
Yumeng Wang, Pengfei Qiu, Shiqi Yang, Zhiqiang Gao, Lidong Chen, Xun Shi
Abstract
Ductile Ag2(Te,S) pseudobinary compounds have attracted great attention in thermoelectric community since they can be fabricated into high-performance flexible and hetero-shaped thermoelectric devices for wearables. However, in spite of the numerous studies, the ‘brittle–ductile’ transition boundary in Ag2(Te,S) is still unclear. In this work, a series of Te-rich Ag2(Te,S) pseudobinary compounds have been prepared. The structure characterizations confirm they belong to the new-concept of meta-phase. The systematically investigation on the mechanical properties demonstrate that the ‘brittle–ductile’ transition boundary appears around x = 0.1. Unexpected good ductility is observed in the Te-rich Ag2Te1–xSx crystalizing in the Ag2Te room-temperature monoclinic structure and high-temperature cubic structure, which are thought to be brittle before. Likewise, Ag content is found to be a very critical parameter determining the ductility of Te-rich Ag2Te1–xSx. Very slight Ag-deficiency can greatly deteriorate the ductility. The thermoelectric properties of these ductile Te-rich Ag2Te1–xSx pseudobinary compounds are investigated. A maximum thermoelectric figure-of-merit of 0.6 is obtained for Ag2Te0·9S0.1 at 600 K. This work sheds light on the future investigation of Ag2(Te,S) pseudobinary compounds.