Origin of ductility in amorphous Ag2S0.4Te0.6

Amorphous Ag2S0.4Te0.6 shows outstanding ductility and promising thermoelectric properties at room temperature [He et al., Sci. Adv. 6, eaaz8423 (2020)], while the origin of its exceptional ductility is still not very clear. Here, we systematically investigate the temperature-dependent structure and thermodynamic behavior of the Ag2SxTe1-x (x = 0-1.0) system by means of in situ x-ray powder diffraction and dynamic thermodynamic analysis, respectively. Our experimental results reveal that the degree of crystallization in Ag2SxTe1-x varies continuously with the ratio of S and Te. The Ag2S0.4Te0.6 sample is composed of two amorphous phases, i.e., the S-rich and Te-rich Ag-2(S,Te) glasses. The S-rich Ag-2(S,Te) amorphous phase with the atomic ratio about Ag:S:Te = 66:21:13 is identified as the ductile phase, which is the origin of ductility in the Ag2S0.4Te0.6 sample. The Ag2S-based glass in the supercooled liquid state at room temperature behaves like a Newtonian fluid at low strain rates, leading to the excellent ductility of Ag2S0.4Te0.6. Our work demonstrates the great potential to design and realize flexible inorganic functional materials through amorphization.

Automated summary

This study investigates the temperature-dependent structure and thermodynamic behavior of the Ag2SxTe1-x system and reveals that the ductility of Ag2S0.4Te0.6 sample originates from the S-rich amorphous phase.