Phase-modulated mechanical and thermoelectric properties of Ag2S1-x Tex ductile semiconductors

By virtue of the excellent plasticity and tunable transport properties, Ag2S-based materials demonstrate an intriguing prospect for flexible or hetero-shaped thermoelectric applications. Among them, Ag(2)S1-xTex exhibits rich and interesting variations in crystal structure, mechanical and thermoelectric transport properties. However, Te alloying obviously introduces extremely large order-disorder distributions of cations and anions, leading to quite complicated crystal structures and thermoelectric properties. Detailed composition-structure-performance correlation of Ag2S1-xTex still remains to be established. In this work, we designed and prepared a series of Ag2S1-xTex (x = 0-0.3) materials with low Te content. We discovered that the monoclinic-to-cubic phase transition occurs around x = 0.16 at room temperature. Te alloying plays a similar role as heating in facilitating this monoclinic-to-cubic phase transition, which is analyzed based on the thermodynamic principles. Compared with the monoclinic counterparts, the cubic-structured phases are more ductile and softer in mechanical properties. In addition, the cubic phases show a degenerately semiconducting behavior with higher thermoelectric performance. A maximum zT = 0.8 at 600 K and bending strain larger than 20% at room temperature were obtained in Ag2S0.7Te0.3. This work provides a useful guidance for designing Ag2S-based alloys with enhanced plasticity and high thermoelectric performance. (c) 2021 The Chinese Ceramic Society. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Due to their excellent plasticity and tunable transport properties, Ag2S-based materials have great potential for flexible or hetero-shaped thermoelectric applications. This study designed and prepared a series of Ag2S1-xTex materials with low Te content and found a monoclinic-to-cubic phase transition. The cubic-structured phases exhibited superior mechanical properties and thermoelectric performance compared to the monoclinic counterparts.