Silver sulfide is an inorganic semiconductor with extraordinary mechanical properties, especially in terms of ductility. However, conventional synthesis of silver sulfide used in thermoelectrics commonly requires complex and timeconsuming processes at high temperatures. Besides, the loss of sulfur during the preparation processes leads to difficult control over components. In this work, a high-pressure method is developed for the preparation of silver sulfide at reduced preparation temperature (573 K) and short time (10 min). The closed space of the high-pressure method prevents the sulfur loss, and all obtained samples show porous structures. Also, the Ag vacancies suppress the formation of Ag interstitials, thereby optimizing the carrier concentration and enhancing the electrical transport properties. On the other hand, the porous structures and Ag vacancy defects suppress the lattice thermal conductivities. Ag 1.96 S exhibits the highest figure of merit (ZT = 0.62) at 560 K, representing the highest value so far achieved by binary silver sulfide materials. In sum, a rapid, convenient, and component controllable approach is successfully developed for the preparation of high-performance silver sulfide-based materials with wide future application prospects.

The rattling-mode vibrations are unambiguously observed by Raman spectroscopy experimentally, leading to κL reducing by nearly 60% for SyCo4−xNixSb12 specimens.

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