Hierarchical Structures Advance Thermoelectric Properties of Porous n-type β-Ag2Se

Owing to the intrinsically good near-room-temperature thermoelectric performance, beta-Ag2Se has been considered as a promising alternative to n-type Bi(2)Te(3 )thermoelectric materials. Herein, we develop an energy- and time-efficient wet mechanical alloying and spark plasma sintering method to prepare porous beta-Ag2Se with hierarchical structures including high-density pores, a metastable phase, nanosized grains, semi-coherent grain boundaries, high-density dislocations, and localized strains, leading to an ultralow lattice thermal conductivity of similar to 0.35 W m(-1) K-1 at 300 K. A relatively high carrier mobility is obtained by adjusting the sintering temperature to obtain pores with an average size of similar to 260 nm, therefore resulting in a figure of merit, zT, of similar to 0.7 at 300 K and similar to 0.9 at 390 K. The single parabolic band model predicts that zT of such porous beta-Ag2Se can reach similar to 1.1 at 300 K if the carrier concentration can be tuned similar to 1 x 10(18) cm(-3), suggesting that beta-Ag2Se can be a competitive candidate for room-temperature thermoelectric applications.