Porous Ag₂Se Fabricated by a Modified Cold Sintering Process with the Average zT Around Unity Near Room Temperature

Abstract

Silver selenide (Ag2Se) is a promising material for thermoelectric applications near room temperature. This work proposes a new fabrication route for bulk Ag2Se via a modified cold sintering process (mCSP) to enhance its figure‐of‐merit (zT). Unlike conventional CSP, mCSP employs thiol‐amine (TA) as a liquid medium that completely undissolves Ag2Se, leading to a free flow of the TA solution within interparticle channels. By sintering at temperatures above the boiling point of TA, the liquid evaporates, leaving behind a bulk Ag2Se material with a tube‐like porous structure (open pores). These induced defects strongly influence thermoelectric properties of Ag2Se, with a substantial increase in the Seebeck coefficient and decrease in electrical conductivity. The overall power factor of the mCSP sample with TA surpasses that of the control sample without TA, consistent with effective band modeling of Ag2Se. Moreover, the created micropores during mCSP effectively suppresses the thermal conductivity, leading to a maximum zT above 1.0 at 400 K by optimizing mCSP parameters. Importantly, the average zT within the 300–400 K range is around unity, representing one of the highest reported values. Further optimization of mCSP parameters can enhance average zT beyond unity, making Ag2Se more competitive with state‐of‐the‐art materials near room temperature.

A Route to High Thermoelectric Performance: Solution‐Based Control of Microstructure and Composition in Ag2Se

“…A) total thermal conductivity, B) lattice thermal conductivity, and C) lattice thermal conductivity plotted against the microstrain obtained from XRD peak width analysis. D) Power factor, E) thermoelectric figure of merit zT , and F. average zT compared with state‐of‐the‐art literature values between 300 and 387 K. [ 45,51,69–71 ]…”

Cold Sintering Mediated Engineering of Polycrystalline SnSe with High Thermoelectric Efficiency

“…As the first example, in the previous study, we have shown that the CSP-prepared PbTe 0.94 Se 0.06 has superior thermoelectric performance in comparison to spark plasma sintering prepared material owing to the low-temperature depressed Pb precipitation. Recently, thermoelectric materials such as Ca 3 Co 4 O 9 , CoSb 3 , and Ag 2 Se prepared by CSP have been reported, which show competitive performance compared with conventional sintering methods. Here, we demonstrate that in addition to the highly anisotropic structure, the high pressure of CSP can induce dislocations and stacking faults in SnSe with much higher strain compared to conventional sintering.…”