| Abstrakt: |
Silver selenide (Ag2Se) stands out as a promising thermoelectric (TE) material, particularly for applications near room temperatures. This research presents a novel approach for the fabrication of bulk Ag2Se samples at a relatively low temperature (170°C) using the cold sintering process (CSP) with AgNO3 solution as a transient liquid agent. The effect of AgNO3 addition during CSP on the microstructure and TE properties was investigated. The results from phase, composition and microstructure analyses showed that the introduction of AgNO3 solution induced the formation of Ag nano-precipitates within the Ag2Se matrix. Although the nano-precipitates do not affect the phase and crystal structure of orthorhombic β-Ag2Se, they suppressed crystal growth, leading to reduced crystallite sizes. The samples containing Ag nano-precipitates also exhibited high porosity and low bulk density. Consequently, these effects contributed to significantly enhanced electrical conductivity and a slight decrease in the Seebeck coefficient when small Ag concentrations were incorporated. This resulted in an improved average power factor from ∼1540 µW·m−1·K−2 for pure Ag2Se to ∼1670 µW·m−1·K−2 for Ag2Se with additional Ag precipitates. However, excessive Ag addition had a detrimental effect on the power factor. Furthermore, thermal conductivity was effectively suppressed in Ag2Se fabricated using AgNO3-assisted CSP, attributed to enhanced phonon scattering at crystal interfaces, pores, and Ag nano-precipitates. The highest figure-of-merit (zT) of 0.92 at 300 K was achieved for the Ag2Se with 0.5wt% Ag during CSP fabrication, equivalent to >20% improvement compared to the controlled Ag2Se without extra Ag solution. Thus, the process outlined in this study presents an effective strategy to tailor the microstructure of bulk Ag2Se and enhance its TE performance at room temperature. [ABSTRACT FROM AUTHOR] |
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