Thermoelectric Characteristics of β-Ag2Se1+x Prepared via a Combined Rapid Mechano-Thermal Approach

This study investigates the thermoelectric properties of Se-rich β-Ag2Se synthesized via a mechanochemical method followed by spark plasma sintering (SPS) in less than 30 min of the total reaction time. Importantly, only a short 10 min milling process followed by appropriate SPS was enough to produce single-phase Ag2Se1+x samples with varying selenium content (where x = 0, 0.01, 0.02, 0.04). The introduction of excess selenium significantly influenced the thermoelectric performance, optimizing the carrier concentration during synthesis and resulting in substantial thermoelectric improvements. The sample with nominal composition Ag2Se1.01 exhibited a high dimensionless figure-of-merit (ZT) >0.9 at 385 K, which is nearly six times higher than the reference sample (β-Ag2Se). Our findings bring valuable insight into the technology of optimization of thermoelectric characteristics of Se-rich β-Ag2Se, highlighting its potential for applications in thermoelectric devices. The study demonstrates the energetically efficient and environmental advantage of our mechanochemical route to produce Se-rich β-Ag2Se, providing a solvent-free and commercially viable alternative synthesis for energy (thermoelectric and solar energy).