The Role of Silver Nanowires in Modulating Electron and Phonon Transport in Ag2Se-based Thermoelectric Materials

Abstract

This study investigates the role of silver nanowires (AgNWs) in modulating the thermoelectric properties of bulk Ag₂Se nanocomposites. Ag₂Se samples with varying AgNW contents (0, 0.25, 0.5, and 1 wt.%) are synthesized using liquid-phase sintering, and their structural, morphological, and thermoelectric properties are thoroughly analyzed. X-ray diffraction confirmed the orthorhombic β-Ag₂Se phase as the primary structure, with a cubic silver (Ag) phase emerging at higher AgNW concentrations. SEM and TEM analyses showed that AgNWs are uniformly dispersed at lower concentrations, reducing porosity and enhancing relative density, while excessive AgNW content led to agglomeration, affecting both charge and phonon transport. Electrical conductivity increased significantly with AgNW addition due to enhanced charge injection and reduced activation energy, while the Seebeck coefficient exhibited a moderate decline. Optimal AgNW incorporation (0.25 wt.%) not only enhanced the power factor but also reduced lattice thermal conductivity, leading to a peak figure-of-merit (zT) of 0.79 at 320 K and an average zT of 0.74 across the 300–380 K range. The observed changes in thermoelectric properties of the Ag₂Se+AgNW nanocomposites are further elucidated through the calculation of the quality factor. These findings highlight the critical role of controlled AgNW addition in optimizing thermoelectric performance by balancing electronic and thermal transport properties.