Thermoelectric and thermal stability improvements in Nano-Cu2Se included Ag2Se

Abstract

Recently, silver chalcogenides have attracted great attention due to their potential application for room temperature power generation and local cooling. In this work, we report the thermoelectric properties and thermal stability of bulk Ag2Se with nano-Cu2Se inclusions ((Ag2Se)(1-x)(Cu2Se)(x) where x = 0, 0.02 and 0.05). Ag2Se samples were prepared via melting, annealing and the nanocomposite was prepared by ball milling this material with required amount of nano-Cu2Se; finally, the samples were consolidated by spark plasma sintering. High temperature and low temperature transport properties were assessed by the measurements of the Seebeck coefficient, electrical conductivity, thermal conductivity, and Hall coefficient. The phase composition and microstructure were explored by powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM) with energy dispersive Xray (EDX) analysis, while the thermal stability of samples was investigated via heating microscopy and heat capacity measurement. Room temperature PXRD and SEM indicated that two separate phases of Ag2Se and Cu2Se form in nano-Cu2Se included composites. Heating microscopy and the heat capacity measurement indicate that the thermal stability of Ag2Se is enhanced with increasing nano-Cu2Se inclusions. The sign of the Seebeck coefficient, in agreement with the Hall coefficient, shows that electrons are the dominant carriers in all samples. The electrical conductivity of the samples increases and the Seebeck coefficient decreases with increasing amount of the nano-Cu2Se inclusion, likely due to augmented carrier concentration. Despite the larger electrical conductivity, the thermal conductivity is suppressed with nano-Cu2Se inclusions. A high power factor and reduced thermal conductivity lead to a maximum ZT value of 0.45 at 875 K for (Ag2Se)(1-x)(nano-Cu2Se)(x) sample where x is 0.05.