Liquid-Phase Manipulation Securing Enhanced Thermoelectric Performance of Ag₂Se

Developing n-type materials with high peak and/or average ZT (ZT is the figure of merit) is an urgent need for the lower ZT of the existing n-type BiTeSe materials compared with the p-type BiSbTe materials. Here, we demonstrate that liquid-phase sintering can lead to lowered thermal conductivity and an improved power factor in n-type Ag2Se, which originates from the greatly lowered electronic thermal conductivity attributed to the decreased mobility and improved Seebeck coefficients because of increased effective mass. Benefiting from this, the maximum ZT (ZTmax) of ∼1.21 and the average ZT (ZTave) of 1.06 are successfully achieved in polycrystalline Ag2Se. In this work, ZTave is the highest reported value, being 26% larger than that of Ag2Se reported. Our work shows that liquid-phase sintering to achieve improved thermoelectric (TE) performance opens a great opportunity for designing prospective thermoelectrics.