Enhanced Thermoelectric Properties of AgSb_1–<i>x</i>Pb_<i>x</i>Bi_<i>y</i>Se₂ Achieved via Microwave Smelting Combined with Spark Plasma Sintering

In this study, two series of thermoelectric (TE) materials, AgSb_1-<i>x</i>Pb_<i>x</i>Se₂ (<i>x</i> = 0.00, 0.035, 0.04, 0.045, and 0.05) and AgSb_0.955Pb_0.045Bi_<i>y</i>Se₂ (<i>y</i> = 0.01, 0.015, 0.02, and 0.025), were fabricated that are achieved via microwave smelting (MS) combined with spark plasma sintering (SPS). Although Pb doping effectively increased the carrier concentration (<i>n</i>) of the AgSb_1-<i>x</i>Pb_<i>x</i>Se₂ materials, it substantially restricted the improvement in carrier mobility (μ_H), leading to a nonsignificant enhancement in the dimensionless figure of merit (ZT). To address this issue, AgSb_1-<i>x</i>Pb_<i>x</i>Se₂ was doped with Bi to optimize <i>n</i> and μ_H. The phase composition, microstructure, and electrical and thermal transport properties of the materials were characterized in the temperature range of 300-723 K. The AgSb_0.955Pb_0.045Bi_0.025Se₂ material exhibited a maximum power factor of 720 μWK^-2 m^-1 at 723 K and a reduced lattice thermal conductivity of 0.36 Wm^1- K^-1. Consequently, a ZT value as high as 1.23 was obtained at 723 K. This study demonstrates that microwave smelting - SPS is an efficient and environmentally friendly method for the synthesis of Pb- and Bi-doped AgSbSe₂ materials with excellent TE transport properties.