Enhanced thermoelectric properties of p-type SnS0.2Se0.8 solid solution doped with Ag

SnS0.2Se0.8 is a naturally abundant, eco-friendly, and low-cost thermoelectric semiconductor. However, less progress has been achieved for the property enhancement as well as the preparing technologies. P-type SnS0.2Se0.8 and Sn0.995Ag0.005S0.2Se0.8 polycrystals were synthesized via combining mechanical alloying (MA) and spark plasma sintering (SPS), and their thermoelectric properties were investigated along the direction perpendicular to the SPS-pressurizing direction. The highest figure of merit (ZT) of ∼0.76 at 823 K was obtained for undoped SnS0.2Se0.8 sample sintered at 813 K. To further optimize the electrical transport properties, Ag element as an acceptor was doped into SnS0.2Se0.8. It was found that 0.5% Ag doping significantly enhanced the power factor from ∼4.12 μW/cm K2 to ∼5.31 μW/cm K2, accompanied by a simultaneous reduction of thermal conductivity at high temperatures. As a result, a high ZT up to ∼1.1 was obtained in Sn0.995Ag0.005S0.2Se0.8, which is 45% higher than that of undoped counterpart.