Cubic Quaternary Silver Chalcogenide: A Promising Ductile Thermoelectric Inorganic

Owing to their superior plastic deformability and tunable electrical and thermal transport properties, semiconducting silver chalcogenides exhibit unique advantages in the application of flexible thermoelectrics. In this work, we report the discovery of ductile Ag2S0.4(Se0.6Te0.4)0.6 with a cubic structure. Due to the alloying effect, the high-temperature body-centered cubic structure is stabilized at room temperature for Ag2S0.4(Se0.6Te0.4)0.6, which is of vital importance for practical applications. The cubic Ag2S0.4(Se0.6Te0.4)0.6 shows plastic deformability comparable to that of α-Ag2S, while the dimensionless thermoelectric figure of merit zT is only ∼0.06 due to its overhigh carrier concentration. A small amount of excessive Se [Ag2S0.4(Se0.6Te0.4)0.6 + ySe (y = 0, 0.02, 0.03, 0.04, 0.05)] is added to reduce the carrier concentration and improve the thermoelectric properties. Owing to the effectively optimized carrier concentration, the thermoelectric power factor of the sample with y = 0.04 reaches 6.2 and 7.5 μW cm–1 K–2 at, respectively, 300 and 350 K, showing promising potential for near-room-temperature applications. Combined with the decreased total thermal conductivity, the zT values of the samples with y = 0.04 and 0.05 reach ∼0.3 at 300 K, which is five times that of Ag2S0.4(Se0.6Te0.4)0.6. This study provides helpful guidance for the design of ductile silver chalcogenide semiconductors with stable and improved thermoelectric properties.