Vacuum Annealing Effects on the Transport and Thermoelectric Properties of the Novel Layered Bi-chalcogenide LaOBiSnS3

The impact of annealing on the transport and thermoelectric properties of the novel layered Bi-chalcogenide LaOBiSnS3 is investigated. Electrical transport measurements show that annealing strongly suppresses the resistivity, and that a single thermally activated conduction model is no longer sufficient to describe the low-temperature transport. Hall-effect measurements indicate that the resistivity reduction is dominated by a pronounced enhancement of carrier mobility, while the carrier concentration increases only moderately. At higher temperatures (300-773 K), the thermoelectric figure of merit ZT is significantly improved, reaching approximately 0.20 at 773 K for the annealed sample. These findings suggest that post-annealing treatment is an effective route to enhance the thermoelectric performance of BiS2-based layered materials, primarily by improving carrier mobility.