Fabrication and properties of Bi2−xAg3xS3 thermoelectric polycrystals

Bi2−xAg3xS3 (x = 0–0.06) polycrystals were fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). The phase, microstructure, electrical and thermal transport properties were investigated with a special emphasis on the influence of Ag doping content. All the Bi2−xAg3xS3 powders can be indexed as single phase with an orthorhombic symmetry, a second AgBi3S5 phase in SPSed bulks occurs as the doping contents x ≥ 0.02, which enhances the electrical conductivity, resulting in improvement of electrical transport properties for Bi2−xAg3xS3 bulk samples. A maximum ZT value reached 0.23 at 573 K for the Bi1.99Ag0.03S3 sample, which is 130% higher than that (0.11) of the pure Bi2S3.

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► Bi2−xAg3xS3 (x = 0–0.06) bulks were fabricated by mechanical alloying and spark plasma sintering techniques.
► Ag enters into Bi2S3 lattice interstice when x = 0.01 and a second AgBi3S5 phase appears as x ≥ 0.02.
► The conductive second phase AgBi3S5 could enhance the electrical transport properties of samples
► A peak ZT value reached 0.23 at 573 K for the Bi1.99Ag0.03S3 sample.