Solvothermal syntheses, characterizations and semiconducting properties of four quaternary thioargentates Ba2AgInS4, Ba3Ag2Sn2S8, BaAg2MS4 (M = Sn, Ge)

Abstract

Four quaternary silver sulfides, Ba2AgInS4 (1), Ba3Ag2Sn2S8 (2), BaAg2MS4 (M = Sn for 3; Ge for 4) have been synthesized solvothermally in the presence of excess sulfur as mineralizer. Compound 1 features a 2-D [AgInS4]4−∞2 layer structure composed of AgS4/InS4 tetrahedra, in which the two metals randomly occupy one crystallographic unique position with the molar ratio of 1:1. Compound 2 possesses a 3-D [Ag2Sn2S8]6- framework which constructed by alternative arrangements between AgS4 and SnS4tetrahedra by sharing vertexes. The structures of compounds 3 and 4 are similar and exhibit 3-D anionic [Ag2MS4]2- (M = Sn for 3; Ge for 4) framework composed of AgS2 layers and monomeric MS4 (M = Sn, Ge) tetrahedra that pillar the above layers. Moreover, semiconducting properties (optical bandgap, photoelectric response) of the title compounds were also investigated. The results indicate that all the quaternary sulfides are narrow-gap semiconductors, and compound 3 exhibits excellent photocurrent responsive property.