Mild solvothermal syntheses of thioargentates A-Ag-S (A = K, Rb, Cs) and A-Ag-Ge-S (A = Na, Rb): crucial role of excess sulfur.

A series sulfides of A-Ag-S (1-3; A = K, Rb, Cs), Na5AgGe2S7 (4), and Rb2Ag2GeS4 (5) have been prepared solvothermally in the presence of excess sulfur. Among these compounds, 4 is a new compound that has a novel layered structure; the others were obtained under mild conditions. The results showed that excess sulfur could increase the solubility of silver sulfide and lower the synthetic temperature effectively. The mineralizer effect of excess sulfur is discussed in detail.