Exploratory Synthesis in Molten Salts: Role of Flux Basicity in the Stabilization of the Complex Thiogermanates Cs4Pb4Ge5S16, K2PbGe2S6, and K4Sn3Ge3S14

The influence of the Lewis basicity of alkali polysulfide fluxes (A2Sx) (A = alkali) as a function of x on the respective reactivities of Pb and Sn with Ge was studied and found to be strong. Cs4Pb4Ge5S16, K2PbGe2S6, and K4Sn3Ge3S14 could be prepared only under low basicity with S/A2S ratios of =>11. These compounds display complex frameworks and are semiconductors. Cs4Pb4Ge5S16 is luminescent with red emission.