Mechanochemical Synthesis of Cu2MgSn3S8 and Ag2MgSn3S8

Two new thiospinels of the type A^I₂B^IIC^IV₃S^VI₈ were successfully synthesized via a mechanochemical route using binary sulfides and sulfur. Cu₂MgSn₃S₈ and Ag₂MgSn₃S₈ are the first A^I₂B^IIC^IV₃S^VI₈ compounds with magnesium as divalent cation. The crystal structures of Cu₂MgSn₃S₈ and Ag₂MgSn₃S₈ were refined in the cubic space group Fd3 m using X-ray powder diffraction. According to UV/Vis measurements, a direct optical bandgap of ca. 1.65 eV was determined for both Cu₂MgSn₃S₈ and Ag₂MgSn₃S₈. Temperature-dependent magnetic susceptibility measurements of the Cu₂MgSn₃S₈ sample indicate diamagnetism. A ¹¹⁹Sn Mössbauer spectrum confirms the tetravalent state of tin, underlining the electron-precise description.