Alkali halide flux synthesis, crystal structure, and photoelectric response of quaternary thiosilicates K₃Ga₃Si₇S₂₀ and K₂ZnSi₃S₈

Two new quaternary thiosilicate crystalline compounds namely K3Ga3Si7S20 (1) and K2ZnSi3S8 (2) with distinct dimensions were successfully synthesized by the alkali halide flux synthesis method. Both structures feature an anionic M-S-Si (M = Ga or Zn) network constructed from interconnected MS4 and SiS4 tetrahedral units with charge balancing K+ cations. The anionic architecture of 1 is a three-dimensional (3-D) anionic open framework of [(Ga/Si)(10)S-20](n)(3n-) with large channels in which K+ ions are located, while that of 2 presents a two-dimensional (2-D) anionic layer of [ZnSi3S8](n)(2n-) and K+ cations reside in the interlayered spaces. Their physicochemical performances including optical bandgap and thermal behavior were investigated, and the photoelectric response and impedance of 1 were explored. The optical absorption edges of the two compounds are determined to be 3.60 eV (1) and 2.57 eV (2), respectively. In particular, 1 shows good photoelectric response performance, which endows it with broad application prospects in the photoelectric field.