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

Abstract

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)₁₀S₂₀]_n³ⁿ⁻ with large channels in which K⁺ ions are located, while that of 2 presents a two-dimensional (2-D) anionic layer of [ZnSi₃S₈]_n²ⁿ⁻ 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.