Syntheses, structural variants and characterization of A2ZnSn3S8 (A = Cs, Rb) and A2CdSn3S8 (A = Cs, Rb, K, Na) compounds

Abstract

New quaternary A2MSn3S8 (A ​= ​alkali metals; M ​= ​Zn, Cd) sulfides were synthesized and characterized by X-ray diffraction and spectroscopic methods. α-Cs2ZnSn3S8(1), α-Rb2ZnSn3S8(2) and α-Cs2CdSn3S8(3) have layered tetrahedral [MSn3S8]2- frameworks, in which Zn2+, Cd2+ and Sn4+ ions are ordered. No such ordering is present in three-dimensional tetrahedral [MSn3S8]2- framework of β-Cs2ZnSn3S8(4), β-Rb2ZnSn3S8(5), β-Cs2CdSn3S8(6) and β-Rb2CdSn3S8(7) compounds. The β-modifications undergo thermal transformation to α–modifications. K2CdSn3S8(8) and Na2CdSn3S8(9) have a new type of layered structure, in which Cd2+ and Sn4+ ions are octahedrally coordinated and disordered in [CdSn3S8]2- framework. Their potassium and sodium ions undergo facile ion-exchange with mono-, di- and trivalent cations at room temperature. The Raman spectra and band gap values of compounds 1–9 corroborate their structural differences.