Synthesis and characterization of sulfide oxide SrZnSO with strongly polar crystal structure

Abstract

Pure SrZnSO powder is successfully prepared from repeated reactions at 1050°C followed by a water sonication treatment. The final product has a light green color. Crystallites are optically transparent and crystal structure investigations reveal that SrZnSO crystallizes in a non-centrosymmetric, polar, hexagonal space group (P63mc, a=3.90442(6)Å and c=11.6192(2)Å) and is isostructural to CaZnSO. The crystal structure of SrZnSO has polar layers in the ab plane of S-vertex-sharing ZnS3O tetrahedra that are separated by Sr ions: the complete structure can be written as Sr[∞2ZnS3/3O1/1]. Heat capacity measurements reveal that the room-temperature structure of SrZnSO persists down to 2K. From optic data, a band-gap of about 3.1eV is estimated and further absorption bands indicate defects in the anion lattice. Calculations based on atom fractional coordinates suggest that SrZnSO is less polar than CaZnSO.