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) A and c=11.6192(2) A) 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 [ ∞ 2 Zn S 3 / 3 O 1 / 1 ] . Heat capacity measurements reveal that the room-temperature structure of SrZnSO persists down to 2 K. From optic data, a band-gap of about 3.1 eV 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.