Quaternary Sulfide Ba₆Zn₆ZrS₁₄: Synthesis, Crystal Structure, Band Structure, and Multiband Physical Properties

Abstract

Ba6Zn6ZrS14 was synthesized by a traditional salt-melt method with KI as flux. The pale yellow crystals of Ba6Zn6ZrS14 crystallize in the tetragonal space group I4/mcm with a=16.3481 (4) Å and c=9.7221(6) Å. The structure features unique one-dimensional parallel [Zn6S9](6-) and [ZrS5](6-) straight chains. The D2h-symmetric [Zn6S9](6-) cluster serves as the building block of the [Zn6S9](6-) chains. A powder sample was investigated by X-ray diffraction, optical absorption, and photoluminescence measurements. The compound shows multiple-absorption character with three optical absorption edges around 1.78, 2.50, and 2.65 eV, respectively, which are perfectly consistent with the results of first-principles calculations. Analysis of the density of states further revealed that the three optical absorption bands are attributable to the three S(3p(6))→Zr(4d(0)) transitions due to the splitting of the Zr 4d orbitals in the D4h crystal field. The multiband nature of Ba6Zn6ZrS14 also results in photocatalytic activity under visible-light irradiation and three band-edge emissions.