CsCu3SbS4: rational design of a two-dimensional layered material with giant birefringence derived from Cu3SbS4

Abstract

It is an important and challenging task to develop new infrared (IR) birefringent materials to promote the development of laser technology. In this work, a novel thioantimonate with the highest Cu-to-Sb ratio in the quaternary X/Cu/Sb/Q (X = cations; Q = chalcogen) system, namely CsCu₃SbS₄, was structurally designed and prepared by the strategy of alkali metal introduction into known Cu₃SbS₄. Interestingly, CsCu₃SbS₄ has novel two-dimensional anionic [Cu₃SbS₄]⁻ layers formed by the unprecedented one-dimensional [Cu₃S₃S_3/2]⁶⁻ chains and discrete [SbS₃]³⁻ clusters. Meanwhile, compared with the prototype Cu₃SbS₄, CsCu₃SbS₄ realizes an enormous birefringence boost from 0 to 0.232, which was confirmed by both experimental results and theoretical calculations. This study enriches the sources of thioantimonates and sheds more light on the structure–property relationships of IR birefringent materials.