Exploration of antimony(iii) oxyhalides via single-site substitution in quest of large birefringence

Abstract

Birefringent crystals play a crucial role in the laser polarization of modern laser technologies. As a marvelous branch of optical materials, oxyhalides are attracting extensive interest for their suitable structures and diverse properties. Metal cations with lone pairs have proven advantageous for enhancing birefringence and extending the range of transmission. In this study, we comprehensively investigated the antimony(III) oxyhalide system, Sb–O–X. Specifically, we systematically examined the impact of single-site substitution within a series of compounds, including SbOCl, Sb₂OCl₄, Sb₃O₄F, Sb₃O₄I, Sb₃O₄Cl, Sb₈O₁₁Cl₂, and Sb₈O₁₁Br₂. The substitution of halogens led to significant alterations in the crystal structures, ranging from 0D isolated units to 2D layers, which are favorable for generating birefringences greater than 0.1. These findings underscore the potential of antimony oxyhalides for achieving the balance between birefringence and bandgap, and affirm the viability of single-site substitution as an effective strategy for discovering birefringent materials.