Simple Aliovalent Cation Substitution to Induce Strong Optical Anisotropy Enhancement in Rare Thioantimonates (V) Family

Abstract

Thioantimonates containing high oxidation state Sb5+ have proven to exhibit excellent performance in the design of new materials such as infrared optics crystals and lithium-ion batteries. However, as described by the “inert pair effect”, the preparation of P-block elements containing high oxidation states in sealed systems have been a challenge. In this study, an aliovalent cation substitution strategy was used to design and synthesize three novel thioantimonates (V), respectively A4BaSb2Se8 (A = Cs, Rb) and Rb2BaSbS4Cl (RBSSC), which all contain rare [SbS4] tetrahedral units. The introduction of Ba2+ ion leads to the distortion and high-density arrangement of [SbSe4] units, which is manifested as a significant 3.7 times enhancement of the birefringence compared to the parent compound Cs3SbSe4 (0.041→0.150@1064 nm). By further introducing highly electronegative halogen atoms, the first antimony-based thiohalides (V) RBSSC was synthesized. Theoretical calculations show that the band gap of RBSSC is up to 3.674 eV, lager than those of all known antimony-based thiohalides (III). This work provides a strong evidence that the aliovalent cation substitution strategy is an effective way to find new thioantimonates (V) families, and also indicates that the cation size effect introduced by elements substitution may lead to surprising performance improvements.