A2SbB3O8 (A = Na, K, Rb) and β-RbSbB2O6: two types of alkali boroantimonates with 3D anionic architectures composed of SbO6 octahedra and borate groups

Abstract

Four new alkali metal boroantimonates, namely, A₂SbB₃O₈ (A = Na, K, Rb) and β-RbSbB₂O₆, have been synthesized by high-temperature solid-state reactions. Isostructural A₂SbB₃O₈ (A = Na, K, Rb) crystallizes in the monoclinic space group P2₁/c, with structures featuring a novel 3D anionic framework composed of SbO₆ octahedra and linear B₃O₈ groups with 1D tunnels of Sb₄B₄ 8-membered-rings (MRs) along the a-axis, which are filled by alkali metal ions. β-RbSbB₂O₆ crystallizes in the polar space group Cc, revealing novel 3D anionic networks composed of SbO₆ octahedra chains and B₂O₅ groups with 1D tunnels of Sb₄B₂ 6-MRs along the b-axis and 1D tunnels of Sb₃B₄ 7-MRs along the c-axis. Studies on their optical properties and thermal stability, band structure calculations based on DFT methods and linear optical calculations have also been performed.