Pb2Al2B3O8F3: structure and properties of a new fluoroaluminoborate with non-traditional chain-like B3O8 groups

Abstract

A new fluoroaluminoborate, Pb₂Al₂B₃O₈F₃, with a non-traditional chain, [B₃O₈]⁷⁻, was synthesized by high temperature reactions in closed systems for the first time. Different from the traditional [B₃O₈]⁷⁻ ring [(3:Δ + 2T)], the [B₃O₈]⁷⁻ in Pb₂Al₂B₃O₈F₃ is chain-like [(3:2Δ + T)]. In the structure, the chain-like [B₃O₈]⁷⁻ group bonds with [AlO₄F₂]⁷⁻ polyhedra to form the [AlB₃O₁₀F₂]⁸⁻ cluster, and the cluster further interconnects to form a three-dimensional framework. The effect of cations on B–O configuration was explored by analyzing available aluminum borates to provide a useful reference for the synthesis of new aluminoborate or fluoroaluminoborate. In addition, first-principles calculations were performed to investigate the relationship between the crystal structure and the optical properties.