Synthesis, crystal structure, spectrum properties, and electronic structure of a new barium aluminoborate, Ba 8[(Al 6IV)(Al 2IV)(Al 2V)B 12IIIO 41] ∞

Abstract

A new barium aluminoborate, Ba 8[(Al 6 IV)(Al 2 IV)(Al 2 V)B 12 IIIO 41] ∞, has been prepared by solid state reaction method below 770 °C, with adding Bi 2O 3 as a flux. Single-crystal XRD analysis showed that it crystallizes in the triclinic space group P 1 ¯ with a = 9.2437(11) Å, b = 9.8100(12) Å, c = 11.0830(14) Å, α = 76.130(10)°, β = 73.550(9)°, γ = 77.990(10)°, Z = 1. The crystal structure contains Latin capital H letter shaped Al 6O 19 20− groups built up from six corner-sharing AlO 4 tetrahedra. The Al 6O 19 20− groups, AlO 4 tetrahedra, AlO 5 trigonal bipyramids, and BO 3 triangles are linked to form a two-dimensional [ ( A l 6 IV ) ( A l 2 IV ) ( A l 2 V ) B 12 III O 41 ] 16 − layer by sharing O vertices. The layers are stacked along the c-axis, with the interlayer void spaces and intralayer open channels occupied by Ba 2+ cations to balance charge. The IR spectrum further confirmed the presence of BO 3 groups. UV–Vis diffuse reflectance spectrum showed a band gap of about 3.10 eV. Solid-state fluorescence spectrum exhibited a broad emission band at around 430 nm. Band structure calculations indicated that it is a direct band material with the calculated band gap (3.25 eV) close to the observed one.