Synthesis, crystal structure, spectrum properties, and electronic structure of a new barium aluminoborate, Ba8[(Al6IV)(Al2IV)(Al2V)B12IIIO41]∞

Graphical abstract: The crystal structure of Ba8[(Al6IV)(Al2IV)(Al2V)B12IIIO41]∞ is composed of Latin capital H letter shaped Al6O1920- groups, AlO4 tetrahedra, AlO5 trigonal bipyramids, and BO3 triangles that are linked to form a two-dimensional [(Al6IV)(Al2IV)(Al2V)B12IIIO41]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 Ba2+ cations to balance charge. Highlights: → Ba8[(Al6IV)(Al2IV)(Al2V)B12IIIO41]∞ has been prepared by solid state reaction method. → It has a layered structure consisting of Latin capital H letter shaped Al6O1920- groups, AlO4 tetrahedra, and AlO5 trigonal bipyramids bridged by BO3 triangles. → The IR spectrum confirmed the presence of BO3 groups. Band structure calculations indicated that it is a direct band material with the calculated band gap (3.25 eV) close to the observed one (3.10 eV). - Abstract: A new barium aluminoborate, Ba8[(Al6IV)(Al2IV)(Al2V)B12IIIO41]∞, has been prepared by solid state reaction method below 770 deg. C, with adding Bi2O3 as a flux. Single-crystal XRD analysis showed that it crystallizes in the triclinic space group P1-bar with a = 9.2437(11) A, b = 9.8100(12) A, c = 11.0830(14) A, α = 76.130(10)o, β = 73.550(9)o, γ = 77.990(10)o, Z = 1. The crystal structure contains Latin capital H letter shaped Al6O1920- groups built up from six corner-sharing AlO4 tetrahedra. The Al6O1920- groups, AlO4 tetrahedra, AlO5 trigonal bipyramids, and BO3 triangles are linked to form a two-dimensional [(Al6IV)(Al2IV)(Al2V)B12IIIO41]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 Ba2+ cations to balance charge. The IR spectrum further confirmed the presence of BO3 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.