Ba₃Ga₃N₅—A Novel Host Lattice for Eu²⁺-Doped Luminescent Materials with Unexpected Nitridogallate Substructure

Abstract

The alkaline earth nitridogallate Ba 3 Ga 3 N 5 was synthesized from the elements in a sodium flux at 760 °C utilizing weld shut tantalum ampules. The crystal structure was solved and refined on the basis of single-crystal X-ray diffraction data. Ba 3 Ga 3 N 5 (space group C 2/ c (No. 15), a = 16.801(3), b = 8.3301(2), c = 11.623(2) Å, β = 109.92(3)°, Z = 8) contains a hitherto unknown structural motif in nitridogallates, namely, infinite strands made up of GaN 4 tetrahedra, each sharing two edges and at least one corner with neighboring GaN 4 units. There are three Ba 2+ sites with coordination numbers six or eight, respectively, and one Ba 2+ position exhibiting a low coordination number 4 corresponding to a distorted tetrahedron. Eu 2+ -doped samples show red luminescence when excited by UV irradiation at room temperature. Luminescence investigations revealed a maximum emission intensity at 638 nm (FWHM =2123 cm –1 ). Ba 3 Ga 3 N 5 is the first nitridogallate for which parity allowed broadband emission due to Eu 2+ -doping has been found. The electronic structure of both Ba 3 Ga 3 N 5 as well as isoelectronic but not isostructural Sr 3 Ga 3 N 5 was investigated by DFT methods. The calculations revealed a band gap of 1.53 eV for Sr 3 Ga 3 N 5 and 1.46 eV for Ba 3 Ga 3 N 5 .