Combined Rietveld refinement of BaMgAl10O17:Eu2+ using X-ray and neutron powder diffraction data

The phosphor, BaMgAl10O17:Eu2+, showing a blue emission band at about 450 nm was prepared by a normal solid-state reaction using BaCO3, Al2O3, MgO and Eu2O3 as starting materials with AlF3 as a flux. The study of combined Rietveld refinement and photoluminescence spectra was carried out to determine the structural parameters, such as lattice constants, the valence state of Eu, the site preference of Mg and site fractions of Mg and Eu. The occupancies of Eu and Mg were 0.022 and 0.526, respectively. The valence state of Eu was the divalent state because there was only one broad line at about 450 nm in the photoluminescence spectrum. The site preference of Mg atoms was the tetrahedral site of Al atoms surrounded by oxygen atoms in the spinel block. Lattice parameters decreased due to the difference of two ionic radii, Eu2+(1.09 Å) and Ba2+(1.34 Å), compared with those of BaMgAl10O17.