Combined Rietveld refinement of BaMgAl 10O 17:Eu 2+ using X-ray and neutron powder diffraction data

Abstract

The phosphor, BaMgAl 10O 17:Eu 2+, showing a blue emission band at about 450 nm was prepared by a normal solid-state reaction using BaCO 3, Al 2O 3, MgO and Eu 2O 3 as starting materials with AlF 3 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, Eu 2+(1.09 Å) and Ba 2+(1.34 Å), compared with those of BaMgAl 10O 17.