Defects in BaMgAl10O17: Eu2+ Blue Phosphor

The luminescent properties of BaMgAl₁₀O₁₇: Eu²⁺ blue phosphor are closely related to the valence state of europium inside the crystal and its defect structure. Because of the complexity of the BAM structure, research was carried out to study the europium-related defects by computer simulation. Two different Mg distributions were found to have the same lattice energy, but the arrangement of Mg affected the defect energy and Eu position. Eu³⁺ behavior was also discussed to address the oxidation-induced luminescent degradation. Two energetically most-favorable positions were found for europium, depending on the oxidation state: the Beevers-Ross site on the conduction plane for Eu²⁺, and the Al(2) site in the middle of the spinel block for Eu³⁺. Results of defect complex and bond-valence calculations suggested that the large europium ion can reside in the oxygen close-packed spinel blocks. A comparison of europium defect properties calculated with two different potential models suggests that results of the simulations are potential independent.