Tunable emission properties of Eu-ion-doped AAl2O4 (A = Ca, Sr, Ba)

초록

A series of AAl2O4:Eu (A = Ca, Sr, and Ba) phosphors was synthesized in bulk and powder forms, and their structural and photoluminescence properties were investigated. X-ray diffraction analysis showed that CaAl2O4: Eu and BaAl2O4:Eu exhibited monoclinic and hexagonal structure, respectively in bulk and powder forms. In contrast, the SrAl2O4:Eu powder exhibited a hexagonal structure, and the SrAl2O4:Eu bulk exhibited a monoclinic structure. Furthermore, structural changes were observed during the post-annealing process depending on the annealing temperature. Photoluminescence studies showed that the valence state of Eu ions could be effectively tuned by the annealing atmosphere and temperature, resulting in significant changes in the emission color. H2 annealing reduced Eu3+ to Eu2+ in the selected samples, and the emission color, calculated using the CIE chromaticity coordinates, could be controlled from reddish violet to purple, red to green, and orange to sky blue. In particular, the luminescence behavior of the SrAl2O4:Eu powder depended on the annealing temperature, which was related to structural changes. These results demonstrate a strong relationship among the crystal structure, Eu valence state, and luminescence, highlighting that controlled thermal and atmospheric treatments provide an efficient strategy for tuning AAl2O4:Eu phosphors for solid-state lighting and phosphor applications.

키워드