화학공학소재연구정보센터
Inorganic Chemistry, Vol.55, No.17, 8359-8370, 2016
Eu2+-Activated Alkaline-Earth Halophosphates, M-5(PO4)(3)X:Eu2+ (M = Ca, Sr, Ba; X = F, Cl, Br) for NUV-LEDs: Site-Selective Crystal Field Effect
Eu2+-activated M-5(PO4)(3)X (M = Ca, Sr, Ba; X = F, Cl, Br) compounds providing different alkaline-earth metal and halide ions were successfully synthesized and characterized. The emission peak maxima of the M-5(PO4)(3)Cl:Eu2+ (M = Ca, Sr, Ba) compounds were blue shifted from Ca to Ba (454 nm for Ca, 444 nm for Sr, and 434 nm for Ba), and those of the Sr-5(PO4)(3)X:Eu2+ (X = F, Cl, Br) compounds were red-shifted along the series of halides, F -> Cl -> Br (437 nm for F, 444 nm for Cl, and 448 nm for Br). The site selectivity and occupancy of the activator ions (Eu2+) in the M-5(PO4)(3)X:Eu2+ (M = Ca, Sr, Ba; X = F, Cl, Br) crystal lattices were estimated based on theoretical calculation of the 5d -> 4f transition energies of Eu2+ using LCAO. In combination with the photoluminescence measurements and theoretical calculation, it was elucidated that the Eu2+ ions preferably enter the fully oxygen-coordinated sites, in the M-5(PO4)(3)X:Eu2+ (M = Ca, Sr, Ba; X = F, Cl, Br) compounds. This trend can be well explained by "Pauling's rules". These compounds may provide a platform for modeling a new phosphor and application in the solid-state lighting field.