Luminescence properties of MAl12O19:Mn4+ (M = Ca, Sr, Ba) for UV LEDs

The luminescence properties of Mn4+-aCtivated MAl12O19 (M = Ca, Sr, Ba) were studied. The Mn4+-activated MAl12O19 compounds were synthesized in an air atmosphere for oxidation from Mn2+ to Mn4+center dot Mn4+-activated CaAl12O19 and SrAl12O19 materials could be excited under the UV region but Mn4+-activated BaAl12O19 materials could not be efficiently emitted under the UV region. The luminescence properties of the Ba-containing compounds deviated from the other compounds, which was attributed to different co-ordinations of the activator ions. Mn4+-activated CaAl12O19 and SrAl12O19 compounds exhibited a main emission peak at 658 nm because of the E-2 ->(4)A(2) transition of the Mn4+ ion. The CaAl12O19 and SrAl12O19 phosphors had a hexagonal structure. The highest crystallinity and luminescent intensity of these phosphors were obtained at 1873 K for 3 h. (C) 2009 The Ceramic Society of Japan. All rights reserved.