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

Abstract

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⁺. 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 ²E→⁴A₂ 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.