SrAl_2-Li₂₊O₂₊₂N_2-2:Eu²⁺ (0.12 ≤ x ≤ 0.66)-Tunable Luminescence in an Oxonitride Phosphor

Starting from the recently published narrow band red phosphor SALON, a tunable oxonitride-phosphor can be derived by introducing disorder into the structure. To achieve this, the oxygen content of the reaction mixture is increased, thereby prohibiting the oxygen/nitrogen ordering observed in SALON. The resulting compound is isotypic to UCr₄C₄ and exhibits mixed oxygen/nitrogen and lithium/aluminum sites. Further variation of the oxygen/nitrogen ratio revealed that the structure remains stable over a wide range of compositions. The compound can therefore be described by the general sum formula SrAl_2-Li₂₊O₂₊₂N_2-2 with x ranging between 0.12 and 0.66. When doped with Eu²⁺, the title compound exhibits an intense luminescence upon excitation with blue light. The maximum of this emission varies depending on the oxygen content and can be tuned to values between 581 nm (x = 0.66) and 672 nm (x = 0.12).