Luminescence properties of (Sr_0.95-x-yMg_xY _y)Si₂O_2-yN_2+y:Eu²⁺ _0.05 for novel LED conversion phosphors

By incorporating Mg and Y into SrSi₂O₂N ₂:Eu²⁺ phosphor, we intended to improve the relatively high thermal quenching and poor efficiency of emission in conventionalSrSi ₂O₂N₂:Eu²⁺ phosphors. MSi ₂O₂N₂:Eu²⁺ _0.05 (M = Sr, Mg, Y) compounds were synthesized by ahigh-temperature solid-state reactionand were characterized using X-ray power diffraction as well as excitation and emission spectroscopy. As compared to the pure SrSi₂O ₂N₂:Eu²⁺ _0.05, the emission intensity of the new MSi₂O₂N₂:Eu²⁺ _0.05 (M = Sr, Mg, Y) compound was increased by 65 %. Meanwhile, it was also possible to improve the ratio of thermal quenching up to 88 % by substituting the Sr with Mg and/or Y in the SrSi₂O₂N ₂:Eu²⁺ _0.05 crystal structure. This improvement was mainly due to the intrinsic electronic negativity and size effect of Y ³⁺, which leads to the shrinkage of the O/N ratioand the relaxation of local strain around the Eu²⁺ ion in the (Sr _0.95-x-yMg_xY_y)Si₂O _2-yN_2+y:Eu²⁺ _0.05 structure. Consequently, the (Sr_0.68Mg_0.27)Si₂O ₂N₂:Eu²⁺ _0.05 phosphor is expected to be useful as a novel conversion phosphor with high thermal stability for white-light LEDs.