2+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 SrSi 2 O 2 N 2 :Eu 2+ 0.05 , the emission intensity of the new MSi 2 O 2 N 2 :Eu 2+ 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 SrSi 2 O 2 N 2 :Eu 2+ 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 Eu 2+ ion in the (Sr 0.95-x-y Mg x Y y )Si 2 O 2-y N 2+y :Eu 2+ 0.05 structure.Consequently, the (Sr 0.68 Mg 0.27 )Si 2 O 2 N 2 :Eu 2+ 0.05 phosphor is expected to be useful as a novel conversion phosphor with high thermal stability for white-light LEDs.