Oxonitridosilicate phosphors with compositions of Y 1-x Ce x SiO 2 N (x=0-0.1) were synthesized by a new synthetic route based on a solid state reaction among YSi, CeSi, SiO 2 and Y 2 O 3 compounds at high temperature and high pressure. The photoluminescence properties dependent on Ce concentration and temperature were investigated. Concentration quenching occurred when the doped Ce 3+ concentration was more than 3 mol.%. The emission spectra showed red shifts from 430 to 447 nm with the increased Ce concentration from 0.5 mol.% to 10 mol.%. The quenching temperature was estimated as ～380 K. The chromaticity coordinates of the excitation and emission spectra were stable against the temperature. This study showed these YSiO 2 N:Ce 3+ phosphors the potential applications in the three-RGB phosphor-converted white LEDs. Oxonitridosilicate phosphors with compositions of Y 1-x Ce x SiO 2 N (x = 0-0.1) were synthesized by a new synthetic route based on a solid state reaction among YSi, CeSi, SiO 2 and Y 2 O 3 compounds at high temperature and the high pressure. Concentration quenching occurred when the doped Ce 3+ concentration was more than 3 mol.%. The emission spectra showed red shifts from 430 to 447 nm with the increased Ce concentration from 0.5 mol.% to 10 mol.%. The quenching temperature was estimated as ~ 380 K. The chromaticity coordinates of the excitation and emission spectra were stable against the temperature. This study showed these YSiO 2 N: Ce 3+ phosphors the potential applications in the three-RGB phosphor-converted white LEDs.