BaSi2O2N2:Eu2+ (Ba1-xEuxSi2O2N2) phosphor was prepared by a method using Ba2SiO4:Eu2+ as a precursor with a starting composition of (Ba1-xEux)(2)Si1-uO4-2u:Si3N4 = 1/2:(3 + u)v/6 (x = 0-0.1, u = 0-0.05, v = 1-1.05). The formation behavior of BaSi2O2N2:Eu2+ and secondary phases was investigated in detail by means of X-ray diffraction analysis of the samples prepared under various conditions. The formation of secondary phases was suppressed by the method employed in this work and a single phase of BaSi2O2N2:Eu2+ was successfully obtained when the starting compositions with x = 0-0.7, u = 0.05, and v = 1.05 were used. BaSi2O2N2:Eu2+ phosphors showed the bluish-green emission peaking at 490-500 nm along with varying concentrations of Eu2+ from 1 to 10 mol % (x = 0-0.1); particularly, the BaSi2O2N2:Eu2+ (5 mol %, x = 0.05) phosphor showed an exceedingly strong emission peak intensity, which was about 3.7 times higher than that of the commercial yellow phosphor, (Y,Gd)(3)Al5O12:Ce3+ (P46-Y3), under 460 nm excitation light. Furthermore, this phosphor maintained luminescence intensity at 150 degrees C by 75% of the value measured at room temperature. These excellent luminescence properties and small thermal quenching suggested this phosphor to be applied as a bluish-green component for phosphor conversion white light-emitting diodes. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3479763] All rights reserved.