We have evaluated thermal stability and aging property of a blue color-emitting phosphor, CaAl2Si2O8:Eu2+ (CAS:Eu2+), synthesized by conventional solid-state reaction method. When both CAS:Eu2+ and BaMgAl10O19:Eu2+ (BAM) were baked in air at 500 degrees C for 20 min. the decrease of photoluminescence (PL) intensity of CAS:Eu2+ was lower than that of BAM. The aging property of CAS:Eu2+ was also better than that of BAM. Due to its rigid Structure and unlimited framework of silicon-oxygen and aluminum-oxygen around Eu2+ ions, Eu2+ ions were protected from outer oxidizing atmosphere and plasma discharge. After analysis of aging property and thermal stability, the differences of these thermal stability and aging property of CAS:Eu2+ from those of BAM were ascribed to its crystal structure which plays a role of a shield for Eu2+ ions against oxidation atmosphere and Xe ion bombardment. (c) 2005 Elsevier Ltd. All rights reserved.