BaMgAl10O17:Eu2+ phosphor (BAM:Eu2+) is a useful blue phosphor for plasma display panel (PDP) and fluorescent lamps, but is liable to be degraded by vacuum ultraviolet (VUV) irradiation. We found that YAl3(BO3)(4):Gd3+ phosphor (YAB:Gd3+) has a high efficiency of emission at 313 nm under VUV excitation and strong resistance to luminescence degradation caused by heat and VUV irradiation. To prevent this degradation, YAB:Gd3+ is mixed with BAM:Eu2+. In this mixed phosphor, the VUV energy absorbed by the former is efficiently transformed to the blue emission of the latter. Consequently, the luminescence degradation inherent in the blue phosphor is decreased with a small sacrifice of the emission intensity. (C) 2003 The Electrochemical Society.