Trap depth and color variation of Ce3+-Cr3+ co-doped Gd3(Al,Ga)5O12 garnet persistent phosphors

Persistent luminescent properties in Ce3+-Cr3+ codoped Gd3Al5−xGaxO12 garnet (GAGG:Ce-Cr) solid solution have been investigated. The persistent luminescent color is shifted from orange to yellowish green with increasing Ga content because Ce3+: 5d level splitting becomes much weaker. The depth of electron trap introduced by Cr codoping was estimated from the intense thermoluminescence glow peak by the initial rise method. The trap depth decreases from 0.56 eV to 0.29 eV with increasing Ga content. The shift can be explained by downshift of bottom of conduction band. From the persistent luminescence decay curve measurement after ceasing 450 nm blue illumination, the samples with x = 2.5 exhibited the longest persistent luminescence for 405 min until the luminance becomes 2 mcd/m2 in GAGG:Ce-Cr phosphors.