Investigation of luminescence quenching and persistent luminescence in Ce3+ doped (Gd,Y)3(Al,Ga)5O12 garnet using vacuum referred binding energy diagram

Optical properties of Ce3+:5d−4f luminescence in garnet compounds are strongly related to the energy locations of the excited 5d levels and the host conduction band (CB). By constructing the vacuum referred binding energy (VRBE) diagram including information on these energy location for GdyY3-yAl5-xGaxO12 garnet (GYAGG) from the measured spectroscopic data, the luminescence quenching and persistent luminescence properties of GYAGG:Ce3+(-Cr3+) were discussed. The quantum yield (QY) of Ce3+:5d−4f in GYAGG:Ce3+ is clearly related to the energy gap, ΔE5d1−CB, between the lowest 5d level and the bottom of conduction band in the constructed VRBE diagram. This result indicates that the luminescence quenching of GYAGG:Ce3+ is caused by the thermal ionization. For GYAGG:Ce3+-Cr3+ persistent phosphors, the depth of the electron trap formed by Cr3+ was remarkably changed from 0.27 to 0.69 eV by varying the Gd and Ga contents. The estimated VRBE value of Cr2+ in GYAGG can be used as effective value to predict the electron trap depth by Cr3+ in other oxide compounds as well as garnet hosts.