Control of electron transfer between Ce3+ and Cr3+ in the Y3Al5-xGaxO12 host via conduction band engineering

Among inorganic compounds doped with lanthanide or transition metal ions for persistent phosphors, the transfer process of the localized electron in the dopant cations to the conduction band (CB) is crucial. In Y3Al5-XGaxO12:Ce3+-Cr3+, we found that the electron produced by photoionization of the Ce3+ ion by UV and blue excitation transfers to the Cr3+ ion through the CB. The electron trapped by Cr3+ is thermally released at different temperatures from 400 K to 150 K in the YAGG host with different Ga content because we managed to decrease the energy gap between the CB and the electron trap by increasing the Ga content. The persistent luminescence mechanism has been explained by constructing the vacuum referred binding energy (VRBE) diagram comprising the Ce3+, Cr2+, valence band (VB) and conduction band (CB) level energies in the YAGG host with different Ga/Al ratios.