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

Abstract

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 Y₃Al_5−XGa_xO₁₂: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.