Enhancement of Red Persistent Luminescence in Cr³⁺-Doped ZnGa₂O₄Phosphors by Bi₂O₃Codoping

Bi 2 O 3 was proved to be an effective codopant to enhance red persistent luminescence in Cr 3+ -doped ZnGa 2 O 4 spinel. The Cr–Bi-codoped ZnGa 2 O 4 phosphors showed about 10 times higher persistent luminescence intensity than the Cr-singly-doped phosphors. The radiance (in mW sr -1 m -2 ) of persistent luminescence in ZnGa 2 O 4 :Cr,Bi phosphors was comparable to that in commercialized SrAl 2 O 4 :Eu,Dy phosphors. Increases of Cr 3+ absorption and photoluminescence were also observed in the Cr–Br-codoped ZnGa 2 O 4 sample. The obtained results suggest that Bi 2 O 3 may play a critical role in stabilizing Cr 3+ in ZnGa 2 O 4 spinel.