“…Orange-red persistent luminescence based on the Mn 2+ emission has been observed from MgSiO 3 : Mn 2+ ,Eu 2+ ,Dy 3+ (λ em = 660 nm) [4], MgGeO 2.88 F 0.24 :Mn 2+ , Yb 2+ (670 nm) [5], -Zn 3 (PO 4 ) 2 :Mn 2+ ,M 3+ (M = Al, Ga) (616 nm) [6], and CdSiO 3 :Mn 2+ (575 nm) [7]. Other materials with red persistent luminescence include CaTiO 3 :Pr 3+ [8], Y 2 O 3 :Eu 3+ ,Ti 4+ ,Mg 2+ [9], and Y 2 O 2 S:Sm 2+ [10].…”