First Evidence of Electron Trapped Ln 2+ Promoting Afterglow on Eu 2+ , Ln 3+ Activated Persistent Phosphor‐Example of BaZrSi 3 O 9 :Eu 2+ , Sm 3+

Abstract BaZrSi 3 O 9 :Eu 2+ , Sm 3+ (Em:525 nm) is prepared. The role played by the trivalent co‐doping ion Sm 3+ in the afterglow and the type of trap are clarified. BaZrSi 3 O 9 :Eu 2+ , Sm 3+ is found to produce Sm 2+ during the excitation by X‐ray absorption near‐edge structure (XANES), etc., and it is thus proved that Sm 3+ exists as an electron trap in the afterglow process. In the field of persistent phosphors activated by Eu 2+ and Re 3+ such as Sm 3+ or Dy 3+ having been widely utilized as emergency guide lights, clock faces, etc. for > 25 years, for the first time it is successfully observed that after excitation Re 2+ is formed, transferring its electron to 5d band of Eu 2+ , returning to Re 3+ by itself, where the decrease in Sm 2+ coincides with the increase in Sm 3+ , and the two decay time τ 1 and τ 2 of PL ( 5 D 0 → 7 F 0 ) of Sm 2+ coincides with the two evolution time of PL (5d→4f) of Eu 2+ . The behavior of electron transfer from Sm 2+ to Eu 2+ as a key of afterglow is detected. The detailed afterglow mechanism is proposed by analysis of thermoluminescence and defect reaction, which is very important for the in‐depth investigation of the long afterglow material and the further improvement of the mechanism.