Electronic Structures and Pr3+ Photoluminescence Characteristics in Fresnoite, Sr‐Frenoite, and Ge‐Frenoite

The undoped and Pr 3+ ‐doped Fresnoite (Ba 2 TiSi 2 O 8 ), Sr‐frenoite (Sr 2 TiSi 2 O 8 ), and Ge‐frenoite (Ba 2 TiGe 2 O 8 ) were synthesized by solid‐state reaction at high temperature and their photoluminescence properties and electronic structures were investigated. All these undoped samples show luminescence upon UV irradiation at room temperature. The excitation band of intervalence charge transfer (IVCT) emerged only in Sr 2 TiSi 2 O 8 :Pr 3+ , which was located at 340 nm. Under 340 nm excitation, Sr 2 TiSi 2 O 8 :Pr 3+ showed an efficient red emission at 616 nm, ascribing to the 1 D 2 → 3 H 4 transition of Pr 3+ . However, Pr 3+ red emissions and the excitation band of IVCT were not observed for Ba 2 TiSi 2 O 8 and Ba 2 TiGe 2 O 8 and the possible reasons for such behaviors were discussed.