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Site Occupancy and Near‐Infrared Luminescence in Ca3Ga2Ge3O12: Cr3+ Persistent Phosphor

The near‐infrared (NIR) luminescence properties of Cr3+ activated Ca3Ga2Ge3O12 (CGGG) are studied under ultraviolet and visible light excitation. Three types of Cr3+ centers associated with 4T2–4A2 transition resulting in the emissions located at 650–1100 nm are identified in all Cr3+‐doped samples. Thanks to the occupancy of three nonequivalent sites in CGGG, NIR luminescence is observed peaking at about 749, 803, and 907 nm, respectively. The influence of crystal field on site occupancy is studied, the relation between site occupancy and the NIR luminescence is addressed, and the energy transfer process among Cr3+ sites and the decay behaviors for Cr3+ in different sites are evaluated. It is found that a superior NIR/persistent luminescence comes from the traps that Cr3+ enters the Ga3+ site. The results are of benefit to investigate Cr3+‐activated persistent phosphors.