Crystal field modulation-control, bandgap engineering and shallow/deep traps tailoring-guided design of a color-tunable long-persistent phosphor (Ca, Sr)Ga4O7:Mn2+,Bi3+ .

In this paper, a new color tunable long persistent phosphor (Ca, Sr)Ga4O7:Mn2+,Bi3+ has been successfully synthesized via a high-temperature solid-state reaction. Crystal field modulation and band gap engineering controlled by Sr2+ substitution for Ca2+ realizes the color tunable Mn2+ emission from 580 to 556 nm. Guided by the tailoring of traps distribution, the long persistence luminescence (LPL) performance of CaGa4O7:Mn2+ is greatly enhanced to 33 times higher brightness and much longer persistent time through Bi3+ co-doping. Furthermore, aided by the Rietveld refinement method, steady/transient-state fluorescence and thermoluminescence (TL) techniques with the combination of DFT calculations, the crystal structure evolution, electronic structure, trap distribution tailoring, self reduction of Mn4+, and the related color tunable Mn2+ photoluminescence/enhanced LPL properties are systematically characterized. Finally, a schematic diagram is proposed for a detailed illustration of the photoluminescence and LPL mechanisms.