Identifying a Cyan Ultralong Persistent Phosphorescence (Ba, Li) (Si, Ge, P)₂O₅:Eu²⁺, Pr³⁺ via Solid Solution Strategy

A series of cyan emission (Ba, Li) (Si, Ge, P) 2 O 5:Eu 2+, Pr 3+ long persistent phosphors (LPP) were designed by solid solution strategy and synthesized by solid-state reaction; the crystal structure and photoluminescence of this long persistent phosphor have been analyzed systematically. Under 256 nm light excitation, the as-prepared (Ba, Li) (Si, Ge, P) 2 O 5:Eu 2+, Pr 3+ presents a strong cyan emission located at 514 nm, and the decay time of samples can be extended to about 38 h (BaSi 2 O 5:0.008Eu 2+, 0.01Pr 3+ ), 47 h (BaSi 1.5 Ge 0.5 O 5:0.008Eu 2+, 0.01Pr 3+ ), and 56 h (Ba 0.92 Li 0.08 Si 1.92 P 0.08 O 5:0.008Eu 2+, 0.01Pr 3+ ) after ceasing the excitation source. A number of excitation duration (1 s ≤ t ≤ 30 s)-, decay duration (10 min ≤ t ≤ 10 h)-, and temperature-dependent thermoluminescence experiments of (Ba, Li) (Si, Ge, P) 2 O 5:0.008Eu 2+, 0.01Pr 3+ were conducted, revealing that the existence of shallow and deep traps caused by Eu 2+ and Pr 3+ ions in samples gives rise to the excellent LPP property. According to the experimental results, a feasible mechanism of persistent luminescence of (Ba, Li) (Si, Ge, P) 2 O 5:0.008Eu 2+, 0.01Pr 3+ was proposed and illustrated in detail.