Phosphorescence behavior and photoluminescence mechanism of Dy3+ sensitized β-Zn3(PO4)2: Mn2+ phosphor

A red long persistent phosphor (LPP) of β-Zn3(PO4)2: Mn2+, Dy3+ was synthesized conventionally via homogeneous coprecipitation and conventional solid-state sintering methods. The emission peak of phosphor was found at 620 nm, which can be assigned to the 4T1g → 6A1g transition of Mn2+. The decay curves of phosphors show that Dy3+ ions co-doping can largely improve the performance of the red LLP of β-Zn3(PO4)2: Mn2+. This red long-persistent luminescence was observed for about 4 h in the limit of light perception for naked eyes when excited under 254 nm UV light for 5 min. Thermoluminescence analysis indicates that the dopant of Dy3+ ions produced suitable trap depth of defects that enhanced the luminescence of LPP. It is hypothesized that Dy3+ as a sensitizer transfers its energy to the luminescent center of Mn2+. We propose that the emission mechanism of LPP experiences a series process of electron-hole pairs: production, release, movement and combination. The decay time of LPP has close relationship with the life span of electron-hole pairs during their releasing time from traps and moving length on their path.