Roles of Nd3+ in enhancing Mn2+-Activated SrZn2(PO4)2 long persistent phosphor

SrZn 2 (PO 4 ) 2 : Mn 2+ , Nd 3+ materials were synthesized using a solid-state reaction method. The prepared materials display long afterglow properties with a broadband yellowish-green emission at Peak 550 nm attributed to the 4 T 1 ( 4 G) → 6 A 1 ( 6 S) transition of the Mn 2+ ion as a luminescent center. The sensitizing ion Nd 3+ also contributes the green emission at the peak of 518 nm attributed to its 4 G 7/2 → 4 I 9/2 transition. The luminescent and structural properties of the materials were studied by XRD, SEM-EDS, XPS, excitation and emission spectra, decay curves and thermoluminescence (TL) and EPR analysis. The non-equivalent substitution of Nd 3+ for Sr 2+ results in N d S r • defects, which significantly increases the effective trap concentration of the materials. The fluorescence spectra show that there is a band overlap between the excitation spectrum of SrZn 2 (PO 4 ) 2 : Mn 2+ and the emission spectrum of SrZn 2 (PO 4 ) 2 : Nd 3+ , illustrating a phenomenon of Nd 3+ → Mn 2+ energy transfer. The luminescent mechanism of the materials is explored. • The reported SrZn 2 (PO 4 ) 2 : Mn 2+ , Nd 3+ phosphors exhibit obvious yellow-green long afterglow phosphorescence. • The properties and attributions of defects in phosphors were studied using compound determination techniques. • Based on energy band theory and defect theory, the luminescence mechanism of Mn 2+ , Nd 3+ co-doped SrZn 2 (PO 4 ) 2 phosphors was established. • In SrZn 2 (PO 4 ) 2 : Mn 2+ , Nd 3+ , Nd 3+ ions not only act as a sensitizer ion to transfer energy but also acts as a defect provider to increase the effective defect concentration of the material, enhancing the luminescence intensity and extending the afterglow time of SrZn 2 (PO 4 ) 2 : Mn 2+ , Nd 3+ phosphors.