Endowing Cr3+-doped non-gallate garnet phosphors with near-infrared long-persistent luminescence in weak fields

Recently, Cr3+-doped gallates near-infrared (NIR) long persistent phosphors (LPPs) have been developed. However, Cr3+-doped non-gallate NIR LPPs is little. Herein, we propose two alternative hosts (Na2CaSn2Ge3O12 and Na2CaTi2Ge3O12) for Cr3+-doped non-gallate garnet NIR LPPs. These phosphors were fabricated by a conventional solid-state method in air atmosphere. Predominant cubic phase of these phosphors were observed in XRD patterns. Cr3+ ions locate at weak field in the two hosts and emit a broadband emission due to 4T2→4A2 transition which were illustrated by Tanabe-Sugano matrix and spectroscopic data, respectively. Systematic investigations of the nature of energy traps were carried out by thermoluminescence measurement. Finally, the long persistent luminescence mechanism is also reported in this study.