Synthesis and luminescence properties of a broadband near-infrared emitting non-gallate persistent luminescence Mg1.4Zn0.6SnO4:Cr3+ phosphor†
A series of novel non-gallate near-infrared long-persistent phosphorescence Mg2−xZnxSnO4:Cr3+ phosphors were synthesized, and their structure and luminescence properties were investigated systematically. Under 448 nm blue light excitation, all the phosphors exhibit a broad emission band centered at 730 nm and a shoulder peak at 708 nm, which are attributed to the 4T2(4F) → 4A2 and 2E → 4A2 transitions of Cr3+, respectively. The excitation spectra of the samples clearly show the characteristic excitation of Cr3+ in the octahedral crystal field, with three obvious peaks at 324, 448 and 620 nm respectively. The phosphor with a composition of Mg1.4Zn0.6SnO4:0.03Cr3+ shows the strongest photoluminescence intensity which is 2.87 times and 3.09 times that of Mg2SnO4:0.03Cr3+ and Zn2SnO4:0.03Cr3+, respectively. Besides, all the samples show intense near-infrared long-persistent phosphorescence. For the optimized sample Mg1.4Zn0.6SnO4:0.005Cr3+, its phosphorescence can still be observed with a night vision instrument 18 h after removing the 365 nm UV light source. Finally, a feasible phosphorescence mechanism of the Mg1.4Zn0.6SnO4:Cr3+ phosphor was proposed and discussed. This study may provide a new method for developing novel near-infrared long-persistent phosphorescence phosphors through crystal structure modification.