Structural and Luminescent Properties of Si4+ Co-Doped MgGa2O4:Cr3+ Near Infra-Red Long Lasting Phosphor

Abstract

In the present context, the effect of SiO2 on structural and luminescent properties in MgGa2O4: Cr3+ has been studied. The phosphors were prepared by the high temperature solid state reaction method and their structural and optical properties were studied by XRD, FESEM, FTIR, UV-Vis Diffuse Reflectance Spectroscopy, Photoluminescence Spectroscopy, Time-resolved phosphorescence emission, Decay Kinetics, Afterglow decay characterizations. Single-phased XRD patterns matching well with the standard JCPDS pattern were observed. Crystallite sizes were found to be decreased with increasing co-doping concentration of Si4+. Morphology of the samples remained invariant for Si4+ co-doping. An extra absorption band was observed at 898 cm−1 in FTIR spectra for Si4+ co-doped sample. The absorption edge position in diffuse reflectance spectra was found to be red shifted when Si4+ was co-doped. The bandgap values slightly decreased with increasing co-doping concentration of Si4+. Photoluminescence emission originated from Cr3+ emitting centers peaking at 708 nm corresponding to 2E(2G) → 4A2(4F) transition and photoluminescence emission intensity was found to be increased in Si4+ co-doped sample. The phosphor with 2 mol% Si4+ co-doping showed highest photoluminescence intensity and highest average lifetime. Afterglow decay measurements reveal that the phosphors can glow for more than 3600 s. A possible mechanism for long persistent luminescence phenomenon has been discussed.