Emission and EPR studies on green and red color emitting gallate phosphor containing manganese/chromium ions

Abstract

The ZnGa2O4:Mn2+/Cr3+ ceramic phosphor is synthesized via high temperature solid state reaction method and then phosphor is intensively studied for green/red color emission. Prepared samples are structurally characterized through powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) and it is found that the samples possess single phase cubic spinel structure. The X-ray photoelectron spectroscopy (XPS) is performed for the identification of chemical states of different elements present in the samples. The Zn0.9Ga2O4:0.1%Mn2+ sample has shown broad emission band (475–575 nm) having peak at 505 nm (green) due to the electronic transition of Mn2+ ion. The ZnGa1.9O4:0.1%Cr3+ sample has shown intense emission at 696 nm (deep red) due to the 2E (2G) →4A2(4F) transition of Cr3+ ions. The co-doped Zn0.9Ga1.9O4:Mn2+/Cr3+ sample on the other hand can be excited with different excitations to give green and red emissions. Electron paramagnetic resonance (EPR) spectroscopy is done to inspect defects caused by the substitution of Ga3+ and Zn2+ by Cr3+ and Mn2+ ions, respectively. Emission decay measurements are done to decipher afterglow and photoluminescence decay.