EPR, luminescence and IR studies of Mn activated ZnGa2O4 phosphor

Electron paramagnetic resonance (EPR), luminescence and infrared spectra of Mn2+ ions doped in zinc gallate (ZnGa2O4) Powder phosphor have been studied. The EPR spectra have been recorded for zinc gallate phosphor doped with different concentrations of Mn2+ ions. The EPR spectra exhibit characteristic spectrum of Mn2+ ions (S = I = 5/2) with a sextet hyperfine pattern, centered at g(eff) = 2.00. At higher concentrations of Mn2+ ions, the intensity of the resonance signals decreases. The number of spins participating in the resonance has been measured as a function of temperature and the activation energy (E-a) is calculated. The EPR spectra of ZnGa2O4: Mn2+ have been recorded at various temperatures. From the EPR data, the paramagnetic susceptibility (X) at various temperatures, the Curie constant (C) and the Curie temperature (theta) have been evaluated. The emission spectrum of ZnGa2O4: Mn2+ (0.08 mol%) exhibits two bands centered at 468 and 502 nm. The band observed at 502 nm is attributed to T-4(1) --> (6)A(1) transition of Mn2+ ions. The band observed at 468 DID is attributed to the trap-state transitions. The excitation spectrum exhibits two bands centered at 228 and 280 nm. The strong band at 228 nm is attributed to host-lattice absorption and the weak band at 280 nm is attributed to the charge-transfer absorption or d(5) --> d(4)s transition band. The observed bands in the FT-IR spectrum are assigned to the stretching vibrations of M-O groups at octahedral and tetrahedral sites. (C) 2004 Elsevier Ltd. All rights reserved.