Characterization, EPR and luminescence studies of ZnAl2O4:Mn phosphors

ZnAl2O4:Mn green light emitting powder phosphors have been prepared by urea combustion technique involving furnace temperatures about 500 °C in a short time (<5 min). The prepared powders were characterized by X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectrometry and the surface area measurements by a Brunauer-Emmet-Teller (BET) adsorption isotherms. The EPR spectrum exhibits a resonance signal at g≈2.0, which shows a six-line hyperfine structure (hfs). From the EPR spectra the spin-Hamiltonian parameters have been evaluated at room temperature as well as at 110 K. EPR and photoluminescence (PL) studies revealed that manganese ions were present in divalent state and the site symmetry around Mn2+ ions is distorted tetrahedral. The spin concentration (N), the paramagnetic susceptibility (χ) and the zero-field splitting parameter (D) have been evaluated and discussed. The green emission at 511 nm in ZnAl2O4:Mn phosphor is assigned to a transition from the upper 4T1→6A1 ground state of Mn2+ ions.