EPR and luminescence properties of combustion synthesized LiAl5O8:Mn phosphors

LiAl5O8:Mn2+ phosphors have been synthesized by combustion process in a short time (<5 min). X-ray diffractogram confirms that the synthesized material consists of LiAl5O8 as main phase. Scanning electron microscopy showed angular plate-like crystals with non-uniform shape. The EPR spectra of Mn2+ ions exhibit resonance signals at g ≈ 4.28 and g ≈ 2.0. The signal at g ≈ 2.0 is due to Mn2+ ions in an environment close to tetrahedral symmetry, whereas the resonance at g ≈ 4.28 is attributed to the rhombic surroundings of the Mn2+ ions. The variation of zero-field splitting parameter (D) with temperature is measured and discussed. The PL spectra exhibit green emission peaks at 505 and 518 nm which are due to the 4T1 (G) → 6A1 (S) transition of Mn2+ ions. The EPR study of LiAl5O8:Mn2+ phosphor gives clear indication of the Mn2+ ions occupying more than one site in this phosphor.