Luminescence and EPR studies of Mn-activated SrAl12O19 phosphor prepared by facile combustion approach

Manganese-activated strontium hexa-aluminate (SrAl12O19) phosphor has been prepared at low temperature (500 °C) and in a very short time (<5 min) by urea combustion route. Powder X-ray diffraction pattern showed the presence of hexagonal SrAl12O19 phase. Scanning electron microscopy (SEM) indicated the presence of several particles with sizes of 200 nm. The luminescence of Mn2+ activated SrAl12O19 exhibits a strong green emission peak around 515 nm from the synthesized phosphor particles under excitation (451 nm). The luminescence is assigned to a transition from the upper 4T1→6A1 ground state of Mn2+ ions. EPR investigations also indicated the presence of Mn2+ ions in the prepared material. From the observed EPR spectrum, the spin-Hamiltonian parameters have been evaluated. The magnitude of the hyperfine splitting (A) constant indicates that there exists a moderately covalent bonding between Mn2+ ions and the surrounding ligands. The variation of zero-field splitting parameter (D) with temperature is measured and discussed. The mechanism involved in the generation of a green emission has been explained in detail.