Effect of Mg substitution in Sr2SiO4:Eu2+ nanophosphors for blue and white emission at near UV excitation
Nanophosphors of (Sr0.98-xMgxEu0.02)2SiO4 (x=0, 0.18, 0.38, 0.58 and 0.78) were prepared through low temperature solution combustion method and their luminescence properties were studied. The emission peak for Eu2+ doped Sr2SiO4 nanophosphor is observed at ~490 nm and ~553 nm corresponding to two Sr2+ sites Sr(I) and Sr(II) respectively for 395 nm excitation but the addition of Mg2+ dopant in Sr2SiO4 leads to suppression of ~553 nm emission peak due to absence of energy levels of Sr (II) sites which results in a single broad emission at ~460nm. It was shown that the emission peak blue shifted with increase in Mg concentration which may be attributed to change in crystal field environment around Sr(I) sites. Therefore the (Mg0.78Sr0.20Eu0.02)2SiO4: Eu2+ nanophosphor can be used for blue emission and the Sr2SiO4:Eu0.042+ for green-yellow emission at 395 nm excitations. The CIE coordinates for mixed powders of (Mg0.78Sr0.20Eu0.02)2SiO4 and Sr2SiO4:Eu0.042+ (in 1: 1 ratio) falls in the white region demonstrating the possible use of the mixture in white light generation using near UV excitation source.