Rare earth activated yttrium aluminate phosphors with modulated luminescence.

Yttrium aluminate (Y(3)A(5)O(12)) was doped with different rare earth ions (i.e. Gd3+, Ce3+, Eu3+ and/or Tb3+) in order to obtain phosphors (YAG:RE) with general formula,Y3-x-aGdxREaAl5O12 (x = 0; 1.485; 2.97 and a = 0.03). The synthesis of the phosphor samples was done using the simultaneous addition of reagents technique. This study reveals new aspects regarding the influence of different activator ions on the morpho-structural and luminescent characteristics of garnet type phosphor. All YAG:RE phosphors are well crystallized powders containing a cubic-Y3Al5O12 phase as major component along with monoclinic-Y4Al2O9 and orthorhombic-YAlO3 phases as the impurity. The crystallites dimensions of YAG:RE phosphors vary between 38 nm and 88 nm, while the unit cell slowly increase as the ionic radius of the activator increases. Under UV excitation, YAG:Ce exhibits yellow emission due to electron transition in Ce3+ from the 5d level to the ground state levels (F-2(5/2), F-2(7/2)). The emission intensity of Ce3+ is enhanced in the presence of the Tb3+ ions and is decreased in the presence of Eu3+ ions due to some radiative or non-radiative processes that take place between activator ions. By varying the rare earth ions, the emission colour can be modulated from green to white and red. Copyright (c) 2015 John Wiley & Sons, Ltd.