Comparative study on photoluminescence of amorphous and nano-crystalline YAG: Tb phosphors prepared by a combustion method

Amorphous and nano-crystalline Y(3)Al(5)O(12):Tb phosphor samples were obtained via a facile combustion method by calcination at various temperatures, using yttrium oxide and aluminum nitrite as starting materials and citric acid as fuel. XRD. FT-IR and TEM results showed that the products were amorphous if prepared at 750 degrees C, well-crystalline when treated above 850 degrees C. In addition, partially crystalline YAG phase was observed at 800 degrees C (in air). The excitation spectra of the samples calcined at 750 degrees C and 800 degrees C exhibited some difference in the 230-255 nm range in comparison to those of nano-crystalline YAG:Tb, i.e. an extra band centered at 250 nm was detected via Gaussian curve-fitting. Furthermore, the photoluminescence intensity of assynthesized samples decreased obviously with increasing the crystallinity under 250 nm excitation. Contrary, it increased monotonously when altering the excitation wavelength to 323 nm. The concentration-dependent emission spectra of samples calcined at 800 degrees C revealed that the strongest intensity could be obtained with 10% Tb doping. Red-shifts indicated changes of the inter-atomic distances within the Tb(3+) co-ordination polyhedron with increasing Tb concentration. The low temperature photoluminescence of partially crystalline YAG:10% Tb was also investigated, displaying good-resolution but reduced intensity compared to the room-temperature photoluminescence. (C) 2011 Elsevier B.V. All rights reserved.