Preparation of Glass-Ceramic Materials by Controlled Crystallization of Eu(2)O(3)-Doped WO(3)-B(2)O(3)-La(2)O(3) Glasses and Their Luminescent Properties.

In this paper, the crystallization behavior of 52WO(3):22B(2)O(3):26La(2)O(3):0.5Eu(2)O(3) glass has been investigated in detail by XRD and TEM analysis. The luminescent properties of the resulting glass-ceramics were also investigated. By XRD and TEM analysis, crystallization of β-La(2)W(2)O(9) and La(2)WO(6) crystalline phases has been proved. Photoluminescent spectra showed increased emission in the resulting glass-ceramic samples compared to the parent glass sample due to higher asymmetry of Eu(3+) ions in the obtained crystalline phases, where the active Eu(3+) ions are incorporated. Also, in the glass-ceramics, the crystalline particles are embedded in the amorphous matrix and more of them are separated from each other which improves the light scattering intensity from the free interfaces of the nanocrystallites, resulting in the enhancement of the PL intensity. It was established that the optimum emission intensity is registered for glass-ceramic samples obtained after an 18 h heat treatment of the parent glass. After 21 h of glass crystallization, the amount of crystallite particles is high enough, and they are in close proximity to each other, and hence, the average distance between europium ions decreases, resulting in quenching of Eu(3+) and a decrease in the emission intensity. Additionally, at 21 h of glass crystallization, formation of new crystalline phase-La(2)WO(6) is established. A redistribution of Eu(3+) ions in the different crystalline compounds is most likely taking place, which is also not favorable for the emission intensity.