Preparation of Glass-Ceramic Materials by Controlled Crystallization of Eu2O3-Doped WO3-B2O3-La2O3 Glasses and Their Luminescent Properties

In this paper, the crystallization behavior of 52WO3:22B2O3:26La2O3:0.5Eu2O3 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 beta-La2W2O9 and La2WO6 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 Eu3+ ions in the obtained crystalline phases, where the active Eu3+ 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 Eu3+ and a decrease in the emission intensity. Additionally, at 21 h of glass crystallization, formation of new crystalline phase-La2WO6 is established. A redistribution of Eu3+ ions in the different crystalline compounds is most likely taking place, which is also not favorable for the emission intensity.