Aluminum effect on photoluminescence properties of sol-gel-derived Eu3+-activated silicate glasses

Eu2O3-Al2O3-SiO2 monolithic xerogels doped with 2000 ppm Eu/Si and 5000 ppm Eu/Si, were prepared with different Al/Eu molar ratios: (a) 0, (b) 0.25, (c) 0.5, (d) 0.75, (e) 1, (f) 3, (g) 6, (h) 10, and (i) 15. The samples were investigated by photoluminescence spectroscopy. When we compare the spectra of the Al3+ -co-doped xerogels with those of the samples without aluminum, several significant differences of the spectroscopic features appear: (i) the D-5(0) -> F-7(0) transition exhibits a blue shift; (ii) the emission bands broaden; (iii) the relative amplitude among the different transitions changes as well as (iv) the splittings of the Stark components of the D-5(0) -> F-7(J) transitions, and (v) the D-5(0) level decay curves present a stretched exponential like profile. The results are discussed with the aim of assessing the effect of the AI/Eu molar ratio on the structural and spectroscopic properties of Eu2O3-Al2O3-SiO2 xerogels.