Evidences of Rare Earth Ion Aggregates in a Sol−Gel Silica Matrix:  The Case of Cerium and Gadolinium

Abstract

Structural and morphological studies were carried out on cerium-and gadolinium-doped sol-gel silica glasses intended for scintillator applications, to deepen the understanding of rare earth ion incorporation into the glass matrix. Several compositions, ranging from 0 to 5 mol % Ce and from 0 to 8 mol % Gd, were studied by Raman spectroscopy. The vibrational response was compared to that of pure silica glasses: for cerium doping higher than 0.5 mol %, the F 2g Raman mode, characteristic of CeO 2 , was observed. The presence of CeO 2 nanocrystalline clusters, whose size depends on cerium concentration and thermal treatment, was confirmed also by X-ray powder diffraction (XRD) patterns and transmission electron microscopy (TEM) analyses. On the contrary, gadolinium-doped sol-gel silica glasses exhibited Raman spectra similar to those of pure silica glasses, at least for the investigated concentrations up to 8 mol %, and no crystalline particles were detected within the amorphous matrix.

Gd-incorporation and luminescence properties in sol–gel silica glasses

“…In view of utilization of RE-doped silica as scintillating material, previous researches by our group were devoted to luminescence studies of Ce-, Gd-, Tb-and Yb-doped sol-gel silica glasses [12][13][14][15][16][17][18]. Ce-doped sol-gel silica glasses exhibited excellent scintillation properties [12][13][14][15][16][17] and were also successfully tested in fiber form as real time remote radiation dosimeters [19,20].…”

“…Ce-doped sol-gel silica glasses exhibited excellent scintillation properties [12][13][14][15][16][17] and were also successfully tested in fiber form as real time remote radiation dosimeters [19,20]. At Ce concentrations higher than 1 mol%, the formation of crystalline CeO 2 aggregates was noticed [14], and the influence of Ce aggregation phenomena on Ce 3+ optical properties was also investigated [17].…”

Ce-doped SiO 2 optical fibers for remote radiation sensing and measurement

“…Variables in this first phase consisted in doping with different rare earth ions (cerium, europium, gadolinium, terbium, ytterbium) and in variation of sintering conditions for Ce doped sol-gel matrices (either oxidizing or reducing atmosphere ) [22][23][24][25][26][27]. Following these previous tests, further investigation was restricted to Cerium and Europium doping.…”

“…In this paper, we propose a novel type of glass composite fiber dosimeter based on the RL emission of a small portion of glass fiber doped with Cerium. Previous investigations already demonstrated the interesting RL properties of these composite fibers [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. Moreover, with the aim to better separate the Cherenkov emission from the scintillating signal [36,37] an alternative Eu doped fiber was produced, tested and compared with Ce-doped ones.…”

Infrared luminescence for real time ionizing radiation detection

“…[4][5][6] Such Ce-doped fibers were successfully applied for monitoring low energy diagnostic beams and small radiation fields. 7,8 However, the measurements are problematic in the case of extended radiation fields and for beam energies above the Cerenkov threshold (approximately 190 keV for silica) like those employed in medical radiation therapy.…”