Rare-earth doped sol-gel silicate glasses for scintillator applications

Radio-, photo- and thermally stimulated - luminescence (RL, PL, TSL) measurements have been performed on SiO2 sol-gel glasses doped by 0.1 mol% Ce and 3 mol% Gd, and on (0.1 mol% Ce, 3 mol% Gd) co-doped samples. Ce3+ 5d-4f emission F caking at about 2.7 eV has been observed in the RL of SiO2: 0.1 mol% CC, while the typical (6)p-S-8 emission of Gd3+ centred at 3.97 eV has been detected in SiO2: 3 mol% Gd. The co-doped sample displays both 5d-4f Ce3+ and P-6-S-8 Gd3+ emissions with reduced intensities with respect to those observed in the singly doped glasses. Moreover, in co-doped glasses the PL time decay patterns of both rare earth ions show a non exponential dependence and are significantly shortened. To explain such an effect non radiative de-excitation of both RE ions excited states involving energy transfers to defect levels is suggested. Bidirectional Gd3+ <-> Ce3+ energy transfers could also occur. Complementary TSL measurements put in evidence the existence of broad glow peaks at about 100 K and 220 K. The TSL spectra feature the RE ions emissions.