We present the results of spectroscopic investigations performed on Gd-doped sol-gel silica glasses aimed at scintillator applications. Several compositions (from 0.05 to 8 mol% Gd) were studied by optical absorption (OA), radio-luminescence (RL) and time resolved photo-luminescence (PL). Moreover, the effect of a post-densification rapid thermal treatment (RTT) up to 1800°C has been studied. OA spectra showed three groups of lines characteristic of f-f transitions of Gd3+. RL spectra evidenced the Gd3+ emission at 4.01 eV due to the transition between 6P-8S states [1]. The emission line intensity was not dependent on Gd concentration. A single-exponential decay time of ?5 ms was found. After RTT, the absorption lines were low energy shifted of a few meV; the RL intensity was two orders of magnitude higher while a shorter Gd3+ emission lifetime (3 ms) was observed. Moreover, for Gd>0.5 mol%, the PL time decay curves presented an initial faster component, whose intensity increased by raising the dopant concentration. These results can be interpreted by considering Gd3+ environments modifications, leading to different probabilities of energy transfer and non-radiative recombinations [2]. In fact, TEM measurements performed on SiO2:3 mol% Gd prior to RTT showed the presence of amorphous clusters with ?10 nm diameter (Fig. 1A). After RTT, cluster diameter strongly increased up to ?50 nm (Fig. 1B). Preliminary EDS measurements indicate Gd2O3 as a possible composition for such large clusters. The vibrational absorption of Gd2O3 was monitored indeed by IR spectroscopy at ?530 cm-1. For Gd>0.5 mol%, concentrations, a new weak peak was detected at ?4250cm-1, which is suppressed by RTT. It may be attributed to the Si-OH combination mode (stretching+bending) perturbed by small Gd clusters, which can be easily dissolved by RTT at variance with the larger ones as those portrayed by TEM images. References [1]A.Vedda et al, J. Non-Cryst. Solids 345&346 338-342 (2004) [2]G. Blasse, B.C. Grabmeier, Luminescent materials, Springer Verlag (1992)
Clustering effects in Gd-doped sol-gel silica glasses
G Angella;
2005
Abstract
We present the results of spectroscopic investigations performed on Gd-doped sol-gel silica glasses aimed at scintillator applications. Several compositions (from 0.05 to 8 mol% Gd) were studied by optical absorption (OA), radio-luminescence (RL) and time resolved photo-luminescence (PL). Moreover, the effect of a post-densification rapid thermal treatment (RTT) up to 1800°C has been studied. OA spectra showed three groups of lines characteristic of f-f transitions of Gd3+. RL spectra evidenced the Gd3+ emission at 4.01 eV due to the transition between 6P-8S states [1]. The emission line intensity was not dependent on Gd concentration. A single-exponential decay time of ?5 ms was found. After RTT, the absorption lines were low energy shifted of a few meV; the RL intensity was two orders of magnitude higher while a shorter Gd3+ emission lifetime (3 ms) was observed. Moreover, for Gd>0.5 mol%, the PL time decay curves presented an initial faster component, whose intensity increased by raising the dopant concentration. These results can be interpreted by considering Gd3+ environments modifications, leading to different probabilities of energy transfer and non-radiative recombinations [2]. In fact, TEM measurements performed on SiO2:3 mol% Gd prior to RTT showed the presence of amorphous clusters with ?10 nm diameter (Fig. 1A). After RTT, cluster diameter strongly increased up to ?50 nm (Fig. 1B). Preliminary EDS measurements indicate Gd2O3 as a possible composition for such large clusters. The vibrational absorption of Gd2O3 was monitored indeed by IR spectroscopy at ?530 cm-1. For Gd>0.5 mol%, concentrations, a new weak peak was detected at ?4250cm-1, which is suppressed by RTT. It may be attributed to the Si-OH combination mode (stretching+bending) perturbed by small Gd clusters, which can be easily dissolved by RTT at variance with the larger ones as those portrayed by TEM images. References [1]A.Vedda et al, J. Non-Cryst. Solids 345&346 338-342 (2004) [2]G. Blasse, B.C. Grabmeier, Luminescent materials, Springer Verlag (1992)I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
