Scintillation properties of Ce3+ doped SiO2-Al2O3-Gd2O3 glass

Scintillation glass is an attractive material due to its many advantages including low-cost and easy-manufacturing compared with single crystal. However the low density of glass scintillator restricts its applications. The introduction of heavy components such as PbO and Bi2O3 allows the density of the glass to be easily increased to more than 6.0 g/cm3 which is desirable for most applications. However, it is usually accompanied with a dramatic decrease in the luminescence response of Ce3+ ions. Although Gd2O3 based glass has a relatively high light yield, it is far below the high silica glass. In order to explain why the luminescent efficiency of Ce3+ doped glass with low density is high while that with high density is low, a glass-forming region of SiO2-Al2O3-Gd2O3 ternary system is achieved by high-temperature melt-quenching method. Ce3+doped SiO2-Al2O3-Gd2O3 and SiO2-Al2O3-Gd2O3-Ln2O3 (Ln=Y, La, Lu) scintillation glasses are prepared at reducing atmosphere. Their optical and scintillation properties are investigated. The results show that the content of Gd2O3 can reach as high as 30% mol without phase separation. In addition, the UV cut-off position is red-shifted, PL intensity decreases and decay time reduces from 70 to 37.6 ns with increasing the Gd2O3 concentration. After Lu2O3, La2O3, Y2O3 are added in the glass, the UV cut-off position is red-shifted and PL intensity decreases. Moreover the UV cut-off position is in the order of La>Y>Lu and the decay time is in the order of La2O3 is more than 10% mol, X-ray excited luminescence light emission intensity reduces from 61% of BGO to 13% of BGO. With the UV cut-off position red-shifted, the bandgap of glass becomes narrow, resulting in the 5 d level of Ce3+ ions gradually approaching to the conduction band and the 5 d electrons easily combining with the holes in the glass through the conduction band. Namely, charge transferring quenching occurs. This is the reason why the PL intensity and decay time both decrease. It can also explain why the luminescent efficiency of Ce3+ doped glass with low density is high while that with high density is low.