Ce3+‐doped 20Gd2O3–20Al2O3–60SiO2 (GAS:xCe3+) glasses (x = 0.3, 0.7, 1.1, 1.5, 1.9 mol%) with Si3N4 as a reducing agent were prepared. The density of the glasses is around 4.2 g/cm3. With the increase in the Ce3+ concentration, both the photoluminescence (PL) and PL excitation peaks of GAS:xCe3+ glasses show a redshift because the 4f–5d energy levels of Ce3+ ions are narrowed. PL quantum yield and PL decay time of GAS:xCe3+ glasses are 28.32–50.59% and 43–64 ns, respectively. In addition, they both first increases and then decreases with the Ce3+ concentration increasing, reached the maximum when x = 1.1 mol%. The integrated X‐ray excited luminescence (XEL) intensity of the GAS:1.1Ce3+ glass is 23.86% of that of Bi4Ge3O12 (BGO) crystal, and the light yield reaches 1200 ph/MeV with an energy resolution of 22.98% at 662 keV when exposed to γ‐rays. The PL and XEL thermal activation energies of GAS:xCe3+ glasses are independent of Ce3+ ions concentration. Scintillating decay time of the glasses exhibits two components consisting of nanosecond and microsecond levels, and the scintillating decay time gradually decreases with the Ce3+ concentration increasing. The difference between PL and scintillating decay time is discussed regarding the different luminescent mechanisms.

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