Composition–property relationships in (Gd3−xLux)(GayAl5−y)O12:Ce (x = 0, 1, 2, 3 and y = 0, 1, 2, 3, 4) multicomponent garnet scintillators

• The influence of Gd3+–Ga3+ admixture on the luminescent mechanism was studied.
• The promising composition for scintillation application was achieved.
• Energy transfer from Gd3+ to Ce3+ was corroborated.
• Band gap engineering and energy level positioning strategies were discussed.
• The luminescence behaviors varying with electronic structures were demonstrated.

The (LuxGd3−x)(GayAl5−y)O12:Ce (x = 0, 1, 2, 3 and y = 0, 1, 2, 3, 4) scintillating polycrystalline powders were prepared by high temperature solid state reaction method. A pure cubic phase was confirmed in all samples by X-ray diffraction (XRD). X-ray excited luminescence (XEL), photoluminescence excitation and emission spectra were employed to study the influence of Gd3+–Ga3+ admixture on the luminescent mechanism of Ce3+ as well as the energy transfer from Gd3+ to Ce3+. The band-gap structures with varying Gd3+ and Ga3+ content were constructed to understand the luminescence behaviors. In addition, thermoluminescence spectra (TL) were utilized to identify the moving of conduction band (CB) by monitoring the shift of the corresponding TL peaks. Finally, it was found that incorporation of 40 mol% (y = 2) Ga3+ and 33.3–66.7 mol% (x = 1–2) Gd3+ could secure enough energy-separation between CB and 5d1 of Ce3+ avoiding thermal ionization effect at utmost, and bury the antisite defect traps into CB, and in turn achieving the optimum scintillation efficiency.