Wide Concentration Range of Tb3+ Doping Influence on Scintillation Properties of (Ce, Tb, Gd)3Ga2Al3O12 Crystals Grown by the Optical Floating Zone Method.

Qian Zhang,Yifei Xiong,Evgeniy Papynov,Tong Wu,Ling Wang,Oleg Shichalin,Qin Li,Yun Shi,Huan He,Jinghong Fang,Zhenzhen Zhou,Hui Wang,Xintang Huang,Qian Liu,Chaoyue Wang,Jianding Yu,Jinqi Ni

doi:10.3390/ma15062044

Abstract

To obtain a deeper understand of the energy transfer mechanism between Ce3+ and Tb3+ ions in the aluminum garnet hosts, (Ce, Tb, Gd)3Ga2Al3O12 (GGAG:Ce, Tb) single crystals grown by the optical floating zone (OFZ) method were investigated systematically in a wide range of Tb3+ doping concentration (1–66 at.%). Among those, crystal with 7 at.% Tb reached a single garnet phase while the crystals with other Tb3+ concentrations are mixed phases of garnet and perovskite. Obvious Ce and Ga loss can be observed by an energy dispersive X-ray spectroscope (EDS) technology. The absorption bands belonging to both Ce3+ and Tb3+ ions can be observed in all crystals. Photoluminescence (PL) spectra show the presence of an efficient energy transfer from the Tb3+ to Ce3+ and the gradually quenching effect with increasing of Tb3+ concentration. GGAG: 1% Ce3+, 7% Tb3+ crystal was found to possess the highest PL intensity under excitation of 450 nm. The maximum light yield (LY) reaches 18,941 pho/MeV. The improved luminescent and scintillation characteristics indicate that the cation engineering of Tb3+ can optimize the photoconversion performance of GGAG:Ce.

Highlights

The scintillator crystals with garnet structure have been proved to possess good chemical stability, high lattice isomorphic capacity and effective conversion of high energy ionizing radiation to visible luminescence when doped with luminescent rare earth ions in the host [1,2]
High pure CeO2, Gd2O3, Ga2O3, Al2O3 and Tb4O7 commercial powders (>4N) were used as starting material. They were mixed according to 6 kind of chemical stoichiometric of (Ce0.01TbxGd0.99-x)3Ga2Al3O12 (x = 1%, 7%, 15%, 33%, 50% and 66%, respectively), i.e., the seven compounds can be represented by Ce0.03Tb0.03Gd2.94Ga2Al3O12, Ce0.03Tb0.21Gd2.76Ga2Al3O12, Ce0.03Tb0.45Gd2.52Ga2Al3O12, Ce0.03Tb0.99Gd1.98Ga2Al3O12, Ce0.03Tb1.485Gd1.485Ga2Al3O12, Ce0.03Tb1.98Gd0.99Ga2Al3O12, respectively
The X-ray photoelectron spectroscopy (XPS) measurement was conducted in a XPS spectrometer (ESCALAB 250, ThermoFisher, London, UK) using the GGAG:Ce, 7% Tb and GGAG:Ce, 55% Tb crystals, high pure (>4N) commercial Tb4O7 powders were used as reference sample

Summary

Introduction

The scintillator crystals with garnet structure have been proved to possess good chemical stability, high lattice isomorphic capacity and effective conversion of high energy ionizing radiation to visible luminescence when doped with luminescent rare earth ions in the host [1,2]. Those various garnet structure compounds, when coupling with photodetectors, are widely used for applications in industry inspection, nuclear medicine, and high energy physics [3,4]. Composition engineering strategy has demonstrated its positive effects in scintillation performance improvement and the crystal structure stabilization through changing the crystal field strength and the energy level position of the luminescence activators in the bandgap [8,13–16]. The chemical composition, luminescence and scintillation properties were characterized

Crystal Growth

Characterization

Results and Discussions