Single crystal scintillators based on the cerium-doped (Gd,Lu,Y)3(Al,Ga)5O12 garnet host were first reported in 2011 [1,2]. Balanced content of Gd and Ga resulted in enormous increase of light yield of nearly 300% compared to high density Lu3Al5O12:Ce garnet. Qualitative explanation of such an increased performance was provided based on the inactivation of shallow electron traps due to the decrease of the bottom edge of conduction band and at the same time keeping sufficient ionization barrier of 5d1 excited state of Ce3+ to prevent ionization losses of emission center around room temperature.
In 2014 another optimization tool was reported, namely the divalent cooping of such garnets [3,4] which stabilizes part of cerium ions in 4+ charge state. The Ce4+ center in garnet lattice provided another fast radiative recombination pathway in scintillation mechanism which noticeably improved especially timing characteristics of these scintillators.
These findings immediately made these materials highly competitive in practical applications. Up to three inch diameter single crystals can be manufactured, and there are already several companies which sell so called GAGG:Ce (Gd3(Ga,Al)5O12:Ce) scintillator.
Given the multicomponent nature of such garnet scintillators, the physical mechanism of scintillation appears complicated and energy transfer and trapping processes in it as well.
This talk will review 10 year’s history of R&D of these materials and current status of understanding their scintillation mechanism with prospectives for further development and optimization.
1. K. Kamada et al, Crystal Growth & Design 11, 4484-4490 (2011).
2. K. kamada et al, J. Phys. D: Appl. Phys. 44 (2011) 505104
3. M. Nikl et al, Crystal Growth Design 14 (2014) 4827
4. K. Kamada et al, Optical Materials 41 (2015) 63