Abstract
In the recent successful improvement of scintillation efficiency in Lu3Al5O12:Ce driven by Ga3+ and Gd3+ admixture, the “band-gap engineering” and energy level positioning have been considered the valid strategies so far. This study revealed that this improvement was also associated with the cerium valence instability along with the changes of chemical composition. By utilizing X-ray absorption near edge spectroscopy technique, tuning the Ce3+/Ce4+ ratio by Ga3+ admixture was evidenced, while it was kept nearly stable with the Gd3+ admixture. Ce valence instability and Ce3+/Ce4+ ratio in multicomponent garnets can be driven by the energy separation between 4f ground state of Ce3+ and Fermi level.
Highlights
Scintillators are widely used in medical imaging techniques, namely, the X-ray computed tomography (CT) and positron emission tomography (PET).[1]
= Lu, Y) multicomponent garnets showed extremely high light yield up to almost 50 000 phot/MeV19,23 which is the value exceeding by 30%–40% the value of the best LYSO:Ce scintillators ever reported.[24]
According to Dorenbos,[27] the valence stability of divalent and trivalent lanthanide ions in inorganic compounds is determined by the energy difference (EFf) between the 4fn ground state of the lanthanide and the Fermi energy assumed to be located in the mid of the forbidden gap (EF)
Summary
Scintillators are widely used in medical imaging techniques, namely, the X-ray computed tomography (CT) and positron emission tomography (PET).[1]. In this Letter, X-ray excited luminescence and XANES technique were used to shed light on the relationship between luminescence and scintillation characteristics and cerium valence state in Ce-doped (Lu,Gd)3(Ga,Al)5O12:Ce multicomponent garnets.
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