Stable Ce4+ centres - a tool to optimize cathodoluminescence performance in garnet scintillators

Garnet single crystals are widely used as scintillators in electron detectors. Cerium activated lutetium aluminum garnet Cex:Lu3-xAl5O12 (LuAG:Ce) is a promising example of such material for these applications. This is mainly due to its high light yield (LY) of 25 kph/MeV, short decay time of 60–80 ns, high atomic density (6.7 g/cm3), and high radiation stability with no hygroscopicity. The cathodoluminescence (CL) performance can be improved by Ga and Gd doping the garnet matrix. Proper admixture of these elements can increase the LY to 50–60 kph/MeV in addition to eliminating unwanted slower decay components. There was an idea that further decay acceleration can be achieved by doping the garnet with monovalent (Li+) or divalent ions (Mg2+, Ca2+). This should increase the valency of some Ce3+ centres to Ce4+ which should better compete with electron traps, and thus accelerate the decay. Our previous work proved the same decay trend, however, at a price of the LY. Such LY loss may induce the idea, if the stable Ce4+ centres are really participating in Ce3+ emission