Evaluation of properties of YAG (Ce) ceramic scintillators

We measured basic properties of three ceramic Y₃Al₅O₁₂ (YAG) scintillators doped with Ce to a concentration of 0.5, 0.05, and 0.005 mol%, in comparison with a monocrystalline YAG scintillator with unknown amount of Ce doping. First, optical transparency and emission spectra were investigated. We confirmed that the transparency of the ceramics is comparable to that of the monocrystalline one (∼80%) in wavelengths longer than ∼500 nm. The ceramics did not show an indication of lattice defects which is present in the monocrystalline YAG. Then the response to γ-rays was studied using a phototube as a scintillation light detector. The 0.5 mol% sample exhibited the highest light yield (∼40% of CsI), with an energy resolution of about 7.2% at ¹³⁷Cs 662 keV photoabsorption peak. The optimum Ce concentration for a ∼2 mm thick ceramic YAG was determined to be ∼0.1 mol%. Using the delayed coincidence method, the principal time constant of the ceramic YAGs was measured as ∼80 ns. By irradiating 5.49 MeV α-particles, the α-ray to γ-ray light yield ratio of the ceramic YAGs was found to depend negatively on the amount of Ce; namely, 0.28, 0.20, and 0.13 in the increasing order of the Ce concentration. The 200-1000 keV intrinsic background of the 0.5 mol% ceramic was ∼10^-5 counts/s/cm³, indicating that it is not significantly contaminated by radioactive impurities.