Changes in Luminescence of Ce:yag Crystals Under Ionizing Radiation Treatment

Abstract

Radiation induced changes in the luminescence spectrum under influence of UV light, -y-rays, electrons and protons for several concentrations of Ce3 + ions as well as Mgt+ ions in yttrium-aluminum garnet crystals were investigated. To irradiate with -y and electron as grown crystals were used while for proton irradiations the crystals were thermally annealed. For small concentrations of cerium ions (u 0.01 at.%) an increase in the luminescence (about 100%) was observed after gamma irradiation with a dose of 105 Gy. This increase was due to the growth in Ce 3 + ions concentration after γ-irradiation (= 50%), due to the Ce 4 + -> Ce3 + r e c h a r g i n g r e a c t i o n . For highly doped Ce:YAG crystals (0.1 at%, 0.2 at.%) also an increase, but much smaller (4%), for the Mg codoped crystals (0.1 at.%) was observed.After 1 MeV electron irradiation in the over-threshold type interaction a decrease in luminescence is observed due to the domination of the Ce3+ -> C e4+ ionization process. In the case of the proton irradiation, for small fluencies (Pe. 10 13 particles/cm2 ) an increase in luminescence is observed due to the domination of the recharging processes of Ce 4 + ions. For larger fluencies (> 10 14 particles/cm 2 ) a decrease takes place due to a high level of radiation defects.

Changes in Optical Properties of Ce: YAG Crystals under Annealing and Irradiation Processing

“…Fig. 1c shows results of emission measurements in the range of 450-650 nm at 5 K. Measurements performed at room temperature give the same shape of the spectrum (KACZMAREK et al 1998). Fig.…”

Persistent luminescent nanophosphors for applications in cancer theranostics, biomedical, imaging and security

“…This can be brought about by employing one of the three ways. (a) The dopant can be ionized by single-photon excitation to the 5d level, which is located inside the CB and from which the electron is finally sent to the CB The luminescence is completely quenched if all the 5d levels are inside the CB [ 79 ] (b) The RE-ion can be thermally ionized with the electron being sent to the CB if it is excited to the 5d level, just below the CB [ 80 ]. (c) Multiple-step photoionization can be employed to delocalize an electron to a trap if the 5d level is far below the CB [ 81 , 82 ].…”