Annealing Effect on Self-trapped Exciton Radiation of Nanosized Y2O3 Ceramics Radioluminescence

We measured X-ray induced luminescent radiation spectrum of nanosized Y
2
O
3
pellets sintered at 1500°C and compared the results with the samples additionally annealed for 10 h at 1000°C. Before and after additional annealing, the spectra showed changes in the wide band with a maximum at approximately 350 nm associated with self-trapped exciton relaxation. It could be explained by a modification of the electronic subsystem of the yttrium oxide, namely an increase in the phonon frequency on which the ground state energy depends. Long-term irradiation of both additionally annealed and unannealed Y
2
O
3
polycrystalline samples resulted in an exponential decrease in the intensity of the self-trapped exciton luminescence. It was caused by the fact that part of the high energy photoelectrons induced by X-ray irradiation fell into the traps of grain boundaries, where relaxation occurred through a non-radiative mechanism. Long-term irradiation increased the concentration of captured photoelectrons, but the power of the photoelectron source, which is directly responsible for the appearance of exciton d-and s-conduction electrons of yttrium and 2p-oxygen holes, decreased.