Abstract
Different Eu2O3 fine particle films were prepared by the laser ablation method. Under a continuous wave (CW) 325 nm laser light irradiation, their photoluminescence spectra are measured both in vacuum and in O2 gas atmosphere. All the specimens display reversible spectral change and clear luminescence colour changes (red luminescence ↔ white luminescence) for changing specimen atmosphere. Moreover, the white-luminescent state is stored for more than several years at room temperature in air under room light. The obtained results suggest that the spectral changes arise from both the photo-induced valence (Eu3+ → Eu2+) change of europium ions and the photo-generated oxygen defect structure at Eu2O3 particle surfaces in vacuum, which is expressed by the following reaction, Eu2O3 in lattice + CW 325 nm photon → (Eu2+-oyygen vacancy-Eu2+) complex +½O2. The obtained results are discussed in the light of the exciton theory.
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