Reversible photoinduced spectral transition in Eu_2O_(3-γ)Al_2O_3 composites at room temperature

摘要

The photoluminescence (PL) intensity of Eu_2O_(3-γ)Al_2O_3 composite has been found to decrease at room temperature with 325 nm laser light irradiation in vacuum, without any accompanying white luminescence. Then, under the same laser light irradiation in oxygen gas atmosphere, the PL intensity recovers. Through many successive experiments, it is found that the spectral change is nearly reversible. In spite of the changing atmosphere (for example, oxygen gas and air exposures), each PL state is stored for a long time at room temperature after the removal of the laser light under room light. This phenomenon is interpreted as results of photoinduced valence-number change of europium ions, the oxygen vacancy formation and some excitation energy transfer. Such a reversible phenomenon may well yield materials for erasable optical storage and oxygen sensor.