Valence-change- and defect-induced white luminescence of Eu2O3

Under irradiating with a CW UV laser light (gimel = 325 nm) at room temperature in vacuum and oxygen gas atmosphere, the film, microcrystals and powder compacts of Eu2O3 exhibit a reversible photoluminescence (PL) spectral change between a red sharp-line structure and a white broad one. After stopping the UV irradiation, the ability of the white PL lasts for more than several months at room temperature under room light, in spite of changes of atmosphere. The reversible phenomena to be observed are interpreted as the results of both the valence-number change of europium ions (Eu3+ --> E2+) and the oxygen vacancy formation. (C) 2001 Elsevier Science B.V. All rights reserved.