Reversible conversion of the valence states of Eu ions in ABaPO(4) (A = Li, Na, and K) in terms of change in luminescence property

초록

We investigated the emission properties of Eu ion-doped ABaPO(4) (ABaPO(4):Eu, A = Li, Na, and K) in which the valence state of the Eu ions was controlled by annealing in various ambients, gamma-ray (gamma-ray) irradiation, and hydrogen ion (H+) implantation. We synthesized the ABaPO(4):Eu samples by solid-state reaction in air. The as-synthesized samples showed sharp red emission near 600 nm, which originated from Eu3+ ions. Interestingly, annealing under H-2 ambient changed the valence state of the Eu ions from 3+ to 2+, which was indicated by the disappearance of the red emission and concurrent emergence of strong blue emission. After subsequent annealing in O-2 atmosphere, the red emission of Eu3+ was recovered. The reversible switching between the 2+ and 3+ states was found to be repeatable by alternating H-2 and O-2 annealing. The valence state was also changed from 3+ to 2+ by H+ implantation and gamma-ray irradiation of the as-synthesized samples, possibly owing to the formation of oxygen vacancies. Our results suggest that the luminescence color of the ABaPO(4):Eu phosphors can be controlled within a range from red to blue by simple annealing in various ambients. (C) 2020 Elsevier B.V. All rights reserved.

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