Photoluminescence and photostimulated luminescence of BaFBr:Eu2+,Eu3+

In the photoluminescence (PL) of BaFBr:Eu2+,Eu3+, the emissions of Ea(2+), carrier electron-hole (e-h) recombination, and Eu3+ are observed, while in the photostimulated luminescence (PSL) only the emission of Eu2+ is exhibited. This disappearance of e-h recombination in PSL is considered to be caused by carrier migration during photo-stimulation. (C) 1997 American Institute of Physics.

Photostimulated luminescence of BaFBr:Eu2+ phosphors

After x-irradiation for 10 s, luminescence from BaFBr:Eu2+ phosphors by photostimulation of longer wavelength than F absorption bands was observed and assigned to the surface states or intrinsic defects of the powders. It is found that the luminescence by photostimulation into F bands can be reduced via electron migration from F centers into the surface states or intrinsic defects, thus reducing the x-ray storage or image stability. Surface passivation can lower these defects and improve the phosphors or imaging plate quality. (C) 1996 American Institute of Physics.

PROCESS OF PHOTOLUMINESCENCE AND PHOTOSTIMULATED LUMINESCENCE IN BAFBR-EU PHOSPHORS

The photoluminescence (PL) and photostimulated luminescence (PSL) of BaFBr: Eu phosphors are reported. In the photoluminescence of BaFBr:Eu, the emission of Eu2+, e-h recombination and Eu3+ have been observed, while in the photostimulated luminescence only the emission of Eu2+ was observed. This phenomenon may be explained well by the suggestion of a two-hand model for the host emission in which the host emission energy may transfer to Eu2+ difference of excitation in those two processes results in different transfer rates which makes the PL and PSL emission different.

New color centers and photostimulated luminescence of BaFCl : Eu2+

Three new absorption bands, appearing around 670, 865 and 980 nm, are observed in BaFCl:Eu2+ phosphors. They are ascribed to F aggregates formed by association of F centers or by trapping of electrons to the primary F-n(+) (n = 2,3,4) centers. The growth curves of F and F-aggregated centers are similar and may be divided into three stages. The photostimulated luminescence (PSL) decays by stimulation into the absorption bands of F centers and of F aggregates are different; the former decay logarithmically and the latter decay hyperbolically. Some non-radiative processes related to F aggregates, such as electron migration, occur accompanying the PSL process, which may reduce the PSL efficiency and sensitivity of the phosphors. (C) 1997 Published by Elsevier Science Ltd. All rights reserved.

Electron migration in BaFCl:Eu2+ phosphors

Here we report the electron migration by photo- or thermostimulation in BaFCl:Eu2+. Electrons released from F centers may be trapped by other defect sites to form F aggregates or another type of F center and vice versa. This migration reduces the photostimulated luminescence efficiency, lowers the imaging plate sensitivity, and causes the difference between the optical absorption and photostimulation spectra of color centers. (C) 1997 American Institute of Physics.