PHOTOSTIMULATED LUMINESCENCE AND STRUCTURAL CHARACTERIZATION OF BA5(PO4)3CLEU2+ PHOSPHORS

Intense luminescence whose wavelength is ca. 435 nm is observed under the excitation of 680 nm in Ba5(PO4)3Cl:Eu2+ phosphors irradiated by x-rays. From ESR measurements, typical F-centers are created in the phosphors on x-ray exposure. These results clearly indicate photostimulated luminescence (PSL) occurring in these phosphors. The substitution sites of Eu2+ ions as well as the concentration of vacancies on the Cl- sites were determined by Rietveld analysis for powder x-ray diffraction patterns. The mechanism of the PSL in the phosphors is analogous to that of the PSL in the phosphor BaFCI:Eu2+ previously reported, i.e., the PSL occurs due to the liberation of electron trapped on the Cl- site vacancies (F-centers) created by the x-ray irradiation.