On the recombination mechanism in x-ray storage phosphors based on lanthanum fluoride

• Published in: Journal of luminescence 1994, Vol.59 (6), p.377-383
• Main Authors: Schipper, W.J., Blasse, G.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other luminescence and radiative recombination; Other solid inorganic materials; Photoluminescence; Physics; Thermoluminescence
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/0022-2313(94)90065-5

LaF 3 doped with trivalent rare earths can act as an X-ray storage phosphor. Trivalent luminescent rare earth ions are used as a probe to elucidate the recombination mechanism. The photoluminescence emission spectra of LaF 3:RE 3+ (RE = Ce, Pr, Gd, Tb, Dy, Ho, Tm) are compared to those of the thermally stimulated luminescence (TSL) after X-ray irradiation. In the TSL spectra of LaF 3: Pr 3+, LaF 3: Tb 3+, LaF 3: Ho 3+ and LaF 3: Tm 3+ the emissions from the higher excited states are weaker or absent. LaF 3: Ce 3+ and LaF 3: Gd 3+ do not exhibit thermally stimulated emission. It is proposed that upon recombination an exciton is formed, which is able to transfer its energy to Pr 3+, Tb 3+, Dy 3+, Ho 3+ and Tm 3+ at about 22000 cm -1. The lowest excited levels of Ce 3+ and Gd 3+ in this lattice are at too high energy to allow this transfer.