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Photostimulated Luminescence from Fluorochlorozirconate Glass-Ceramics and the Effect of Crystalline Size

Domenii publicaţii > Fizica + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: S. Schweizer, L.W. Hobbs, M. Secu, J. -M. Spaeth, A. Edgar, G. V. M. Williams and J. Hamlin

Editorial: Journal of Applied Physics, 97, p.083522, 2005.

Rezumat:

We report the results from a study of europium-doped fluorochlorozirconate glasses that have been thermally processed to induce nucleation and crystallization of BaCl2 crystallites. The resulting glass ceramics show a photostimulated luminescence (PSL) effect with a conversion efficiency
which is up to 80% of that found in the commercial crystalline x-ray storage phosphor material BaFBr:Eu2+. Thermal processing for 20 min in the range 240–260 °C produces small
(6–11 nm) hexagonal BaCl2 crystallites, while temperatures in the range 270–290 °C lead to the
formation and growth of larger s,15–100 nmd orthorhombic BaCl2 crystallites, as well as additional unidentified phases. We observe only weak PSL from glass ceramics containing
hexagonal BaCl2 s,0.1% conversion efficiency compared to BaFBr:Eu2+ at room temperatured, but orthorhombic phase crystallites give rise to a much larger relative efficiency that increases with particle size, and reaches ,80% for 100 nm diameter particles. The PSL is attributed to the
excitation of electrons trapped as F centers in the BaCl2 crystallites, while the dependence on crystallite size is consistent with a PSL-inert surface shell of thickness ,7 nm surrounding the BaCl2 crystallites.

Cuvinte cheie: glass-ceramic, luminescence,