Persistent luminescence of RE3+ co-doped Sr3B2O6:Eu2+ yellow phosphors (RE = Nd, Gd, Dy)
Abstract
Bright and persistent luminescence in the yellow to reddish region was observed in newly developed Sr3‑x-yB2O6:xEu2+,yRE3+ (RE = Nd, Gd, Dy) phosphors. The effects of a series of RE3+ co-dopants (RE = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, or Yb) on achieving persistent luminescence were evaluated by varying the reducing conditions and laser illumination time. The Eu2+ single-doped and Eu2+/Dy3+ co-doped samples showed a large red-shift in phosphorescence emission. The persistent luminescence intensity increased with increasing illumination time of a 355nm laser, which is unique to these persistent phosphors. The PL decay rates were well fitted to either the bi- or tri-exponential forms. The PL decay modes were discussed in relation to the ionization potential of RE3+ ions and oxygen vacancies. The covalent characters of the B-O and Sr-O bonds for both the reduced and oxidized samples were calculated and compared with the electron density distribution map obtained using the maximum entropy method. The electron density contours around the O2- apices of the BO3 triangle was relaxed outwardly in the reduced sample. This relaxation could reinforce the nephaulexetic effect in Sr (Eu2+)-O coordination.
- Publication:
-
Journal of Luminescence
- Pub Date:
- February 2018
- DOI:
- 10.1016/j.jlumin.2017.09.031
- Bibcode:
- 2018JLum..194..649C
- Keywords:
-
- Persistent luminescence;
- Red shift;
- Strontium borate;
- RE<SUP loc="post">3+</SUP> co-doped;
- Yellow-reddish;
- Covalency;
- Electron density distribution