Wavelength dependent loading of traps in the persistent phosphor SrAl2O4:Eu2+, Dy3+

Abstract

The persistent phosphorescence and thermoluminescence of SrAl 2 O 4 :Eu 2+ :Dy 3+ is reported for a variety of different excitation wavelengths and excitation temperatures, to provide new insights in the mechanism of the trapping and detrapping. These measurements reveal that the trapping is strongly dependent on the wavelength and temperature. First, with increasing loading temperature, the thermoluminescence peak shifts to lower temperatures which corresponds to a change of trap population. Secondly, the integrated thermoluminescent intensity increases with increasing loading temperature. All wavelength and temperature dependent experiments indicate that the loading of the traps is a thermally activated processes. Utilizing different wavelengths for loading, this effect can be enhanced or reduced. Furthermore excitation with UV-B-light reveals a tendency for detrapping the phosphor, reducing the resulting thermoluminescent intensity and changing the population of the traps.

Thermal and concentration dependent energy transfer of Eu^2+ in SrAl_2O_4

“…For measuring the brightness of the samples, they were mounted in a home built thermoluminescent setup described elsewhere [10]. The samples (typically a 13 mm diameter and 1 mm thick pellet composed of 100 mg of phosphor with 300 mg KBr), were attached to a sample holder which can be cooled with a stream of cold nitrogen-gas and heated with a heating cartridge.…”

X-ray excited luminescence of SrAl2O4:Eu,Dy at low temperatures

“…The released electrons recombine with Eu 3þ ion, thus resulting in excited Eu 2þ creation. The following radiative transition to the Eu 2þ ground state is the origin of the green luminescence observed [8,12,13]. However, in addition to thermally stimulated process, the creation of excited Eu 2þ luminescence center via electron tunneling was observed recently as well [14].…”

Counting the Photons: Determining the Absolute Storage Capacity of Persistent Phosphors

“…The field of persistent luminescent materials gained importance with the discovery of SrAl${}_2$O${}_4$:Eu,Dy by Matsuzawa et al [1], replacing ZnS:Cu,Co [2] as the benchmark afterglow phosphor. This green emitting phosphor shows afterglow for several hours after the excitation has stopped, and has been extensively investigated [3,4,5]. Two decades after the discovery by Matsuzawa et al, the list of afterglow phosphors has grown, and in addition to the alkaline earth aluminates it now also includes, among others, silicates and sulfides doped with a wide variety of activators, such as Eu${}^{2+}$ [6], Ce${}^{3+}$ [7,8] or transition metal ions [9].…”