Speaker
Prof.
Hendrik Swart
(University of the Free State)
Description
BaAl2O4:Eu2+,Dy3+ is the heaviest but the least efficient persistent luminescent material in the MAl2O4:Eu2+,R3+ series. Low efficiency may be due to the hygroscopic host material and/or polymorphic crystal structure [1]. Both may deteriorate the persistent excitation and emission through a change in the trap structure thus shortening the persistent duration. Charging of BaAl2O4:Eu2+,Dy3+ is rather slow, a steady state was achieved only after 30 s. Deconvolution of the thermoluminescence (TL) curves yielded a single trap with a depth of 0.8 eV after UV irradiation. Results agree well with studies on BaAl2O4:Eu2+,Dy3+ prepared with solid state and combustion methods [2]. 3D persistent excitation spectroscopy used in this study gives more detailed information than the simple TL measurements. The irradiation of BaAl2O4:Eu2+,Dy3+ with 200 to 500 nm UV-vis radiation has no effect on the shape of the TL glow curves consisting of a single band at 57 °C. The excitation spectra show little fine structure: at least two bands at 280 and 330 nm (max) with a shoulder at 380 nm. This structure may be due to the splitting of the 2D excited level of Eu2+. The use of free solar energy for excitation is thus limited. The 3D TL emission spectra show only one broad band at 500 nm despite two Ba2+ sites. The BaAl2O4:Eu2+,Dy3+ materials are interesting persistent phosphors though UV excitation is required. The shallow trap at 0.8 eV yields weak and short persistent luminescence at room temperature, as well. A stable crystal structure would be an advantage, too.
References
[1] J. Hölsä, H.C. Swart, L.C.V. Rodrigues, H.F. Brito, M. Lahtinen, M. Lastusaari, ESTAC-11, Aug. 17-21, 2014, Espoo, Finland.
[2] L.C.V. Rodrigues, R. Stefani, H.F. Brito, M.C.F.C. Felinto, J. Hölsä, M. Lastusaari, T. Laamanen, M. Malkamäki, J. Solid State Chem. 183 (2010) 2365.
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Primary author
Prof.
Jorma Hölsä
(University of Turku)
Co-authors
Prof.
Adrie J.J. Bos
(Delft University of Technology)
Prof.
Hendrik Swart
(University of the Free State)
Prof.
Lucas C.V. Rodrigues
(University of São Paulo)
Prof.
Marja Malkamäki
(University of Turku)
Prof.
Mika Lastusaari
(University of Turku)
Prof.
Pieter Dorenbos
(TU Delft)
