Persistent luminescence fading in Sr2MgSi2O7:Eu2+,R3+ materials: a thermoluminescence study

The fading of persistent luminescence in Sr2MgSi2O7:Eu2+,R3+ (R: Y, La-Nd, Sm-Lu) was studied combining thermoluminescence (TL) and room temperature (persistent) luminescence measurements to gain more information on the mechanism of persistent luminescence. The TL glow curves showed the main trap signal at ca. 80 degrees C, corresponding to 0.6 eV as the trap depth, with every R co-dopant. The TL measurements carried out with different irradiation times revealed the general order nature of the TL bands. The results obtained from the deconvolutions of the glow curves allowed the prediction of the fading of persistent luminescence with good accuracy, though only when using the Becquerel decay law. (C) 2012 Optical Society of AmericaTurku University FoundationTurku University FoundationJenny and Antti Wihuri Foundation (Finland)Jenny and Antti Wihuri Foundation (Finland)Academy of Finland [117057/2000, 123976/2006, 134459/2009, 137333/2010]Academy of FinlandCAPES (Brazil)CAPES (Brazil

DFT and synchrotron radiation study of Eu2+ doped BaAl2O4

The structural distortions resulting from the size mismatch between the Eu2+ luminescent centre and the host Ba2+ cation as well as the electronic structure of BaAl2O4:Eu2+(,Dy3+) were studied using density functional theory (DFT) calculations and synchrotron radiation (SR) luminescence spectroscopy. The modified interionic distances as well as differences in the total energies indicate that Eu2+ prefers the smaller of the two possible Ba sites in the BaAl2O4 host. The calculated Eu2+ 4f(7) and 4f(6)5d(1) ground level energies confirm that the excited electrons can reach easily the conduction band for subsequent trapping. In addition to the green luminescence, a weak blue emission band was observed in BaAl2O4:Eu2+,Dy3+ probably due to the creation of a new Ba2+ site due to the effect of water exposure on the host. (C) 2012 Optical Society of AmericaTurku University FoundationJenny and Antti Wihuri Foundation (Finland)Academy of Finland [123976/2006, 134459/2009, 137333/2010, 112816/2006/JH, 116142/2006/JH, 123976/2007/TL]Academy of Sciences of the Czech RepublicCzech research project [AVOZ10100521]European Community [RII3-CT-2004-506008]CNPqNanobiotec-Brasil RH-INAMIinctINAMIFAPESPCoimbra GroupCAPES (Brazil