Dose effects on the long persistent luminescence properties of beta irradiated SrAl 2 O 4 :Eu 2þ , Dy 3þ phosphor M. Pedroza-Montero a, * , B. Castan ˜ eda b , M.I. Gil-Tolano a , O. Arellano-Ta ´ nori a , R. Mele ´ ndrez a , M. Barboza-Flores a a Departamento de Investigacio ´n en Fı ´sica, Universidad de Sonora, Apartado Postal 5-088, 83000 Hermosillo, Sonora, Mexico b Departamento de Fı ´sica, Universidad de Sonora, Apartado Postal 1626, Hermosillo, Sonora, Mexico article info Article history: Received 24 August 2009 Received in revised form 9 December 2009 Accepted 28 December 2009 Keywords: Strontium aluminate Persistent luminescence phosphors Electron traps abstract The SrAl 2 O 4 :Eu 2þ , Dy 3þ is a phosphor characterized by a long persistent luminescence (PLUM) when it is excited with UV–VIS light and ionizing radiation. In this paper, we study the PLUM behavior as a function of beta irradiation dose in the 0–650 Gy range with a fixed dose rate of 5 Gy/min. The PLUM intensity showed a complex decay behavior, exhibiting a near linear response in the 0–1.7 Gy low dose range and gradually increasing up to 160 Gy. The PLUM reached the saturation for higher doses (>275 Gy) with a slight decrease in the range of 300–650 Gy. In addition, a systematic PLUM enhancement was produced after a thermal cleaning procedure and irradiation at RT in a series of 10 cycles. The observed phenomenon may be related to a radiation-induced process of charge trapping accumulation, which is triggered by thermal stimulation during the irradiation stage. It improves the luminescent characteristics of SrAl 2 O 4 :Eu 2þ , Dy 3þ phosphors rendering them suitable for permanent display and illumination devices. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction The luminescent mechanism behind the PLUM of SrAl 2 O 4 :Eu 2þ has been modeled including the participation of electron traps and hole-recombination centers through mechanisms that consider the values of physical properties (activation energy of traps, quenching of luminescent centers, relaxation paths, etc.) and compare them to the experimental results (Aitasalo et al., 2004; Chang et al., 2006; Dorenbos, 2005, 2007; Nakazawa et al., 2006; Qiu et al., 2007). However, the exact luminescent model is far from being under- stood. An important consideration in all models is the role of the dopants and co-dopants, because a particular selection of them may increase the duration of persistent luminescence from seconds to hours (Nakazawa and Mochida, 1997; Yamamoto and Matsu- zawa, 1997). Besides, the thermal bleaching and the interaction of dopants with electron traps, recombination centers or the crystal lattice has particular significance because recent studies have related the PLUM to the lattice defects (Hoelsae et al., 2004) and their concentration ratios (Katsumata et al., 2006). Also, the effect of irradiation temperature and dose in PLUM behavior has been incorporated due to their capability of changing the luminescent response (Kamiyanagi et al., 2007; Kowatari et al., 2002) and allowing the generation of new charging processes from discon- nected electron traps (He et al., 2006; Jia, 2003). Recently, we have proposed a luminescent model for explaining TL/PLUM as a func- tion of irradiation temperature considering intermediate levels originated by the irradiation exposure/temperature cycles (Melendrez et al., 2009). In this paper, we study the PLUM of SrAl 2 O 4 :Eu 2þ , Dy 3þ exposed to beta ionizing dose in a broad range from 0 to 650 Gy. We have analyzed the three temporal processes in PLUM and tracked their behavior under different conditions of dose absorbed at RT. The experimental results provide experimental insights for a phenomenological model of the PLUM where the electron migration from (intrinsic and radiation-generated) deep electron traps may be a new source for a recharging process. 2. Experimental The samples of SrAl 2 O 4 :Eu 2þ , Dy 3þ phosphors were prepared with a solid reaction of SrCO 3 , Al 2 O 3 , Dy 2 O 3 and Eu 2 O 3 with a flux of B 2 O 3 . The crystals were pressed into pellets and then sintered at 1623 K for 2 h in an N 2 reducing atmosphere. The concentrations of Dy and Eu dopants were 1% and 0.5% mol, respectively. The purity of all components was 99.99%. Further details of the method of preparation of these phosphors is given elsewhere (Yen et al., 2000). The measurements of persistent luminescence were carried * Corresponding author. E-mail address: mpedroza@cifus.uson.mx (M. Pedroza-Montero). Contents lists available at ScienceDirect Radiation Measurements journal homepage: www.elsevier.com/locate/radmeas 1350-4487/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.radmeas.2009.12.046 Radiation Measurements 45 (2010) 311–313