SrAl 2 O 4 :Eu 2þ (1%) luminescence under UV, VUV and electron beam excitation M. Nazarov a , S. Mammadova b, e, * , D. Spassky c , S. Vielhauer d , S. Abdullayeva b, e , A. Huseynov e , R. Jabbarov b, e a Institute of Applied Physics, Academie Street 5, Chisinau MD-2028, Moldavia b G. M. Abdullayev Institute of Physics, Azerbaijan National Academy of Sciences, 33 G. Javid Avenue,1143 Baku, Azerbaijan c Skobeltsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University,119991, Moscow, Russia d Institute of Physics, University of Tartu, W. Ostwaldi Str.1, 50411, Tartu, Estonia e Research Center for Hi-Technologies (RDCHT), MCHT, Baku, Azerbaijan article info Article history: Received 14 September 2017 Received in revised form 24 October 2017 Accepted 1 November 2017 Keywords: SrAl 2 O 4 :Eu 2þ Combustion method Photoluminescence Cathodoluminescence Synchrotron radiation Thermally stimulated luminescence abstract This paper reports the luminescence properties of nanosized SrAl 2 O 4 :Eu 2þ (1%) phosphors. The samples were prepared by combustion method at 600  C, followed by annealing of the resultant combustion ash at 1000  C in a reductive (Ar þ H 2 ) atmosphere. X-ray diffraction (XRD), photo luminescence (PL) and cathodoluminescence (CL) analysis and thermal stimulated luminescence (TSL) method were applied to characterize the phosphor. For the first time a peak at 375 nm was observed in CL spectra of SrAl 2 O 4 :Eu 2þ (1%) nanophosphors. Luminescence excitation spectra analysis have shown that this peak is related to crystal defects. Also in TSL curve one strong peak was observed in the region above room temperature (T ¼ 325 K), which is attributed to lattice defects, namely oxygen vacancies. A green LED was fabricated by the combination of the SrAl 2 O 4 :Eu 2þ (1%) nanosized phosphor and a 365 nm UV InGaN chip. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Due to high quantum efficiency in the visible spectral region [1], good stability, color purity, excellent physical and chemical prop- erties, SrAl 2 O 4 :Eu 2þ alkaline earth aluminates are very useful in preparation of pc LEDs [2,3]. In addition, due to their excellent luminescence properties, they also have potential applications in fluorescent lamps, plasma display panels and also can be utilized as persistent luminescence materials [4e6]. Usually two emission bands at 445 and 520 nm are observed in SrAl 2 O 4 :Eu 2þ . At room temperature the blue band is quenched and only green band is observed. The origin of these bands has been the subject of discussions for many years. Poort et al. [7] explained these two emission bands with the preferential orientation of d orbitals of Eu 2þ ion on Sr sites. Clabau et al. [8] explained blue emission band with charge transfer from the ground level of the 4f 7 configuration of Eu 2þ to the valence band. More recently, Botter- man et al. [9] reported a detailed investigation of the origin of both emission bands in SrAl 2 O 4 :Eu. In spite of the similarity in oxygen coordination, differences in bond lengths to the oxygen ligands for the two sites and in coordination number were used to explain the difference in emission and excitation spectra. Nowadays it is generally accepted that these two bands are attributed to emission from Eu 2þ ions placed in the two different lattice sites (Sr1, Sr 2) in crystal structure of SrAl 2 O 4 . In this paper, Eu 2þ doped SrAl 2 O 4 nanophosphors were syn- thesized by energy effective, fast and low-cost combustion method. Homogeneous, high crystallinity and good morphology samples were obtained as a result of the synthesis. In this paper, a photo- luminescence (PL) analysis was carried out for Eu 2þ doped SrAl 2 O 4 aluminates under UV-VUV excitation. The results of the photo- luminescence (PL) and cathodoluminescence (CL) of SrAl 2 O 4 :Eu 2þ (1%) nanophosphors were compared and discussed. Experimental results prove that the peak at 375 nm in CL spectrum is related to crystal defects. TSL glow curve peaks at 220 and 325 K are explained by existence of the crystal structure defects, namely oxygen vacancies. * Corresponding author. G. M. Abdullayev Institute of Physics, Azerbaijan Na- tional Academy of Sciences, 33 G. Javid Avenue,1143 Baku, Azerbaijan. E-mail address: samiras416@gmail.com (S. Mammadova). Contents lists available at ScienceDirect Optical Materials journal homepage: www.elsevier.com/locate/optmat https://doi.org/10.1016/j.optmat.2017.11.001 0925-3467/© 2017 Elsevier B.V. All rights reserved. Optical Materials 75 (2018) 448e452