Contents lists available at ScienceDirect Vacuum journal homepage: www.elsevier.com/locate/vacuum Luminescence properties of Eu 3+ activated Y 2 O 3 red phosphor with incorporation of Ga 3+ and Bi 3+ trace hertero-cations in the Y 2 O 3 lattice A. Yousif b , Babiker H. Abbas a,b , Vijay Kumar a,c , Anurag Pandey a , H.C. Swart a,* a Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein, ZA, 9300, South Africa b Department of Physics, Faculty of Education, University of Khartoum, P.O. Box 321, 11115, Omdurman, Sudan c Department of Applied Physics, Chandigarh University, Gharuan, Mohali, Punjab, India ARTICLE INFO Keywords: Y 2 O 3 :Eu 3+ /Ga 3+ /Bi 3+ ions Photoluminescence Cathodeluminescence ABSTRACT The luminescence characteristics of Eu 3+ doped Y 2 O 3 in the presence and absence of Bi 3+ /Ga 3+ trace ions prepared by the sol-gel combustion method were investigated. The results revealed that, the Bi 3+ and Ga 3+ ions have a signiﬁcant inﬂuence on the excitation position and emission bands intensity of Eu 3+ doped Y 2 O 3 . The cathodoluminescence (CL) intensity of the Y 2 O 3 :Eu 3+ incorporated with Bi 3+ /Ga 3+ ions has been considerably enhanced (ﬁve times), compared to the CL intensity of the unincorporated Y 2 O 3 :Eu 3+ samples. This phenom- enon was attributed to the energy exchange in the excitation bands of the Bi 3+ and Eu 3+ ions. 1. Introduction Phosphors are inorganic solid compounds having the capability to absorb energy and subsequently emit that as light when the excitation source is removed [1]. The desired colour of the light and the intensity of the phosphor are strongly depended on the luminescent center and the host's structure, which are considered as the main component of the phosphor. As an example, Y 2 O 3 is a good host for the rare earth ions such as Eu 3+ . The Y 2 O 3 :Eu 3+ is one of the famous red emitting phos- phor materials [2–4]. This phosphor is commonly used in tricolor ﬂuorescent lamps and ﬁeld-emission displays, because it has an eﬃ- cient luminescence under ultraviolet and electron-beam excitation [5]. One limitation of this phosphor is the position of the excitation bands, which are located below 300 nm. In some applications, it is desired to ﬁnd a red phosphor with excitation bands located at a lower energy with a wavelength around 350 nm. Modiﬁcation of the host's lattice structure by the introducing of hetero-cations, is one of the methods that can be used to shift the position of the excitation bands to lower energies. The change in the host structure sometimes gives a good lo- cation for the excitation bands, but the intensity of the phosphor is too low to be used for practical applications. In recent years, researchers tried to incorporate bismuth (Bi) ions as a sensitizer with the rare earth ions to improve their optical properties [6]. It has been reported by Wan el al [7]. That the appropriate amount of Bi 3+ could improve the optical properties of red phosphors due to the transfer of the absorbed energy from the Bi 3+ ions to the Eu 3+ ions. Other researchers have introduced even traces of Al and B ions into Y 2 O 3 :Eu 3+ phosphor and found a signiﬁcant enhancement in the luminescence eﬃciency, which was attributed to the change in the ﬁeld strength of the host [8,9,10]. Liu et al. [11] found that the luminescence intensity and quantum ef- ﬁciency of ZnB 2 O 4 :Bi 3+ ,Eu 3+ phosphor was much higher than that of ZnB 2 O 4 :Eu 3+ phosphor by co-doping Bi 3+ into the host via an energy transfer process. Park et al. [12] reported on a shift of the excitation band to a longer wavelength due to the energy transfer from Bi 3+ to Eu 3+ with an increase in the content of Bi 3+ in the YVO 4 :Eu 3+ phos- phor. On the other hand, Yousif el al [13,14] reported that, introducing an appropriate amount of Ga ions into the oxide host can aﬀect the luminescence properties of the Bi ions. To the best of our knowledge, no one studied the luminescence properties of Eu 3+ activated Y 2 O 3 red phosphor with the incorporation of Ga 3+ and Bi 3+ trace elements. In this study, the Y 2 O 3 :Eu 3+ phosphor with and without incorporation of the Ga 3+ and Bi 3+ trace elements in the Y 2 O 3 lattice were prepared using the sol-gel combustion method. The photoluminescence (PL) and cathodoluminescence (CL) properties were studied to understand the inﬂuence of Ga 3+ and Bi 3+ ions on the Y 2 O 3 :Eu 3+ phosphor. The energy exchange phenomenon involve in the present research is also discussed in detail. 2. Experiment details Yttrium nitrate (Y(NO 3 ) 3 .6H 2 O, 99.99% pure), Gallium nitrate (Ga (NO 3 ) 3 .6H 2 O, 99.999% pure) bismuth nitrate (Bi(NO 3 ) 3 .5H 2 O, 99.999% pure), Europium nitrate (Eu(NO 3 ) 3 .5H 2 O, 99.999% pure) and hydrated citric acid (C 6 H 8 O 7 .H 2 O, analytical grade) were used as https://doi.org/10.1016/j.vacuum.2018.05.054 Received 8 May 2018; Accepted 29 May 2018 * Corresponding author. E-mail addresses: swarthc@ufs.ac.za, traheel3@gmail.com (H.C. Swart). Vacuum 155 (2018) 73–75 Available online 30 May 2018 0042-207X/ © 2018 Elsevier Ltd. All rights reserved. T