Contents lists available at ScienceDirect Optical Materials journal homepage: www.elsevier.com/locate/optmat Luminescent properties of Eu-doped calcium aluminosilicate glass-ceramics: A potential tunable luminophore Hamed Bouchouicha a,b,* , Gerard Panczer a , Dominique de Ligny c , Yannick Guyot a , Riadh Ternane b a Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622, Villeurbanne cedex, France b Laboratoire d’Application de la Chimie aux Ressources et Substances Naturelles et à l’Environnement (LACReSNE), Université de Carthage, Faculté des Sciences de Bizerte, 7021, Zarzouna, Bizerte, Tunisia c Universität Erlangen-Nürnberg, Department Werkstoffwissenschaften, Lehrstuhl für Glas und Keramik, D-91058, Erlangen, Germany ARTICLE INFO Keywords: Calcium aluminosilicate glass Glass-ceramics Raman Luminescence Eu 3+ Eu 2+ CIE coordinates ABSTRACT Eu-doped calcium aluminosilicate glass-ceramics have been successfully prepared from the initial calcium alu- minosilicate glass, containing 50 wt% of silica, under heat-treatment. Structural and optical properties of glass and obtained glass-ceramics were investigated. Control of crystallization using X-ray diffraction and Raman spectroscopy allowed to identify two main crystalline phases: anorthite [CaAl 2 Si 2 O 8 ] as the major phase and melilite [Ca 2 Mg 0.75 Al 0.5 Si 1.75 O 7 ] as the minor phase. Luminescent properties were investigated by emission spectra, lifetime measurements and color point analysis. The Eu 3+ ion emission was used as an environment probe in the initial glass and glass-ceramics. Additionally, the broad band emission due to 4f 6 5d 1 →4f 7 showed that Eu 2+ is incorporated into the crystalline phases after reduction of Eu 3+ during annealing. This in- corporation, increasing with time of heat-treatment, enhanced Eu 2+ luminescence. 1. Introduction White light emitting diodes (W-LEDs) are considered as a new generation of phosphor materials for many reasons such as long life- time, environmental benefits, low energy consumption and flexibility to many applications as displays or lighting [1–5]. One method to make W-LEDs is the combination of UV or blue LED chips with actually one, two or three phosphors materials. The first commercial W-LEDs consist of GaN-based blue chips and YAG: Ce 3+ yellow phosphor [6]. There- fore, it is interesting to develop suitable rare-earth elements (REE) ion doped material capable of generating white light under blue LED chips. REE ions have versatile applications and their properties are strongly host dependent [7–9]. Eu 3+ and Eu 2+ have found important applications. The Eu 3+ doped phosphors show orange-red emission by 4f→4f transitions whose positions are practically independent of li- gands. However, the relative intensity between those transitions is correlated with the local environment symmetry. While, the Eu 2+ doped phosphors show broad emission band with large cross sections by 4f 6 5d 1 →4f 7 transition depending on the ligands field. Because their typical emission spectra cover wide wavelength range from violet to yellow, the Eu 2+ doped phosphors become one of the most important components in the phosphors converting W-LEDs. For many years, REE ions doped calcium aluminosilicate (CAS) glass have been synthesized for different optical purposes. These OH - free glass prepared under vacuum atmosphere, present potential applica- tions as white light generation devices when particularly doped with Eu 2+ [10] and Eu 2+ /Eu 3+ [11] ions. Over these years, in order to increase luminescence efficiency, glass- ceramic may be used. These systems doped with REE ions possess ex- cellent characteristics from both glasses and crystals such, better thermal stability, lower production cost, low phonon energy and good crystal environment for REE ions [12–14]. Furthermore, it is desirable to combine advantages of glasses and crystal materials via developing glass-ceramics for W-LEDs with better luminescence intensity. In recent years, it was observed that devitrification in aluminosili- cate glass systems containing CaO, Al 2 O 3 and SiO 2 as the major com- ponents showed that crystallization occurs via surface [15]. Also, it was reported that addition of nucleating agent like TiO 2 and Fe 2 O 3 was effective to generate bulk crystallization [16]. In our SiO 2 eAl 2 O 3 eCaOeMgO glass system, without nucleating agents, crys- tallization achieved by simple heat treatment showed that crystal- lization is quite heterogeneous over surface sample [17], but only in https://doi.org/10.1016/j.optmat.2018.08.006 Received 27 May 2018; Received in revised form 1 August 2018; Accepted 5 August 2018 * Corresponding author. Laboratoire d’Application de la Chimie aux Ressources et Substances Naturelles et à l’Environnement (LACReSNE), Université de Carthage, Faculté des Sciences de Bizerte, 7021, Zarzouna, Bizerte, Tunisia. E-mail address: midoubou@hotmail.fr (H. Bouchouicha). Optical Materials 85 (2018) 41–47 0925-3467/ © 2018 Elsevier B.V. All rights reserved. T