In situ evolution of Ni environment in magnesium aluminosilicate glasses and glass–ceramics–Influence of ZrO 2 and TiO 2 nucleating agents A. Dugué a , O. Dymshits b , L. Cormier n,a , B. Cochain a , G. Lelong a , A. Zhilin b , S. Belin c a Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC), Sorbonne Universités-UPMC Univ Paris 06, CNRS UMR 7590, Muséum National d’Histoire Naturelle, IRD UMR 206, F-75005 Paris, France b NITIOM S.I. Vavilov State Optical Institute, 36/1 Babushkin St, Saint-Petersburg,192171 Russia, c Synchrotron Soleil, BP 48, 91192 Gif-sur-Yvette Cedex, France article info Article history: Received 16 September 2014 Accepted 16 November 2014 Available online 20 November 2014 Keywords: Glasses Crystal growth XAFS (EXAFS and XANES) X-ray diffraction Optical properties abstract The evolution of Ni 2 þ environment has been systematically investigated using optical and in situ X-ray absorption spectroscopy (XAS) to determine the influence of nucleating agents (TiO 2 and/or ZrO 2 ) during the formation of spinel in magnesium aluminosilicate glass–ceramics. The results were complemented by in situ X-ray diffraction data. According to XAS and optical spectroscopy, the nature of nucleating agents does not modify significantly the Ni environment in initial glasses. However, it has a relatively strong influence in the observed crystallization sequence. Ni 2 þ ions do not enter the Zr-containing crystalline phase of ZrO 2 or ZrTiO 4 but a Ni 2 þ coordination change from the fivefold coordinated sites, with a small amount of tetrahedral sites in parent glasses, to [6] Ni 2 þ and [4] Ni 2 þ sites in spinel (in glasses nucleated by ZrO 2 and/or TiO 2 ) or in β-quartz solid solutions (in glasses nucleated by ZrO 2 ) has been found. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction Transition metal (TM) ion-doped glass–ceramics can offer pro- mising active devices for efficient broadband optical amplification covering the whole optical communication range. Among TM ions, tetrahedrally coordinated Cr 4 þ [1,2], octahedrally coordinated Cr 3 þ [3,4] Bi ions in different valences and coordination states and octa- hedrally coordinated Ni 2 þ [5–8] can have broad emission band- widths (typically 4200 nm) in the near-infrared range from 1-1.7 μm. Ni 2 þ ions are mostly encountered in trigonal bipyramid and tetrahedral sites in oxide glasses [9–11], so that their emission efficiency is weak or non-existing in glasses compared to crystals. Conversely, Ni 2 þ ions strongly partition in octahedral sites in spinels [12]. This explains the growing interest to develop transparent na- nophase spinel glass–ceramics, which can be easily prepared, with low cost for mass production, compared to single crystalline coun- terparts [13]. Spinel crystallization has been mainly considered in aluminosilicate systems (SiO 2 –Al 2 O 3 –Li 2 O–ZnO–MgO) [1,5,13–25], demonstrating the possibility to obtain a broad IR luminescence due to Ni 2 þ in spinel phase [6–8,21–24,26–29]. Compared to single crystals, glass–ceramics offer a variety of environments for the TM as these latter may be localized in the remaining glass (that can have a composition different to the in- itial one), in various crystalline phases or at their interfaces. In order to predict, tailor and control the luminescence properties of the materials, the full identification of the TM sites, in particular the active sites, and their evolution with the heating treatment is necessary. Local (short-range order) information together with chemical selectivity can be obtained by optical absorption spec- troscopy and X-ray absorption spectroscopy (XAS) which are both sensitive to site geometry and cation-oxygen bond covalency. Optical transparency is a requirement for photonic applications and in order to obtain transparent nanophase glass–ceramics, the common nucleating agents (TiO 2 and ZrO 2 ) are added. They can be used together or separately to promote crystallization in volume, to decrease crystallization temperature and to increase nucleation kinetics [30–33]. Their role is to accelerate phase separation or lower the energy barrier of nucleation and they are usually asso- ciated with the first appearing nano-phase, i.e. ZrO 2 , TiO 2 , ZrTiO 4 or aluminotitanates. The role of these agents was particularly studied in the MgO–Al 2 O 3 –SiO 2 (MAS) ternary system [33–43], in which nucleation and internal bulk crystallization is achieved using TiO 2 and/or ZrO 2 . The MAS glass–ceramics are also well Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jpcs Journal of Physics and Chemistry of Solids http://dx.doi.org/10.1016/j.jpcs.2014.11.008 0022-3697/& 2014 Elsevier Ltd. All rights reserved. n Corresponding author. E-mail address: cormier@impmc.upmc.fr (L. Cormier). Journal of Physics and Chemistry of Solids 78 (2015) 137–146