Contents lists available at ScienceDirect Corrosion Science journal homepage: www.elsevier.com/locate/corsci Decomposition of persistent luminescent microparticles in corrosive phosphate glass melt N. Ojha a , H. Nguyen a , T. Laihinen b , T. Salminen a , M. Lastusaari b,c , L. Petit a, ⁎ a Laboratory of Photonics, Tampere University of Technology, FI-33101 Tampere, Finland b University of Turku, Department of Chemistry, FI-20014 Turku, Finland c Turku University Centre for Materials and Surfaces (MatSurf), Turku, Finland ARTICLE INFO Keywords: Phosphate glasses SrAl 2 O 4 :Eu 2+ ,Dy 3+ microparticles Persistent luminescence Corrosion Decomposition ABSTRACT Findings on the decomposition of persistent luminescent (PeL) SrAl 2 O 4 :Eu 2+ ,Dy 3+ microparticles (MPs) in phosphate glass melt under static condition are reported. PeL phosphate glasses with the composition (50P 2 O 5 - 10Na 2 O-40SrO) (in mol%) were prepared by adding the MPs in the glass melt. The decomposition of the MPs occurs during the preparation of the glass and leads to changes in the Eu 2+ sites and to the formation of Eu 3+ which decreases the PeL properties of the glasses. The decomposition of the MPs depends on the temperature at which the MPs are added in the melt and also on the time before casting the melts. 1. Introduction There has been some interest during the past few years to process glass-ceramics (GCs) with persistent luminescence (PeL) properties as such GCs emit light for a long time (from seconds to hours) after the removal of the irradiation source [1]. These new materials can find applications as, for example, fluorescent light sources due to their high luminous efficiency, energy-saving, long lifetime and good features for protection of the environment [2]. PeL glass-ceramics were successfully obtained using the so called “Frozen sorbet method” developed by Nakanishi et al. [3]. This method was applied to the SrO-Al 2 O 3 -B 2 O 3 glass system in which SrA- l 2 O 4 :Eu 2+ ,Dy 3+ crystals precipitate [4]. These crystal seeds, which grow into microparticles (MPs), are formed by the ions from the glass. In these SrAl 2 O 4 :Eu 2+ ,Dy 3+ crystals, both Eu 2+ and Dy 3+ substitute for Sr 2+ . The Eu 2+ ions act as luminescent centers while the Dy 3+ ions are used to increase the duration of the persistent luminescence as they increase the number of energy traps in the structure [5]. However, with this “Frozen sorbet method”, the composition of the MPs depends on the composition of the glass matrix. Therefore, we developed an al- ternative route for the preparation of phosphate glasses with persistent luminescence properties [6]: PeL phosphate glasses were obtained by adding SrAl 2 O 4 :Eu 2+ , Dy 3+ microparticles (MPs) in glass batches prior to the glass melting. However, the MPs aggregate in the glasses leading to glasses with inhomogeneous persistent luminescence properties. Based on these results, our work has now been focused on the pre- paration of glasses with uniform persistent luminescence. Recently, an alternative approach, the direct doping of particles into tellurite-based glass melts, was developed to prepare glasses with better dispersion of particles in the glass [7,8]. The first step consists of melting the glass batch. Then, the temperature is reduced to the doping temperature to increase the glass viscosity. The particles are, then, added at this doping temperature, mixed into the melt and finally cast after a short dwell time to allow dispersion of the particles. Recently, we showed, for the first time to our knowledge, that this direct doping method could be used to process phosphate glasses with upconversion (UC) while using a low amount of Er 3+ and Yb 3+ (0.01 at% of Er 3+ and 0.06 at% of Yb 3+ )[9]. Our study suggested that it is crucial to un- derstand how the particles are corroded in the molten glass in order to control the dispersion and survival of the particles in the glass and so to prepare glasses with homogeneous luminescence properties. Surprisingly, the works concerning the corrosion behavior of glass melts have been realized only since the late 1950s and on pure metals such as Pt [10] and Fe [11] just to cite a few. The behavior of pure metals immersed in molten glasses in terms of corrosion rates and corrosion layers was found to depend on the glass composition and melt temperature [12]. Therefore, the investigation of the corrosion of other materials in phosphate glass melt is of great interest and brings new knowledge on the corrosion behavior of the glass melts. Here, SrAl 2 O 4 :Eu 2+ ,Dy 3+ microparticle (MPs) were added in https://doi.org/10.1016/j.corsci.2018.02.050 Received 30 August 2017; Received in revised form 15 February 2018; Accepted 21 February 2018 ⁎ Corresponding author. E-mail address: laeticia.petit@tut.fi (L. Petit). Corrosion Science xxx (xxxx) xxx–xxx 0010-938X/ © 2018 Elsevier Ltd. All rights reserved. Please cite this article as: Ojha, N., Corrosion Science (2018), https://doi.org/10.1016/j.corsci.2018.02.050