Contents lists available at ScienceDirect Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/locate/jnoncrysol Structural and optical properties of TeO 2 -Li 2 O-ZnO-Nb 2 O 5 -Er 2 O 3 glass system N. Elkhoshkhany a, ⁎ , Samir Y. Marzouk b , Nourhan Moataz a , Sherif H. Kandil a a Department of Material Science, Institute of Graduate Studies and Researches, Alexandria University, 163 Horreya Avenue, Shatby 21526, Egypt b Department of Basic and applied science, Faculty of Engineering and Technology, Arab Academy of Science and Technology, Egypt ARTICLE INFO Keywords: Tellurite glasses Optical properties Er 3+ ions Judd-Ofelt ABSTRACT Quinary tellurite glass system in the percentages of 75TeO 2 –5Li 2 O–10ZnO–(10–x) Nb 2 O 5 –xEr 2 O 3 where (x = 0.0, 0.5, 1.0, 1.5, 2.0, and 2.8 mol%) have been prepared and characterized. Both Fourier-transform-in- frared (FTIR) and Raman spectroscopies were performed to study the structural changes correlated with the glass network. The thermal characteristics of the system were specified which showed a higher thermal stability (> 100 ° C) due to the formation of more bridging oxygen's (BO's) revealed by (FTIR) and Raman spectroscopies. The optical absorption spectra within near UV–visible regions were performed, and exhibited nine absorption bands centered around 1536, 977, 798, 653, 545, 524, 490, 450, and 443 nm corresponding to the 4 I 15/2 ground state to the various excited states 4 I 13/2 , 4 I 11/2 , 4 I 9/2 , 4 F 9/2 , 4 S 3/2 , 2 H 11/2 , 4 F 7/2 , 4 F 5/2, and 4 F 3/2 respectively. The same measurement also showed increasing values of the optical band gap (E g ) form 2.70 to 2.90 (eV) and decreasing the refractive index (n) from 2.48 to 2.42. Both the extinction coefficient data and the complex dielectric functions of the glasses were estimated. The different optical parameters were distinctly affected by increasing the Er 2 O 3 (mol %) and the structural changes. The radiative properties of the glass were calculated using J-O parameters. The Branching ratio (β) of 4 I 13/2 → 4 I 15/2 transition peaked at 1520.48 nm for Er 3+ ions has the highest value (1.000) also, the radiative lifetime (τ) of the same transition changed from 1.4510 to 1.8483. The gain cross-section of the laser transition level from 4 G 11/2 → 4 I 15/2 changed from 1.44 × 10 -20 to 1.92 × 10 -20 cm -1 in the existing glass system. The acquired results exhibited that the existent glass can be a good candidate in the fiber drawing and laser, non-linear optical applications. 1. Introduction TeO 2 -based glasses have been recently the subject of many types of research according to their promising mechanical, electrical, physical, optical, and magnetic properties as well their chemical durability; lower manufacturing temperatures, large refractive indices, high di- electric characteristics, and good optical transmission [1, 2]. All of these unique properties made the TeO 2 -glass a suitable material for optical applications like laser materials and nonlinear applications [3]. The TeO 2 -glasses are distinguished by their ability to have two struc- tural units, one is TeO 4 with the Te element positioned in trigonal bi- pyramids (tbps) and the other is TeO 3 with the Te element positioned in trigonal pyramids (tps) with a lone pair in both [4]. The TeO 2 cannot be vitrified on its own but it can with the aid of a network modifier such as alkaline earth metal, transition metal or rare earth oxides to easily form a glass. It was reported that the insertion of Nb 2 O 5 in tellurite glass stabilizes the glass matrix and it may have a dual modification role, one as a network former and the other as a network modifier [5] thereby enhances the thermal stabilization (as proved previously [6]). The inclusion of Er 3+ (as a rare earth metal) increases the chemical durability of the glass due to its lower oxidizing in the air as well its stability. Its addition makes the glass possess specific applications in the optoelectronics, glass fibers and also the medical field [7, 8]. The ad- dition of ZnO increases both the tendency of glass formation, refractive index while decreases the optical energy band gap [9]. Insertion of alkali oxides M 2 O (where M = Li, Na or K) to TeO 2 based glasses create more non-bridging oxygen's (NBO's) which result in decreasing the coordination number of the glass forming units and hence decreasing the glass strength [10]. The present system was chosen due to these oxides and doped with Er 3+ due to its advanced applications especially in photonics and laser [11, 12]. This research aims to report our results on the structural, optical properties of the prepared erbium-doped tellurite glass. All the results will be discussed with respect to increasing Er 2 O 3 . https://doi.org/10.1016/j.jnoncrysol.2018.08.011 Received 27 May 2018; Received in revised form 8 August 2018; Accepted 9 August 2018 ⁎ Corresponding author. E-mail address: Elkhoshkhany@alexu.edu.eg (N. Elkhoshkhany). Journal of Non-Crystalline Solids xxx (xxxx) xxx–xxx 0022-3093/ © 2018 Elsevier B.V. All rights reserved. Please cite this article as: Elkhoshkhany, N., Journal of Non-Crystalline Solids (2018), https://doi.org/10.1016/j.jnoncrysol.2018.08.011