Contents lists available at ScienceDirect Materials Science & Engineering B journal homepage: www.elsevier.com/locate/mseb Structural properties of Er 3+ doped lead zinc phosphate glasses Swarup Chowdhury a , Pabitra Mandal b , Subhankar Ghosh a, ⁎ a Department of Physics, St. Xavier’s College (Autonomous), 30, Mother Teresa Sarani, Kolkata 700016, India b Department of Physics, Narasinha Dutt College, 129, Belilious Road, Howrah 711101, India ARTICLE INFO Keywords: Phosphate glass Erbium doping Melt quenching FTIR ABSTRACT Structural properties are studied for some Er 3+ doped lead zinc phosphate glasses prepared by conventional melt quenching followed by heat-treatment at suitable temperature. Differential thermal analysis (DTA) confirms the glass transition near 150 °C and crystallization temperature of the glasses at about 430 °C. SEM pictures reveal grain growth similar to columnar one during annealing for the ceramic phase of the above glasses. XRD studies confirms the dominant phase of PbZnP 2 O 7 in the polycrystalline glass ceramics. From UV–VIS studies, different optical parameters like refractive index, electronic polarizability etc. indicate modified values. FTIR spectro- scopy shows the presence of various infrared bands of PO 4 3- and P 2 O 7 4- with transmission peaks at 480, 740, 910, 1071 and 1260 cm -1 respectively. The relative population of bending units of OePeO and O]PeO de- creases with the increase in Er 3+ content. A small increase in the population of asymmetric stretching of P]O bond is also observed. 1. Introduction Phosphate glass is an important class in the world of glass and glass ceramics for a number of its applications [1,2]. Alkali phosphate glass having the common composition of (M 1 ,M 2 ,M 3 ) 2 OP 2 O 5 where M stands for different alkali metals, are used as optical materials with nonlinear properties [3]. Among the broad class of phosphate glasses, ZnO based phosphate glasses have low glass-transition temperature in the region of 280 °C – 380 °C and significantly high chemical durability [4]. Addition of lead oxide (PbO) in phosphate glass increases the density and refractive index which in turn affects the optical properties of a glass [5]. Further, they have suitable high thermal expansion coefficients in the range of 12 × 10 -6 /°C and therefore find sealing applications [6]. Lead zinc phosphate glasses are also used as effective storage material for radioactive/nuclear waste [2]. The above glasses are colourless and the refractive index can be tailored in the range of n = 1.57 (x = 0) to 1.83 (x = 0.6), e.g., in the system (PbO) x (ZnO) 0.6 - x (P 2 O 5 ) 0.4 [7]. Recently, ZnO based phosphate glass is considered as an active substrate for use in waveguide lasers and amplifiers as phosphate glasses can absorb and retain high concentrations of rare earth (RE) materials [8]. It is well known that the structure of phosphate glasses is best de- scribed as a network of phosphate tetrahedra which are linked through covalent bonding of corner shared oxygen atoms, known as bridging oxygen atoms. Oxygen atoms that do not link two phosphate tetrahedra are called nonbridging. The ratio of bridging to non-bridging oxygen depends on glass composition. Phosphate glasses typically consist of long “polymer like” phosphate chains. The linked phosphate tetrahedra have one, two, three or four non-bridging oxygen atoms. These units can be classified using Q i terminology [7] where i represents the number of bridging oxygen atoms per tetrahedron. For example, a Q 2 tetrahedron links to two others through bridging oxygen in a phosphate chain anion, with Q 1 tetrahedra terminating the ends of the chains. The role of network modifying oxides in the glass is to break up or depo- lymerize the phosphate chains as the [O]/[P] ratio increases [9]. The phosphate chain and ring anions are linked by bonds between various modifying metal cations and the non-bridging oxygen; these bonds are more ionic in nature. A thorough survey of the reports on the structural and the optical properties of Lead Zinc Phosphate (LZP) glass system reveals studies on doping with different RE elements like Sm 3+ [8], Dy 3+ [10] and Tb 3+ [11]. Further, few studies are reported on the Er doped nanoparticle embedded Zinc Phosphate glass [12,13], Pb free zinc phosphate glass [14] etc. But reports on erbium (Er) doped LZP system are uncommon. This is the reason why Er is chosen as RE dopant in LZP system in this study to investigate their structural properties. https://doi.org/10.1016/j.mseb.2019.01.014 Received 30 November 2017; Received in revised form 2 December 2018; Accepted 15 January 2019 ⁎ Corresponding author. E-mail address: subhankar@sxccal.edu (S. Ghosh). Materials Science & Engineering B 240 (2019) 116–120 0921-5107/ © 2019 Elsevier B.V. All rights reserved. T