Influence of Rare Earth Ions (REIs) on the Visible Emission of Magnesium Sodium Borate Glasses

Borate glass systems have been extensively studied for practical applications in optical display devices by virtue of their peculiar luminescence efficiency. However, the attainment of high emission from borate glass materials via apposite control of rare earth ions (REIs) contents remains a topical issue in Material Physics. In this paper, we report the influence of REIs (Dy 3+ , Eu 3+ , and Sm 3+ ) on multiple-colour emission of magnesium sodium borate (MSB) glasses fabricated by using the conventional melt-quenching method. These glasses were optically characterized via X-ray Diffraction (XRD), UV-VIS-NIR and Photoluminescence techniques. The XRD pattern confirms the amorphous nature of the as-prepared glasses. The absorption spectra disclosed several absorption bands at 347 nm ( 6 H 15/2 → 6 P 7/2 ) for Dy 3+ , 393 nm ( 7 F 0 → 5 L 6 ) for Eu 3+ and 403 nm ( 6 H 5/2 → 6 P 5/2 ) assigned for Sm 3+ respectively. Also, the emission spectra radiate at 463 nm ( 4 F 9/2 → 6 F 11/2 + 6 H 9/2 ), 612 nm ( 5 D 0 → 7 F J ) and 599 nm ( 4 G 5/2 → 6 H 7/2 ) for Dy 3+ , Eu 3+ , and Sm 3+ correspondingly, wherein Dy 3+ emits blue, yellow, and red light, Eu 3+ emits red light and Sm 3+ emits reddish-orange light. Finally, 1.0 mol% content of Dy 3+ , Eu 3+ , and Sm 3+ in MSB glasses was found to be optimal and hence considered the best optical host for colour display devices.


I. INTRODUCTION
lass is a non-crystalline solid with a short-range order of solids which can melt below the glass transition temperature [1,2].Among the distinct class of glasses, borate (B2O3) glass matrices are spotted as the most suitable host for rare earth ion doping [3][4][5][6].However, sodium oxide (NaO) incorporation in borate glass disclosed a unique superstructure intermediate range order (IRO) that makes them fundamentally interesting through composition variation or thermal and pressure history control [7,8].The addition of other network modifiers such as Magnesium oxide (MgO), to the sodium borate glass network can bring appealing changes in optical and physical properties.MgO being a very good network modifier can change the local symmetry around the borate network by changing BO3 units into BO4 and makes the glass stronger and more closely packed [9,10].Moreover, the existence of MgO may also reduce the hygroscopic nature allied with the borate host which is very crucial for many glasses to get stability against devitrification [11].Despite immeasurable studies on the impact of various dopants (rare earth ions, REIs), only a few authors have simultaneously reported the effect of three different REIs on a single glass host (12,13).Driven by this basis, herein we present the synthesis and characterization of magnesium sodium borate glasses to ascertain the impact of three divergent rare earth ions (REIs) like dysprosium (Dy 3+ ), europium (Eu 3+) , and samarium (Sm 3+ ) on their visible light emission performance.

A. Sample Preparation
The magnesium sodium borate (MSB) glass series with nominal composition of 20nao-xmgo-(80-x)b2o3 (with x =10, 20 and 30 mol%) for undoped and 20nao-30mgo-(50-x)b2o3-xre2o3 (with x = 0.1, 0.9 and 1.0 mol%) for doped samples were prepared by standard melts quench technique and the glass compositions designations alongside the digital image of the as-prepared glass samples are well-presented in Table I. 20 g of each sample was weighed using the analytical balance and thoroughly mixed in alumina crucible.The mixture was melted at 1100°c for 45 minutes and subsequently transferred to a low-temperature furnace and annealed at 350°c for 3 hours.

B. Sample Characterization
The amorphous nature of the prepared glass samples is determined using the Rigaku AX-2500 Advance X-ray diffractometer that is equipped with a Cu-K-β filter having a wavelength of 1.54 Å.It was calibrated to measure in the range of 2θ from 3° to 100° whereas the absorption spectra of all MSB glasses are exposed by using Shimadzu UV-3600 UV-VIS-NIR Spectrophotometer ranging from 200 to 800 nm.The emission spectra are analyzed using Horiba Fluoromax-4 Spectrofluorometer measured from 300 to 1000 nm.The excitation wavelength of the MSB glasses was varied depending on REIs (Dy 3+ , 347 nm, Eu 3+ , 394 nm, and Sm 3+ , 403 nm) to inspect their prominent visible emission.

A. XRD Analysis
The XRD pattern of the undoped and Dy 3+ , Eu 3+ , and Sm 3+ doped MSB glasses obtained in the 2θ range from 10° to 90° is epitomized in Fig. 1.Apparently, the absences of discrete peaks but the presence of broad peaks validate the amorphous nature of these glasses.A similar result was obtained in another borate host [3].
Fig. 1 The XRD pattern of selected MSB glass from each series

B. Absorption Spectra Analysis
The absorption spectra of MSB glasses with varying contents of REIs are shown in Fig. 2.
Table II.Comparison of the observed excitation and prominent emission wavelengths with reported data on similar glass systems.

IV. CONCLUSION
In-swift, Dy 3+ , Eu 3+ , and Sm 3+ singly doped MSB glasses have been successfully prepared by using a melt quenching route and optically analyze to comprehend their emission proficiency.The absorption spectra of each rare earth ion show that the most intense absorption bands for Dy 3+ , Eu 3+ , and Sm 3+ were located at 347 nm, 393 nm, and 403 nm respectively depending on the concentration.Meanwhile, the emission spectra demonstrate the highest emission intensity situated at 463 nm, 612 nm, and 599 nm for Dy 3+ , Eu 3+ , and Sm 3+ correspondingly where 1.0 mol% contents of Dy 3+ , Eu 3+ , and Sm 3+ in MSB glasses was identified as best host with dazzling emission.This revelation reflects the potency of the present glass system in solid-state lasers and colour display device construction.