Elsevier

Optical Materials

Volume 114, April 2021, 110937
Optical Materials

Research Article
Physical, structural and optical characterization of Dy3+ doped ZnF2-WO2-B2O3-TeO2 glasses for opto-communication applications

https://doi.org/10.1016/j.optmat.2021.110937Get rights and content

Abstract

A series of ZnF2-WO2-B2O3-TeO2 (ZWFBT) glasses doped with different concentration of Dy3+ ions were prepared by using the melt quench method. The non-crystalline behavior of as-quenched ZWFBTDy glasses was approved by XRD spectra. The presence of different functional groups were identified by monitoring FT-IR spectra of ZWFBTDy glasses. The Differential Scanning Calorimetry (DSC) was used to estimate glass transition temperature (Tg) and thermal stability (ΔT) of an un-doped glass along with doped glasses. Physical parameters were estimated for Dy3+ doped ZWFBT glasses by using the formula available in the literature. The energy band gaps of as-quenched ZWFBTDy glasses were estimated by using three different theoretical models such as Mott and Davis relation, Hydrogenic Excitonic Model (HEM), and Urbach analysis. The optical absorption spectra were used to estimate the bonding parameters (δ) for elucidating the kind of bonding amide Dy3+ ions and its nearby ligands in the as-quenched glasses. The obtained experimental data from optical absorption spectra were compared with theoretical data calculated in the ambit of the Judd-Ofelt (J-O) theory. The J-O intensity parameters were estimated and a similar trend was observed (Ω2>Ω6>Ω4 ) for the as-prepared ZWFBTDy glasses. The results obtained using J-O intensity parameters are found consistent with the bonding parameters. The radiative parameters such as branching ratio, radiative transition, radiative lifetime, total radiative transition, absorption, and emission cross-sections were evaluated and discussed. The gain coefficient was evaluated for the NIR transitions of as-quenched ZWFBTDy glasses. The obtained results suggested that the as-prepared ZWFBTDy glasses were auspicious candidates for laser emission and optical communication applications.

Introduction

During the past three decades, optical properties of lanthanide (La3+) activated materials are widely premeditated for their potential usage in various areas such as lasers, fiber communication, luminescent display devices, 3D memory devices, optical detectors, w-LEDs, and waveguides [[1], [2], [3], [4], [5]]. The wide absorption as well as luminescent spectra, easier manufacture procedure, less fabrication cost, makes the glass hosts more suitable than the crystalline hosts and has drawn the attention of researchers’ from the spectroscopic & technological perspective [6,7]. The design and development of an opto-communication device for the aforementioned uses necessitate the detailed examination of the physical, structural and optical properties of La3+ doped glasses. Such studies possess the evidence concerning radiative transition probability, lifetime and gain coefficient, etc. of La3+ doped glasses. The ligand fields formed by the glass host can create a significant impact on the physical, structural as well as optical properties of La3+ doped glasses. Moreover, a glass host having fewer phonon energies can enhance radiative properties and in turn possess a high gain coefficient for attaining effective lasers and optical fiber amplifiers [8,9].

The chemical composition of glasses plays an important role in imparting the unique luminescence characteristics. Oxide based glasses such as phosphate, borate and telluride glasses are known to have high luminescence. Amongst these, telluride glasses are most suitable because of high infrared transparency, low phonon frequencies, high refractive index, good corrosion resistance and high transmittance in visible and infrared regions [10]. TeO2 based glasses are appropriate for lasers, optical amplifiers and fiber optics, besides it, these hosts are extensively applicable in photonic crystal fibers; consequently, they are having potential use in nonlinear materials [[11], [12], [13]]. B2O3 is used due to low softening points, low crystallization point, low melting point and provides high RE ion solubility and easy processing [14]. BO3 triangles and BO4 tetrahedral units construct the borate network leading to the formation of stable groups like diborate, triborate, tetraborate, etc., but B2O3 is highly hygroscopic and susceptible to the atmosphere leading to instability. The development of glass hosts with TeO2 and B2O3 glass formers with the above said properties is very important for scientific as well as technical point of view. The introduction of TeO2 into B2O3 improves the refractive index along with the transparency of host glass [15]. Network modifiers like ZnF2 are then added to the glass composition to negate the hygroscopic nature of the sample and provide necessary thermal stability, lower transition temperature, lower rigidity and low toxicity [[16], [17], [18]]. Tungsten oxide provides stability in the glass structure. The addition of WO3 to the host glass recovers the mechanical as well as thermal strength along with chemical durability of TeO2 based host glass [19]. All the aforesaid properties offered by TeO2, B2O3, ZnF2 and WO3 encourage us to devise a germane system namely ZnF2-WO2-B2O3-TeO2 (ZWFBT) glasses for opto-communication.

Dy3+ doped glasses own distinctive optical properties and paved the way for the development of opto-communication. They have been captivated by many researchers owing to 4f electronic configuration and therefore highly applicable in fluorescent lamps, solid-state lasers, LEDs, optical amplifiers etc. Besides this, Dy3+ ions doped materials are proficient for electron trapping resources, single phase white light generation, mercury free fluorescent lamps, etc [20]. The Dy3+ doped materials exhibit emission in visible (blue and yellow) as well as NIR (1.32, 3.0 μm) regions and consequently opt for lasers, w-LEDs and optical transmission in fiber amplification [21].

Recently, Yuliantini and the group investigated lasing potentiality and scintillation properties of Dy3+ doped BaZnFBTe glasses [22]. They observed that the introduction of F2 (fluoride) into B2O3-TeO2 glasses makes the glasses more appropriate than barium zinc oxide for scintillation and photonics. Further, Kıbrıslı et al. studied spectroscopic investigations on Dy3+ doped telluride glasses for solid state lighting [23]. They obtained that the telluride glasses with Dy3+ ion content less than 0.5 mol% apt for w-LEDs with the highest CCT and CRI values. Okasha and co-workers detected the spectroscopic possessions of Dy3+ doped borate glasses using FTIR, absorption and Judd-Ofelt parameterization [24]. They observed that the above-said glasses are suitable for lasing potentiality and optical communication.

In this work, ZnF2-WO2-B2O3-TeO2 (ZWFBT) glasses doped with varying concentration of dysprosium (Dy3+) was synthesized and characterized using numerous spectroscopic techniques to elucidate their application in opto-communication. The as-quenched glass samples were characterized using XRD, FT-IR, DSC and optical absorption spectrophotometer. Various physical parameters such as densities, refractive indices, refraction losses, polaron radius, etc., were evaluated. The J-O intensity parameter has been estimated from the absorption profiles of the as-quenched glasses, which determine the radiative properties of Dy3+ activated ZWFBT glasses for the utility and the suitability in opto-communication.

Section snippets

Preparation of glasses

The ZWFBT glasses with composition 7ZnF2+9WO2+26B2O3+(58-x)TeO2+xDy2O3(where x = 0.1, 0.5, 1.0, 1.5 and 2.0 mol%) abbreviated as ZWFBTDy0.1, ZWFBTDy0.5, ZWFBTDy1.0, ZWFBTDy1.5 and ZWFBTDy2.0 have been prepared by the traditional melt quench method using the standard chemicals ZnF2, B2O3, TeO2, WO2 and Dy2O3. The chemicals in the aforesaid composition were weighed and mixed properly in an alumina crucible using agate with aceton as a wetting medium to get a homogenous mixture. This mixture was

Physical parameters estimation

The refractive indices and densities of the as-prepared ZWFBTDy glasses were measured experimentally and other physical possessions were evaluated by using admissible explanations that are existent in the literature [25,26] and tabulated in Table 1. By careful observation of Table 1, it has been investigated that the densities of as-quenched ZWFBTDy glasses intensify with growth in Dy3+ ions, which reveals the structural compactness in the glass network. The heavyweight of Dy2O3 i.e.,

XRD spectral analysis

XRD of as-quenched ZWFBTDy glasses is portrayed in Fig. 2. It is evident from Fig. 2 that the XRD of ZWFBTDy glasses is similar apart from the discrepancy in intensity. A broad hump in XRD identifies the glassy nature of the as-prepared ZWFBTDy glasses.

FT-IR spectral studies

The FT-IR spectrum of un-doped ZWFBT glass is recorded in the frequency range 500-4000 cm−1 as shown in Fig. 3(a). The FT-IR spectrum is used to inspect the presence of different functional groups in Dy3+ ions doped ZWFBT glasses. The obtained

DSC spectral study

The DSC thermogram of the un-doped ZWFBT glass sample was characterized in a 100–1000 °C temperature range with a 20 °C/min heating rate. Fig. 4 (a) disclose the various characteristics temperatures such as melting temperature (Tm), peak crystallization temperature (Tc), glass transition temperature (Tg), and liquidus temperature of ZWFBT glasses, which were found to be 406 °C, 593 °C, 746 °C, and 792 °C, respectively. Further, the DSC thermograms of the Dy3+ ion doped ZWFBTDy glasses were

Optical energy band gap evaluation

The UV–visible–NIR absorption spectra are used to evaluate the absorption coefficient (α) of the as-quenched ZWFBTDy glasses by using the following expressionα=1lln(100T)here, l shows the thickness of as-quenched ZWFBTDy glasses while T is the transmittance (in %). The plot between the absorption coefficient (α) and energy (hv) of as-quenched ZWFBTDy glasses is depicted in Fig. 5(a). Further, the optical band gap is a significant part as it explains the transitions of electronic band

Conclusion

The ZnF2-WO2-B2O3-TeO2 (ZWFBT) glasses doped with varying Dy3+ ions have been prepared via melt quench technique and their structural, thermal and optical properties were studied in detail. The addition of Dy2O3 in the as-quenched ZWFBT glasses has enriched the physical properties such as mounting the density, refractive index, average molecular weight, etc. and reducing the polaron radius, interionic distance, etc. A broad hump in XRD confirmed the non-crystalline behavior of as-quenched

CRediT authorship contribution statement

Sanju: Data curation, Writing - original draft. Ravina: Data curation, Writing - original draft. Anu: Formal analysis. A. Kumar:Formal analysis.V. Kumar: Formal analysis, Formal analysis. M.K. Sahu: Formal analysis. S. Dahiya: Resources. Nisha Deopa: Supervision, Validation, Writing - review & editing. R. Punia: Supervision, Validation, Writing - review & editing. A.S. Rao: Resources, Writing - review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The corresponding authors, Dr. Nisha Deopa and Prof. Rajesh Punia are thankful to Prof. R.B. Solanki, Hon'ble Vice-Chancellor, Chaudhary Ranbir Singh University, Jind, Haryana for his unconditional support, help and encouragement. One of the authors, Prof. A.S. Rao is grateful to the Department of Science and Technology (DST), Govt. of India, New Delhi for the award of a major research project (EMR/2016/007766) to him.

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