ENHANCEMENT IN LUMINESCENT PROPERTIES OF RARE EARTH IONS DOPED BARIUM STRONTIUM ALUMINO BOROSILICATE GLASSES FOR PHOTONIC APPLICATIONS

Abstract

A variety of multipurpose and industrial applications can benefit from the usage of glasses, glass ceramics, and ceramics, three significant classes of engineering materials. Glasses and glass ceramics have garnered significant interest because of their benefits. Within the special class of amorphous solid-state materials, inorganic glasses are typically formed over a broad range of glass-former concentrations and are thermally stable. A significant amount of research has been done on rare earth (RE) doped glasses for near-IR lasers, broadband optical amplifiers, up-conversion luminescence temperature sensors, and solid-state lighting (SSL) applications since Snitzer's 1961 initial demonstration of the laser action of Nd3+ ions in barium crown glass. Additionally, a number of precursor glasses were used to create optical fibers that released infrared radiation. Recent advances in the lighting industry have benefited greatly and practically from advances based on solid-state lighting (SSL). SSL devices used relatively little energy and were compact, strong, and eco-friendly. The SSL based white light emitting diodes (w-LEDs) are better to other convectional light sources including incandescent lamps, electric bulbs, and fluorescent tubes because they are smaller, more ecologically friendly, have excellent color rendering, require less energy, and have a longer lifespan. The development of better white w-LED lighting sources has become essential for reducing artificial lighting's global energy usage. YAG: Ce 3+ phosphor and blue LED are now the building blocks of commercial w-LED production. The current generation of w-LEDs has a number of shortcomings, such as a halo effect, an inaccurate color temperature, and a low color rendering index. To get around the restrictions, RE activated glass can be used in place of phosphors. In addition, glass has some v special properties, such as strong chemical and thermal stability, high RE ion solubility, and an easy-to-produce approach. Given this, efficient RE activated glass could be advantageous for a variety of photonic devices, such as w-LEDs. One can adjust specific spectrum qualities by choosing the appropriate host glass composition or varying the concentration of RE ions in a glass. Referred to specific uses such as SSL as well as solid-state lasers, RE-doped glasses display unique optical properties in a range of host glasses such as chalcogenides, phosphate, borate, silicate, and telluride. The lasing features of glass hosts can be enhanced by using a good former, intermediates, and network modifier. Selecting the host glass with the right combination of RE ions for best lasing and optical properties is still a difficult task. Host glass, which has a relatively low phonon energy and raises the stimulated emission cross-section and quantum efficiency, is a dependable material for the development of lighting materials. On the basis of the aforementioned advantages, multipurpose and industrial applications of the RE doped glasses were selected of the current thesis work. The aim of research works is to enhance the luminescent properties of RE ions doped glasses for photonic applications. The goals of the research are being met by the several chapters. Every chapter is written such that it can be read on its own. Chapter 1: A clearer introduction, the reason for the problem, the motivation for the research, and a review of recent literature are all included in the first chapter. Based on the characteristics required for glass host, BaO-SrO-Al2O3˗B2O3-SiO2 (BaSrAlBSi) glass composition selected to synthesize, transparent, thermally and mechanically stable glass with exceptional photonic properties, which can directly be applicable in optical devices. This approach has involved a thorough exploration of the properties of the many chemical components present in the host glass. The usefulness of RE ions doped in glasses for use in vi photonic devices has been studied further. It has been discussed how the Inokuti-Hirayama (I-H) model is used to study the mechanics of luminescence degradation and energy transfer. The process of determining the CIE chromaticity color coefficients (x, y) from the luminescence spectra in order to evaluate the white light tunability has also been thoroughly explained. The examination of temperature-dependent emission indicates the value of thermal stability in the applications of produced glasses W-LEDs. Chapter 2: The experimental process used for producing RE-doped glasses and the methods for evaluating the glasses' luminous properties are the main topics of the second chapter. There is also a detailed discussion of the melt-quench process, which is used to create the as-prepared glasses. This chapter describes the use of many sophisticated experimental techniques, such as X-ray diffraction (XRD), UV-VIS spectrophotometer, Fourier-transform infrared spectroscopy (FT-IR), and fluorescence, to study various properties, including thermal, structural, photoluminescent, and colorimetric properties. Chapter 3: Transparent, Sm3+ doped and Sm3+/Eu3+ co-doped alkaline earth alumino borosilicate (AEAlBS) glasses have been synthesized by employing melt quenching process and explored their down-shifting luminescent properties for utility in visible red photonic devices applications. The non-crystalline nature of the as prepared glass was analyzed with help of XRD pattern, containing broad peak. Photoluminescence (PL) properties demonstrate the glasses were proficiently excited by near-UV with dominant peak centered at 402 nm. The emission spectra exhibit four emission peaks with an intense peak placed at 599 nm under 402 nm excitation. The optimum emission intensity was obtained for 0.5 mol% Sm3+ ions doped in AEAlBS glasses. Sm3+ ion works as effective sensitizer for Eu3+ activator ion in AEAlBS glasses and part of energy transfer (ET) from sensitizer (Sm3+) to activator (Eu3+) ions. The PL intensity of Sm3+ ion peaks were demises and enhance the Eu3+ ion peaks with Eu3+ ion co- vii doping in AEAlBS glasses under λex = 402 nm. The efficient ET from sensitizer to activator ions proved to be dipole-dipole in nature via employing Dexter's formula with Reisfeld's approximation. The experimental lifetime values calculated from the PL decay profiles are decreasing with surge in Eu3+ ion concentration in the as prepared glasses. I-H model applied to the PL decay profiles confirm the ET process responsible for decrease in experimental lifetimes as dipole-dipole in nature. The outcome of I-H model is in consonance with the result given by Dexter theory. The CIE coordinates for single Sm3+ doped glasses are falling in orange region, and gradually surge into red region by co-doping with Eu3+ ions in AEAlBS glasses. The temperature-dependent photoluminescence (TD-PL) emission analysis reveals that the PL intensity at 150°C and 200°C perseveres up to 94.34 and 91.30 % of the PL intensity at environmental temperature, respectively. All the obtained results contemplate the superiority of the multifunctional Sm3+/Eu3+ co-doped AEAlBS glasses for near UV triggered photonic device applications. Part of this work has been published in an international journal Journal of Non-Crystalline Solids 580 (2022) 121392 (Impact Factor: 3.20). Chapter 4: A series of Tb3+ activated transparent BaSrAlBSi glasses were prepared via melt quenching routes and detailed studied their optical characteristics for advanced laser and lighting appliances applications. The diffraction pattern defined the amorphous nature of the prepared transparent BaSrAlBSi glass. The UV visible spectrum shows the various absorption in n-UV visible and NIR range owing to Tb3+ ions. BSi:Tb glasses were proficiently near-UV excited, which emits blue, green, yellow and red light corresponding peaks situated at 487, 543, 587 and 623 nm, respectively. The maximum photoluminescence (PL) emission intensity was observed for 1.0 mol% Tb3+ doped BaSrAlBSi glass. Beyond the 1.0 mol% concentration of Tb3+ ions, quenching mechanism was recognized via applying the Dexter theory. The PL lifetimes were showing a decrease in decay time with upsurge in Tb3+ content. I-H model was viii used to identify the type of non-radiative energy mechanism, which is found to be dipole-dipole in nature. TD-PL characteristics demonstrate the very less effect of temperature dependency on PL intensity and shows the good thermal stability of BaSrAlBSi glass with 1 mol% of Tb3+ ions (BSi:1.0Tb) glass. The observed results anticipate that the direct utility of the as prepared transparent Tb3+ doped BaSrAlBSi glasses as n-UV pumped with green emitting constituent for photonic device applications. Part of this work has been communicated to an international journal Optical Materials (2024) (Impact Factor: 3.80). Chapter 5: A number of Tb3+ and Tb3+, Sm3+ incorporated BaSrAlBSi glasses were prepared, and their optical properties were carefully examined for use in high-tech lighting and laser applications. The transparent BaSrAlBSi glass's amorphous nature was established by the XRD pattern. The absorption profile demonstrates the various peaks from n-UV to NIR range caused by the Tb3+ as well Sm3+ ions in BaSrAlBSi glass. BaSrAlBSi glass with 1 mol% of Tb3+ ions (BSi:Tb1.0) glasses gives emission in blue, green, yellow and red light owing to the transition from 5D4 to various 7F(J = 6, 5, 4 & 3) under λex=379 nm. BSi:Sm1.0 glasses exhibits the emission spectra green to red region, caused by the transitions from 4G5/2 to 6H5/2, 6H7/2, 6H9/2, and 6H11/2 of the Sm3+ ions. The Tb3+/Sm3+ co-doped BaSrAlBS glasses exhibit a mixture of blue, green, and orange-red light when excited at 379 nm, whereas they red-orange light when excited at 402 nm. The PL lifetimes demonstrated a reduction in decay time as Sm3+ concentration increased in Tb3+ doped BaSrAlBSi glass. The sort of non-radiative energy process was determined using the I-H model, and it turns out to be a dipole-dipole in the environment. CIE coordinates show the green emission was tuned towards warm white region via co-doping of Sm3+ in Tb3+ doped BaSrAlBSi glasses. The strong thermal stability of 1 mol% of Tb and Sm doped BaSrAlBSi glass (BSi:TbSm1.0) glass is confirmed via temperature dependent emission profile, which reveals that temperature dependence on PL intensity has a very small impact. ix The observed results indicate that the transparent BSi:TbSm1.0 glasses as made will be directly useful for photonic device applications as n-UV pumped with the green warm white and orange emitting component. Part of this work has been published in an international Journal Optical Materials 145 (2023) 114446 (Impact Factor: 3.80). Chapter 6: A overview of the overall study effort and the conclusions drawn from the data are presented in sixth chapter of this dissertation. This chapter also looks at future directions for this study and how it could be used to inform future research directions.