IR@CGCRI - Central Glass and Ceramic Research Institute (CSIR)
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Phosphor in Glass (PiG) and Glass-ceramic Composite: Future Prospects for High-Performance WLEDs
No full textThe demand for energy-efficient, thermally stable, and spectrally tunable white light-emitting diodes (WLEDs) has led to intensive research into advanced phosphor materials. Commercially, W-LEDs are fabricated by combining GaN-based blue chip with luminescent layer comprising YAG: Ce3+ yellow phosphor in resin (PiR). However, due to their chromatic aberration and poor white light performance, the widened applications of W-LEDs in medical lighting is limited. At present, various fluorescent systems and photoluminescence-tunable strategies are actively being investigated using a variety of techniques. Phosphor-in-glass (PiG) and rare-earth ion (REI) doped glass andglass-ceramic composites have emerged as promising candidates for nextgeneration white light-emitting diodes (W-LEDs), owing to their superior thermal stability, optical performance, and structural reliability compared to conventional phosphor-in-resin (PiR) systems1 . In this study, two complementary approaches are explored to enhance the performance of W-LEDs. At first, Ce³⁺ :Y3Al5O12 (YAG)-based PiG composites were fabricated using ZnO– Na2O–Bi2O3–B2O3–SiO2 borosilicate glass matrix which has low softening point and closely matching refractive index with the index of phosphor. Notably, the fabricated PiG composites exhibited excellent thermal stability, retaining 90% of their luminescence intensity at 175°C, while the conventional phosphor-in-resin (PiR) systems could retain only 70%. Parallelly, Dy3+ - doped BaO–MgO–La2O3–Al2O3–SiO2 glass has been synthesized and converted them to glassceramics composite to havebetter thermal stability, low phonon energy, and good crystal environment for REI. The formation of BaAl2Si2O8 crystalline phases provided a favorable crystalline environment for Dy³⁺ ions, resulting in enhanced white light emission due to yellow at 580 nm (4 F9/2 → 6H13/2) along with blue emissions at 479 nm (4 F9/2 → 6H15/2) under excitation at 351 nm. Photoluminescence intensity was found to be 3–6 times higher in glass-ceramics compared to the precursor glass, accompanied by improved thermal and structural stability. Colorimetric analysis showed emission coordinates leaning toward the warm white region (X= 0.3606, Y=0.3814) indicating suitability for human-centric lighting applications. These two material strategies demonstrate the practical synergy between PiG and REI-doped glass-ceramics in addressing key limitations of commercial W-LEDs, such as poor thermal tolerance and limited color tunability. Their high efficiency, color tunability and durability make them strong candidates for solid-state lighting applications, including those requiring precise CCT control and long-term reliability
Separation of Magnesia from Waste MgO-C Refractory Fines Powder by Chemical Leaching Process
No full textMagnesite is a crucial raw material used in the production of refractory materials, which are known for their resistance to high temperatures, corrosion, and alkalis. However, the global supply of high-quality magnesite is limited, and countries like India, which have significant reserves, still face a shortage due to the magnesite being in impure forms. As a result, India imports millions of tons of magnesite annually from other countries. In industries such as steel and iron production, where refractories are essential, the demand for high-grade magnesia is increasing, but the supply is shrinking.
This research focuses on recovering magnesia from used refractory waste. In many research it has been observed that in recycling of waste refractory there is large agglomerates can be used upto 50% while, the fine powders were typically discarded. Our study reveals that up to 86% of magnesia can be recovered from these discarded fine powder through chemical leaching process by two different roots. After observing the result of XRD, TGA-DTA and by manual method the presence of periclase is about 90% in carbon magnesia fines powder which can recovered.in this study microstructure of this recovered Mg also observed The recovered magnesia has commercial applications, contributing to both environmental sustainability and the efficient use of resources. This approach offers a promising solution to the challenges of magnesite supply and waste management in the industry. This process not only helps reduce waste but also makes use of a material that is otherwise overlooke
Synthesis and Characterization of Er2O3-Doped Y2O3 Nanoparticle Incorporated Optical Fiber for Use as Optical Amplifier
No full textErbium oxide (Er2O3)-doped optical fibers (EDF) are well-known for their applications in optical amplification at 1550 nm. In this study, we present the synthesis of Er2O3-doped yttrium oxide (Y2O3) nanoparticles (NPs) using a homogeneous coprecipitation technique and their integration into optical fibers for enhanced optical amplification. A series of NP samples with varying Y/Er molar ratios were synthesized to identify the optimal composition for incorporation into optical fibers. X-ray diffraction (XRD) analysis revealed that the nanoparticles crystallize in a cubic geometry (space group Ia3) with crystallite sizes ranging from 20 to 41 nm. These sizes increased approximately to 90 nm as the calcination temperature was raised from 1000°C to 1400°C. Field emission scanning electron microscopy (FESEM) corroborated the XRD results, while high-resolution transmission electron microscopy (HRTEM) confirmed the crystalline structure and an average particle size of approximately 100 nm. Photoluminescence studies showed that emission and excitation intensities were functions of the Y/Er molar concentration ratio and calcination temperature, with the lifetime extending up to 6.86 ms for a sample with a 0.25:0.01 Y2O3:Er2O3 ratio calcined at 1400°C. To assess the performance of the synthesized NPs, an optical preform was prepared using the Vapor Phase Delivery (VPD) method combined with the Solution Doping (SD) technique. The preform was then drawn into fiber, and its amplification performance was evaluated. The resulting fiber demonstrated efficient amplification with a gain of 14.9 dB with respect to 0 dBm input signal at 1550 nm under 150 mW pump power from 9 m active fiber, indicating its potential as a gain medium for constructing erbium-doped fiber amplifiers (EDFAs)
Charge Carrier Dynamics in Semiconductor–cocatalyst Interfaces: Influence on Photocatalytic Activities
No full textElectron transfer dynamics at semiconductor-cocatalyst interfaces are critical for efficient solar fuel generation, including water splitting, pollutant degradation, CO2 reduction, and NH3 production. These interfaces facilitate charge separation, suppress recombination, and enable photoexcited charge carriers to transfer to active sites for photocatalytic reactions. The formation of Schottky or Ohmic junctions, energy band alignment, and surface properties significantly influence charge transfer efficiency. Advances in theoretical modeling, such as density functional theory (DFT), and experimental techniques, including ultrafast spectroscopy, have provided valuable insights into these processes. Understanding and optimizing these dynamics is essential for developing high-performance photocatalytic systems to harness solar energy and address global energy demands sustainably.This review offers a concise explanation of charge transfer mechanisms at semiconductor-cocatalyst interfaces, explored through various experimental methodologies and theoretical frameworks.Exploring the underlying mechanism will open new avenues for advancing high-performance semiconductor photocatalytic technologies.The conclusion sheds light on the challenges and promising opportunities for enhancing the understanding and investigation of interfacial electron transfer dynamics in semiconductor-cocatalyst systems
Dual Active Site Mediated Photocatalytic H2 Evolution Through Water Splitting using CeO2/PPy/BFO Double Heterojunction Catalyst
No full textPhotocatalytic water splitting generates hydrogen from water and sunlight, but one bottleneck for widespread usage is the poor performance of semiconductor photocatalyst materials. Manipulating the surface of a catalytic material by introducing different components can tune phase composition and extend the catalytic activity by delayed charge recombination, superior charge transfer, and enhanced light harvesting. A double heterojunction fabricated using CeO2 nanoparticles directly deposited on polypyrrole (PPy) nanofibers and then Bi2Fe4O9 (BFO) nanosheets have been grown on CeO2/PPy with a significant improvement in visible light absorption. A high photocurrent density of 5.5 µA cm−2 with more negative Flat band potential (−0.47 V vs Ag/AgCl) has been obtained for CeO2/PPy/BFO compared to single heterojunction CeO2/PPy (~1.9 µA cm−2 and −0.42 V vs Ag/AgCl). Lowering of charge transfer resistance (Rct) values from 612 kΩ, to 488 kΩ and 415 kΩ andlonger charge carrier lifetimesare of 4.8, 5.8, and 7.3 µs for CeO2, CeO2/PPy and CeO2/PPy/BFO respectively implying facile charge carrier separation with enhanced interfacial band bending after construction of double heterojunctions.Remarkably, CeO2/PPy and CeO2/PPy/BFO demonstrated 32and 71 times higher H2 generation, respectively than pure CeO2. Based on the possible band edge positions of semiconductors, a double heterojunction n-n-Z−Scheme charge transfer pathway has been proposed. Our demonstration provides a paradigm to improve catalytic performance for water splitting through surface engineering of semiconductor photocatalysts
Modelling of a Lyot filter based Mamyshev oscillator
No full textUtilizing a Lyot filter (LF) as one of the spectral filters, a new architecture of Mamyshev Oscillator (MO) has been presented at the 1.06-mu m region. The Ginzburg-Landau equation (GLE) has been solved numerically and the feasibility of obtaining a stable single pulse state from the oscillator has been checked. A possible architecture of the LF is presented and the tunability of the LF is achieved by introducing stress-induced birefringence (SIB). As the transmission window of the LF shifts, the spectral overlap between two filters also varies. Various types of states have been obtained as the solution of GLE depending on the spectral overlap between two filters. Attributes of each pulsing state have been presented and the intra-cavity spectral and temporal evolution has also been shown and discussed accordingly. The results confirm that in an optimized parameter space, stable single pulse state can be achieved from an LF-based MO and the pulse possesses properties of `amplifier similariton'. The compressibility of the output pulse has also been checked numerically and it is worth mentioning that the pulse can be compressed near to its transform-limited duration
Fabrication and Characterization of Silicon Carbide Ceramic Filtration Media Via Recycling of Waste Red Mud
No full textA porous silicon carbide (SiC) ceramic filter was prepared at 1000◦C using waste
red mud (RM), SiC, pore-forming agent, and catalyst. The influence of sintering temperature, RM content, and pore former on the mechanical performance
and the porosity of porous ceramics were investigated, and based on the result
optimal processing parameters were selected. The air and water permeability
tests were carried out at room temperature. The stability of the ceramic filter
under thermal shock and chemical treatment was investigated and corroded
samples were characterized. The ceramic was prepared using optimized processing parameters obtained with a flexural strength of 65.36 MPa at a porosity of
30.15 vol.% and demonstrated good performance in terms of pure water flux, oil,
and turbidity removal efficiency from industrial wastewater. The filtration and
permeation results indicated that the SiC filter prepared in this study is suitable
for various applications, particularly in the remediation of oil-polluted wate
Hybrid Antiresonant Negative-Curvature Optical Fibers: Theoretical Analysis and Sensing Application
No full textIn this paper we developed the understanding of a guidance mechanism of hybrid antiresonant negative-curvature fiber. We elucidated how the loss and cutoff wavelengths of core-guided modes depend on the lattice tube thickness and diameter for this fiber. We also derived an approximate expression to calculate the cutoff wavelengths for this hybrid antiresonant negative-curvature (core having higher refractive index than cladding) fiber. Finally, we explored the application of hybrid antiresonant fiber, proving its superior sensing capabilities compared to conventional hollow-core antiresonant fiber
A Roadmap towards Research and Development on Specialty Glasses for Strategic and SocietalApplications
No full textOver the years, several indigenous technologies have been developed by CGCRI to address the nation's needsin crucial sectors,particularly those where the material/technology is under embargo and high reliance on imports exists.Currently,CSIR-CGCRI is actively involved technology developmentfor the strategic sectors such as optical glass development (for ISRO), radiation shielding window glass (RSW), glass bid fornuclear waste immobilization and laser glass (for DAE), chalcogenide glasses for night vision camera (for DRDO)and high strength glass-ceramic armors (for DRDO/MoD).Further, glasses with multifunctional activities like thermally stable antibacterial bioactiveglasses,ferroelectric/anti-ferroelectric glass-ceramics for energy storage and phosphor in glass forLED applicationsare being explored. Sustainable value-added products (like foam glasses)are being developed by utilizing different types of glass wastesthrough bothconventionalmelting and microwave heatingtechniques. Thus, the research work aiming atthe development of awide domain of specialty glasses having specific applications in strategic, healthcare, electronics and societal segments envisages a direction towards “Atmanirbhar Bharat”
Influence of metal organic framework glasses on thermoelectric properties of AgSb0.96Zn0.04Te2 alloy
No full textIn recent years, a significant number of chalcogenides-based thermoelectric (TE) materials have been investigated theoretically and experimentally. However, the efficiency of TE materials is often limited by physical and chemical stability issues. Therefore, it is crucial to identify additive materials that can reduce thermal conductivity and improve the efficiency of crystalline TE materials. One well-known approach to lower thermal conductivity is introducing porosity into the material structure, which helps scatter phonon energy. Metal -organic framework (MOF) crystalline materials, known for their porosity and physical and chemical stability, offer unique advantages in TE applications. In this study, we investigate the influence of 20 weight% amorphous Zeolitic Imidazolate Framework (ZIF)-62 to p -type AgSb0.96Zn0.04Te2 (ASTZ), a well-known TE material. We synthesized composites, ASTZ, ASTZ-Zn, and ASTZ-Co, by sintering ASTZ with amorphous ZIF-62(Zn) and ZIF-62 (Co) respectively. The addition of amorphous ZIF-62(Zn) leads to a significant enhancement in the Seebeck coefficient of ASTZ increasing from 151 mu V/K to 229 mu V/K at 586 K. Moreover, the thermal conductivity of the ASTZ TE materials drops drastically from 0.491 Wm -1 K-1 to around 0.22 Wm -1 K-1 at 623 K with the addition of either amorphous ZIF-62(Zn) or ZIF-62(Co). Remarkably, ASTZ containing amorphous ZIF-62(Zn) achieves a maximum thermoelectric figure of merit (zTmax) of approximately 0.078 at 573 K, surpassing any MOF-based thermoelectric material reported to date. These findings highlight the potential of amorphous ZIF-62 as an effective additive for enhancing the properties of thermoelectric materials