[en] Lithium Lead Alumino Borate (LiPbAlB) glasses doped with Dy³⁺ ions with varying concentration were synthesized by using the melt quenching technique to understand their feasibility in solid state lighting and laser devices. From the absorption spectra, bonding parameters (δ) were evaluated to understand the nature of bonding between Dy³⁺ ions and its surrounding ligands. Judd-Ofelt intensity parameters estimated from the experimental oscillator strengths were used to evaluate various radiative parameters for the fluorescent levels of Dy³⁺ ions. From the decay curves, the experimental lifetimes were measured and coupled with the radiative lifetimes to evaluate the quantum efficiency. The decay profile changes from exponential to non-exponential with increase in Dy³⁺ ion concentration resulting decrease in experimental lifetimes. Inokuti-Hirayama model applied to the decay spectral profiles confirm dipole-dipole interaction responsible for their conversion from exponential to non-exponential. By exciting the glasses with different n-UV radiations, the CIE chromaticity coordinates and correlated color temperatures (CCT) were calculated to understand the utility of as-prepared glasses in cool white light generation. From the evaluated radiative parameters, CIE co-ordinates, CCT temperatures, emission cross-sections, quantum efficiency and confocal images, it was observed that LiPbAlB glass with 0.5 mol% Dy³⁺ ions are more suitable for the development of w-LEDs and Lasers.

[en] Highlights: • ZSFBSi glasses doped with Sm³⁺ ions were prepared by melt quench technique. • Under 402 nm excitation the as-quenched glasses exhibit intense orange-red emission. • I–H model and Dexter theory reveal dipole-dipole interaction between Sm–Sm ions. • Calculated CIE coordinates are fall in orange-red region of visible spectrum. • 1.0 mol% of Sm³⁺ ions in these glasses are apt for orange-red luminescent devices. Augmenting the photoluminescence (PL) properties of Samarium (Sm³⁺) doped Zinc Strontium fluoro-borosilicate glass (ZSFBSi glass) by varying the Sm³⁺ ions concentration unlocks new prospects for their application as luminescent devices. This paper presents absorption, photoluminescence (PL), energy transfer and color chromaticity parameterization of ZSFBSi glass doped with Sm³⁺ ions concentrations. The Judd-Ofelt (J-O) theory in correlation with absorption as well as PL spectra leads to the estimation of radiative parameters of the excited luminescent states of Sm³⁺ ions needed to understand the luminescent potentiality of the as-prepared glasses. The absorption spectral data reveals the nature of bonding between Sm³⁺ ions and oxygen ligands in the as-quenched glasses as ionic and the result is consistent with the J-O analysis. The PL spectra of as-quenched glasses exhibit greenish-yellow, orange-red, light red and red color ascribed to ⁴G_5/2 → ⁶H_5/2, ⁶H_7/2, ⁶H_9/2, ⁶H_11/2 emission bands at 563, 599, 646 and 706 nm, respectively. The PL intensity enhances with an escalation in Sm³⁺ ions content until 1.0 mol% and reduces thereafter, owing to a proficient energy transfer (ET) process. The Dexter theory and Inokuti-Hirayama (I–H) model identified the foremost ET process associated with the as-quenched glasses as dipole-dipole in nature. The CIE color coordinates (x, y) and Correlated Color Temperature (CCT) were calculated to cognize the effectiveness of as-quenched glasses in radiative cool white emission. The estimated branching ratios, emission cross-sections, gain bandwidth, quantum efficiency, optical gain, color coordinates and CCT finally reveals that the as-quenched glasses can be used in luminescent devices and amide all, 1.0 mol% Sm₂O₃ in ZSFBSi glass is highly appropriate for white LEDs as well as orange-red luminescent devices.

[en] Terbium ions (Tb³⁺) doped Lithium Lead Alumino Borate (LiPbAlB) glasses with the chemical composition 10Li₂O – 10PbO – (10-x) Al₂O₃ – 70B₂O₃ – xTb₂O₃ (where x = 0.5, 1.0, 1.5, 2.0 and 2.5 in mol%) were synthesized via melt quench method and characterized by absorption, photoluminescence (PL) and PL decay spectral measurements. The Judd-Ofelt (J-O) intensity parameters evaluated from the oscillator strength values are further used to evaluate the radiative parameters for the prominent fluorescent levels (⁵D₄→⁷F_j) of Tb³⁺ ions. The intensity of all the emission bands increases up to 2 mol% of Tb³⁺ and beyond concentration quenching took place. The decay profiles of ⁵D₄ show single exponential for lower concentration and non-exponential for higher concentration resulting decrease in experimental lifetime (τ_exp) with increase in rare earth ion concentration. Such decrease in τ_exp and decay conversion from single to non-exponential has been attributed to the cross-relaxation processes and subsequent concentration quenching observed. The Inokuti-Hiryama (I-H) model applied to the decay spectral profiles confirms the energy transfer process between Tb³⁺-Tb³⁺ ions as dipole-dipole in nature. Higher values of stimulated emission cross-section, quantum efficiency, gain bandwidth and optical gain obtained for ⁵D₄→⁷F₅ transition of LiPbAlB glass with 2 mol% of Tb³⁺ ions suggests its suitability for green lasers. The CIE-chromaticity co-ordinates, color purity (CP) and correlated color temperature (CCT) confirms the suitability of these glasses in tricolor w-LEDs.

[en] Highlights: • BAZN glasses with Dy³⁺ ions were prepared using melt quench technique. • Under n-UV excitation the BAZN glasses show white light emission. • Energy transfer through cross-relaxation leads to concentration quenching. • Calculated CIE coordinates are close to the commercial w-LED. • 0.5 mol% of Dy³⁺ in these glasses are apt for cool white light generation. - Abstract: The Dy³⁺ ions doped Na₂O-ZnO-Al₂O₃-B₂O₃ (BAZN) glasses with variable doping concentrations were synthesized by melt-quenching technique. The XRD pattern reveals amorphous nature of the as-synthesized glass. The FT-IR spectrum reveals various stretching and bending vibration of aluminates, borate and some other groups. The emission spectra exhibit two intense bands at around 482 nm (blue) and 575 nm (yellow) corresponding to the ⁴F_9/2 → ⁶H_15/2 and F_9/2 → ⁶H_13/2 transitions respectively. The CIE chromaticity coordinates of the as-synthesized glasses are lying in white region and in proximity to the coordinates for white light specified by National Television Standard Committee and commercial phosphor converted white light emitting devices. The decay profile of BAZN glasses showed bi-exponential behavior due to the energy transfer mechanism from excited donor ion to unexcited acceptor ion. The above-mentioned studies show potential of the as-synthesized Dy³⁺ doped BAZN glasses in solid state lighting applications.

[en] Barium lead alumino fluoro borate (BaPbAlFB) glasses doped with Dy³⁺ ions were prepared by using melt quenching technique and characterized using various spectroscopic techniques to understand their usage in photonic devices. The SEM and EDX spectral studies were performed on the as prepared glasses to understand the glassy nature and elemental analysis respectively. The weight loss in the BaPbAlFB glass has been studied by the TGA. Judd-Ofelt (J-O) theory has been applied to the measured oscillator strengths of the absorption spectral features to evaluate radiative parameters for the prominent emission transitions of Dy³⁺ ions in BaPbAlFB glasses. The photoluminescence (PL) spectral measurements show concentration quenching beyond 1.0 mol% of Dy³⁺ ions in the as prepared glasses. The decay profiles observed for higher concentration of Dy³⁺ ions in these glasses are well fitted to Inokuti-Hirayama (IH) model to understand the energy transfer mechanism involved in the as prepared glasses. The experimental lifetimes (τ_exp) measured from the decay spectral features are correlated with radiative lifetime (τ_R) values to understand the quantum efficiency (η) of the as prepared glasses. From the PL spectra, colorimetric parameters such as CIE coordinates, correlated color temperature (CCT) and yellow-to-blue (Y/B) intensity ratios have been estimated to understand the usage of these glasses in photonic devices such as white LEDs and lasers.

[en] Highlights: • Borate glasses with Sm3+ ions were synthesized by melt quenching technique. • Under 402 nm excitation Borate glasses show reddish orange luminescence. • Energy transfer through cross-relaxation leads to fall in decay time of Sm3+ ions. • I-H model confirms energy transfer between Sm3+ ions as dipole-dipole in nature. • 1 mol% Sm3+ ions in these glasses are apt for red photonic device applications. - Abstract: This work describes mainly the optical absorption, photoluminescence (PL) and decay spectral properties of Sm³⁺ ions doped borate glasses to understand their possible usage in tricolor w-LEDs and lasers.The XRD spectrum recorded for an un-doped glass confirms glassy nature of the as prepared glass. The Judd-Ofelt (J-O) intensity parameters evaluated from experimental oscillator strengths were used in estimating the various radiative parameters. Under 402 nm excitation, the PL spectra exhibit intense emission at 600 nm for which the decay spectral profiles were recorded.The decay profiles are converting from single exponential to non-exponential with increase in Sm³⁺ ion concentration ensuing decrease in experimental lifetimes which may be attributed to the efficient energy transfer through cross-relaxation process. The non-exponential decay curves fitted to I-H model reveals the interaction between the Sm³⁺ ions as dipole-dipole in nature. From the evaluated emission cross-sections, quantum efficiency, branching ratios and CIE co-ordinates, it is concluded that 1 mol% Sm³⁺ ions in these glasses are aptly suitable to fabricate reddish-orange luminescent devices.

[en] Samarium ions doped barium lead alumino fluoro borate glasses were prepared by conventional melt quenching technique and characterized by using various spectroscopic techniques. The amorphous nature and functional groups present host glass were confirmed by XRD and FT-IR spectra respectively. From the measured oscillator strengths the Judd-Ofelt (J–O) parameters were evaluated and subsequently used to estimate various radiative properties for the prominent fluorescent levels. The PL spectra show three transitions ⁴G_5/2→⁶H_5/2, ⁶H_7/2, and ⁶H_9/2 at 565 nm, 602 nm and 650 nm in greenish yellow, reddish orange and red regions respectively. The experimental lifetimes correlated with radiative lifetimes to calculate quantum efficiency of the as prepared glasses. The CIE chromaticity coordinates measured establishes reddish orange emission from the as prepared glasses. Based on the emission cross-sections, branching ratios, quantum efficiency and CIE coordinates, it is concluded that the Sm³⁺ ions doped as prepared glasses are aptly suitable for reddish orange optoelectronics device applications.

[en] Highlights: • NaBiSrP glasses with Dy³⁺ ions were prepared by using melt quench technique. • Under 350 nm excitation the NaBiSrP glasses give white emission. • Energy transfer through dipole-dipole interaction leads to concentration quenching. • Calculated CIE coordinates are fall in white region and close to commercial pc-LED. • 1.0 mol% of Dy3+ ions in these glasses exhibits 89.17% quantum efficiency. -- Abstract: This paper focus on spectroscopic analysis of Sodium Bismuth Strontium Phosphate (NaBiSrP) glasses doped with dysprosium (Dy³⁺) ions using X-ray Diffraction (XRD), Raman Spectroscopy, Fourier Transform-Infrared (FT-IR) Spectroscopy, Photoluminescence (PL) Spectroscopy and decay spectral measurements. Excitation spectra of the glasses under 575 nm emission possess a sharp band corresponding to ⁶H_15/2 → ⁶P_7/2 transition (350 nm). Subsequently, emission spectra recorded under 350 nm excitation exhibit sharp bands at 480 and 575 nm. The Judd-Ofelt (J-O) theory has been applied to the measured energies of the absorption bands/oscillator strengths to study various radiative parameters such as radiative and total transition probabilities (A_R &A_T), branching ratios (β_R) and radiative lifetimes (τ_R) for the prominent fluorescent levels of Dy³⁺ doped NaBiSrP glasses. It was observed that glass D has got highest value of Ω₂ signalling high symmetry of crystal field of Dy³⁺ ions and a maximum intensity for hypersensitive transition. PL decay analysis reveal experimental lifetimes of ⁴F_9/2 energy level under 350 nm excitation decreases with increase in Dy³⁺ ion concentration indicating the energy transfer between Dy³⁺ ions. The Inokuti-Hirayama (I–H) curve fitting was also done for the glass with the highest Dy³⁺ ion concentration showing dipole-dipole interaction. From the above-mentioned results, it is apt to say that the as synthesized phosphate glasses doped with Dy³⁺ ions are quite suitable for designing the white light emitting diodes (wLEDs) and other optoelectronic devices.