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In this work, the visible luminescence of P 2 O 5 -KF-Al 2 O 3 glasses with Tm 2 O 3 was studied. The Tm3+ ion can have a strong blue emission, which allows the development of LEDs in this color region. This study refers to the synthesis of oxyfluorophosphate glasses, 38P 2 O 5 +(50-x)KF+12Al 2 O 3 +xTm 2 O 3 (PKAl:Tm), with x = 0.25, 0.50, 0.75, and 1.00 mol%, by the melt-quenching method. The prepared materials showed amorphous characteristics verified by XRD data. The absorption spectra shown six main bands characteristic of Tm3+ ions, from ground state 3H 6 to excited levels 3F 4 , 3H 4 , 3H 5 , 3F 3,2 , 1G 4 and 1D 2 , in which the intensities increased with the concentration of Tm 2 O 3. In the FTIR spectra, it was verified that the profiles of the PKAl samples are similar to glasses based on phosphate systems. The Judd-Ofelt parameters were calculated, where for PKAl glasses the trend was Ω 2 >Ω 4 >Ω 6. The excitation spectra of PKAl:Tm glasses shown an intense band centered at 358 nm (3H 6 →1D 2). The luminescence spectra with excitation at 358 nm shown two bands at 453 nm (1D 2 →3F 4), and 480 nm (1G 4 →3H 6); the highest emission intensity was observed to the sample doped with 0.75 mol% of Tm 2 O 3. The calculated CIE diagram shown that the doped samples have coordinates close to the primary blue color, which favors the application for the development of blue LEDs and wLEDs. The decay curves for the 1D 2 level were fitted by single exponential with lifetime values decreasing with increasing concentration of Tm 2 O 3. These results show that the PKAl:Tm glasses are potential candidates for applications in LEDs. [Display omitted] • 38P 2 O 5 -(50-x)KF-12Al 2 O 3 -xTm 2 O 3 glasses, x = 0.25, 0.50, 0.75, and 1.00 mol%. • The optical parameters, transition probability and radiative lifetimes were evaluated using the Judd-Ofelt theory. • CIE coordinates appeared in the deep blue regions under 357 excitation, with main emission at 454 nm. • Oxyflorophosphate glasses doped with Tm 2 O 3 are candidates for photonic applications in blue emitters. [ABSTRACT FROM AUTHOR]

The photoluminescence characteristics of praseodymium (Pr 3+ ) doped zirconia/polyethylene glycol (ZrO 2 /PEG) samples were studied using optical absorption and emission spectra. The optical properties were theoretically analysed using standard and modified Judd-Ofelt (J-O) models. The oscillator strength of the observed transitions and J-O intensity parameters were calculated using these J-O models. The radiative properties such as radiative transition probability ( A T ), branching ratio ( β R ), stimulated emission cross-section ( σ e ) and gain band width ( σ e × Δ λ e f f ) for the excited states of Pr 3+ in ZrO 2 /PEG composite have been determined. The experimental branching ratios obtained from the emission spectra were compared with the theoretical values. The excitation spectra of Pr 3+ doped samples show overlapping of Pr 3+ excitation peak at 448 nm at the end of the broad excitation band of the host, indicating the charge transfer between the host and Pr 3+ ions. Luminescence decay analysis confirmed concentration quenching in the prepared samples and the lifetime values are found to be in the microsecond range. [ABSTRACT FROM AUTHOR]

In this paper, structural and optical properties of WO 2.72 thin films implanted by 150 keV Ni ions having ion fluences in the range of 1015 to 1016 ions/cm2 have been investigated. Structural investigations (Raman and XRD) suggest the formation of the crystalline monoclinic phase of pristine films. However, after ion implantation, the crystalline quality degrades as a function of ion fluences, and complete amorphization is observed at highest fluence. Further, the bandgap decreases upon ion implantation as a result of band tailing effect. Optical investigation under UV excitation delineates the existence of NUV, band-to-band transition and blue green emission bands in WO 2.72 thin films. Implantation-assisted Ni doping blueshifted the new NUV emission peaks due to the enhancement in free electron concentration in the conduction band (CB). The overall hue of the emitted light investigated using Commission International de l'Eclairage (CIE) diagram demonstrates the transition from light to deep blue region upon Ni implantation. • Structural and optical properties of WO 2.72 thin films implanted with Ni ions were studied. • Amorphous films are obtained at high Ni fluences. • Multiple radiative transitions due to intrinsic and implantation induced defects were obtained. • Implantation-assisted doping of Ni leads to the production of oxygen vacancies. • The CIE coordinates depicts the tuning of color from light blue to deep blue. [ABSTRACT FROM AUTHOR]

Sr 3−2 x Sm x Na x B 2 SiO 8 phosphors were synthesized by the solid-state reactions. X-ray diffraction, diffuse reflection, photoluminescence excitation and emission, as well as fluorescence decay measurements were utilized to investigate the structural and spectral properties of the samples. The results indicated that Sr 3−2 x Sm x Na x B 2 SiO 8 phosphors could be efficiently excited by the near-ultraviolet light to realize a novel reddish orange luminescence corresponding to the characteristic transitions 4 G 5/2 → 6 H J (J = 5/2, 7/2, 9/2, 11/2) of Sm 3+ ions, with a maximum intensity at 600 nm. Based on the theoretical calculation, the dipole–dipole interaction was dominantly involved concentration quenching of Sm 3+ in the phosphors, and the critical transfer distance ( R c ) was determined to be 13.59 Å. Furthermore, Judd-Ofelt analysis was applied to evaluate three phenomenological Judd-Ofelt intensity parameters ( Ω λ , λ = 2, 4, 6), and in turn radiative properties such as radiative transition probabilities ( A R ), radiative lifetimes ( τ R ) and fluorescence branching ratios ( β R ) for the excited 4 G 5/2 luminescent level of Sm 3+ ions were determined. Upon 402 nm excitation, the composition-optimized Sr 2.90 Sm 0.05 Na 0.05 B 2 SiO 8 exhibited the preferable photoluminescence intensity and CIE coordinates of (0.534, 0.448). These results suggest that the Sm 3+ -doped Sr 3 B 2 SiO 8 phosphors are competitive as the reddish orange-emitting phosphor-converted materials for application in near-ultraviolet-pumped LEDs. [ABSTRACT FROM AUTHOR]

Abstract: Glasses having compositions 20CdO⋅xBi2O3⋅(79.5− x)B2O3 (15⩽ x ⩽35) doped with 0.5mol% of Sm3+ and Nd3+ ions were prepared by melt quench technique. The amorphous nature of the glasses was confirmed by X-ray diffraction studies. The spectroscopic properties of the glasses were investigated using optical absorption and fluorescence spectra. The structural investigations of these glasses were carried out by recording the Fourier transform infrared spectra. The Judd–Ofelt intensity parameters Ωλ (λ =2, 4, 6) and other radiative properties like radiative transition probability, radiative life time, branching ratio and stimulated emission cross-section of the prepared glasses have been calculated. The variation of Ω 2 with Bi2O3 content has been attributed to changes in the asymmetry of the ligand field at the rare earth ion site and to the changes in their rare earth oxygen (RE-O) covalency. The shift in the hypersensitive band shows that the covalency of the RE-O bond increases with increase of Bi2O3 content, and it is attributed to the increased interaction between the rare earth ions and the non-bridging oxygens (NBO’s). The radiative transition probabilities of the rare earth ions are large in cadmium bismuth borate glasses, suggesting their suitability as a potential candidate for laser application. Further, the FTIR results reveal that the glasses have BO3, BO4 and non-bridging oxygen as local structure. [Copyright &y& Elsevier]

Abstract: The spectroscopic properties of tellurite glasses of composition (in mol%) TNKNd: (70− x)TeO2–15Nb2O5–15K2O–xNd2O3 (x =0.1, 1.0, 1.5, 2.0 and 2.5) and TNLNd10: 69TeO2–15Nb2O5–15Li2O–1.0Nd2O3 and lithium metaborate glass of composition LBNNd10: 89LiBO2–10Nb2O5–1.0Nd2O3 have been investigated using absorption and emission spectra and decay curve analysis. An energy level analysis has been carried out considering the experimental energy positions of the absorption and emission bands, using the free-ion Hamiltonian model. The spectral intensities have been calculated by using the Judd–Ofelt theory and in turn the radiative properties such as radiative transition probabilities, emission cross-sections, branching ratios and radiative lifetimes have been estimated. The decay curves at the lower concentrations are exponential while they show a non-exponential behavior at higher concentrations (⩾1.0mol%) due to energy transfer processes. The effective lifetimes for the 4F3/2 level are found to decrease with increase in Nd2O3 concentration for all the glasses under investigation. The non-exponential decay curves have been well-fitted to the Yokota–Tanimoto model with S =6, indicating that the nature of energy transfer is of dipole–dipole type and energy migration also plays an important role. The results obtained have been compared with Nd3+-doped phosphate, fluorophosphate, lead borate, tellurite, germanate and silicate glasses and Nd3+-doped YAG ceramic and Ca2Nb2O7 crystals. [Copyright &y& Elsevier]

Abstract: This article reports the effect of mixed alkalis on the optical absorption and emission spectra of Sm3+ and Dy3+ doped chloroborate glass matrices of the compositions 69.5B2O3 xLiCl(30− x)NaCl0.5R2O3 and 69.5B2O3 xLiCl(30− x)KCl0.5R2O3 (where R=Sm and Dy and x =5, 10, 15, 20 and 25). Using Judd–Ofelt theory, the spectral intensities and Judd–Ofelt intensity parameters (Ω 2, Ω 4 and Ω 6) were obtained from the measured absorption bands of the spectra. Using these intensity parameters, total radiative transition probabilities (A T), radiative lifetimes (τ R), branching ratios (β) and peak emission cross-sections (σ P) were obtained for the two rare earth ions in these two glass matrices. Variation of these parameters with x in the glass matrix has been discussed. It is found that for Sm3+ ion, the transition, 4G5/2 → 6H9/2 shows highest emission cross-section and is maximum at x =10mol% in lithium–sodium and at x =20mol% in lithium–potassium glass matrices. For Dy3+ ion, the transition, 4F9/2 → 6H13/2 shows highest emission cross-section and is maximum at x =20mol% in lithium–sodium and at x =10mol% in lithium–potassium glass matrix. [Copyright &y& Elsevier]

Abstract: Structural and spectroscopic properties of neodymium doped sodium borate and fluoroborate glasses of composition (in mol%) (99− X) B2O3 + XNa2O+1Nd2O3, X =49.5, 39.5 and 29.5 and 49.5B2O3 + XNa2O+(49.5− X) NaF+1Nd2O3, X =0 and 24.75 have been investigated using XRD, FTIR, absorption and emission spectra and decay curve. The XRD of the glasses confirm their glassy nature and the FTIR spectra reveal the presence of BO3 and BO4 units along with the strong OH− groups in the glasses. The UV–vis-NIR absorption spectra were used to calculate the bonding parameters ( and δ), to identify the ionic/covalent nature of the glasses. The spectral intensities have been calculated by using Judd–Ofelt analysis and inturn used to estimate radiative properties such as radiative transition probabilities, radiative lifetimes, branching ratios, peak stimulated emission cross-sections. Branching ratios and stimulated emission cross-sections show that the 4F3/2 → 4I11/2 transition of the glasses under investigation has the strong emission around 1060nm. The decay from the 4F3/2 level of Nd3+ ions is found to be single exponential. Multiphonon relaxation and quenching due to OH− groups play a governing role in the luminescence quenching of 4F3/2 level of Nd3+ ions in the titled glasses. The results obtained are compared with reports on similar glasses. [Copyright &y& Elsevier]

Abstract: Glasses having composition 20ZnO·xBi2O3·(79− x)B2O3 (15⩽ x ⩽35mol%) and doped with 1mol% Sm3+ ions have been prepared by melt quench technique. Optical absorption and fluorescence spectra have been recorded. Judd–Ofelt approach has been applied for the f ↔ f transition of Sm3+ ions to evaluate various intensity parameters (Ω 2, Ω 4, Ω 6). The variations in intensity parameters, radiative transition probabilities and hypersensitive band positions with composition have been discussed. The variation of Ω 2 with Bi2O3 content have been attributed to change in the asymmetry of the ligand field at the rare earth ion site and to the changes in their rare earth–oxygen (RE–O) covalency, whereas the variation of Ω 6 is found to be strongly dependent on nephlauxetic effect. The shift of the hypersensitive band shows that the covalency of the RE–O bond increases with increase of Bi2O3 content due to increased interaction between the Sm3+ ion and non-bridging oxygens. The radiative transition probabilities for the Sm3+ ions are large in zinc bismuth borate glasses, suggesting their suitability as laser material. [Copyright &y& Elsevier]

Alkaline-Earth Boro Tellurite (AEBT) glasses (AEBT) activated with trivalent neodymium (Nd3+) ions were made by employing conventional melt quenching technique to explore their structural details, optical and photoluminescence (PL) properties. Energy Dispersive X-ray spectroscopy (EDX), absorption, fluorescence and fluorescence decay were performed to identify their feasibility for photonic applications. Judd-Ofelt (J-O) studies used for the absorption spectral features reveals larger values for Ω 2 and high radiative transition rates in AEBT glasses. The emission spectra of different concentrations of Nd3+ ions doped AEBT (AEBT: Nd3+) glasses show three transitions 4F 3/2 → 4I 9/2 , 4F 3/2 → 4I 11/2 and 4F 3/2 → 4I 13/2 at the wavelengths 887 nm, 1064 nm, and 1334 nm respectively. Among the observed transitions, 4F 3/2 → 4I 11/2 is the intense one observed in near - infrared (NIR) and is useful for lasing action at 1064 nm. The optical absorption, fluorescence and decay spectral studies, reveals that one mol% of Nd3+ ions concentration is quite suitable in AEBT glasses (AEBTNd1.0) to generate lasing action at 1064 nm suitable for NIR photonic broadband amplification applications. • EDX studies of AEBTNd1.0 glass revealed the chemical composition of the titled glasses. • The Judd-Ofelt analysis exposed the covalent nature of the Nd–O bond and low symmetry around Nd3+ ions in the glass network. • The transition 4F 3/2 → 4I 11/2 at 1064 nm has the highest stimulated emission cross-section values, branching ratios values for the AEBT glass doped with 1.0 mol% of Nd3+ ions. [ABSTRACT FROM AUTHOR]

Multi-component phosphate glasses with various Nd 2 O 3 content have been prepared using conventional melt-quenching technique. X-ray diffraction was carried out to study the structure of the prepared samples and it was found that all the obtained samples are amorphous. Electrostatic F (2) , F (4) , F (6) , and spin–orbit parameters have been determined from the absorption spectra. Judd-Ofelt theory has been used to analyze and evaluate the radiative transition probability, branching ratio, and radiative lifetime for the metastable level 4 F 3/2. Luminescence spectra and experimental lifetimes give information regarding the absence of chemical clustering and suggest that the physical clustering is negligible making the glass a suitable candidate for photonic applications. Image 1 [ABSTRACT FROM AUTHOR]