Gd2O3-modulated borate glass for the enhancement of near-infrared emission via energy transfer from Gd3+ to Nd3.

(Li2O)0.20(SrO)0.30(Nd2O3)0.01(B2O3)0.49-x(Gd2O3)x, where x = 0, 3, 5, 7, and 10 mol%, glass was melt-quenched to test it as a laser source in the near-infrared (NIR) region. The structural modification, absorption spectra, Judd-Ofelt (J-O) parameters, luminescence spectra, radiative laser parameters, lifetimes, XRD, and FTIR spectra were studied. Luminescence spectra excited at λexc = 584 nm revealed the highest intensity peak at 1073 nm due to the transition of 4F3/2 → 4I11/2. An important phenomenon of concentration quenching was observed and optimized luminescence was achieved with the sample having the concentration x = 07 mol%. The lifetimes of the donor and acceptor and energy transfer from gadolinium to neodymium were obtained from the luminescence decay kinetics. The findings show that Nd-doped Gd2O3-modified glass materials have potential as NIR laser sources.

Luminescence characteristics of Sm3+-doped lithium barium gadolinium silicate glasses for Orange LED's.

Traditional melt-quenching technique is adopted for synthesis of Sm2O3 doped lithium barium gadolinium silicate (LBGS: Li2O-BaO-Gd2O3-SiO2) glasses. These glass samples are characterized by different spectroscopic techniques under ambient conditions. Density and molar volume of the present LBGS glass samples increase with increasing Sm3+ ion-concentration. JO intensity parameters Ωλ (where λ = 2, 4 and 6) are evaluated by using Judd-Ofelt theory and Ω4 > Ω2 > Ω6 trend is observed. Furthermore, these parameters are used to evaluate radiative properties like radiative transition probability, branching ratio, radiative lifetime and stimulated emission cross-section for state 4G5/2 of Sm3+ ion. The measured color coordinates for the title glass fall within orange region of CIE diagram. For the present LBGS glasses, the correlated color temperature values are less than warm. The lifetime for the 4G5/2 decreases from 2.468 to 0.566 ms when concentration increases from 0.1 to 2.0 mol% of Sm3+ ions. The analysis of non-exponential behavior of the decay profile through Inokuti-Hirayama model for S = 6 indicates that the energy transfer between Sm3+ ions is due to dipole-dipole interactions. Further energy transfer parameters (Q), critical distance (Ro, Å) and donor-acceptor interaction parameters (CDA x 10-40 cm6/s) of Sm3+ ions doped LBGS glasses were evaluated and compared to other glasses. From the evaluated results it is suggested that the present novelty of the work emphasizes on new matrix LBGS doped with Sm3+ ions showing increasing energy transfer rate with increasing in concentration of Sm2O3 content indicating these glasses are potential candidate for orange-light emitting device applications.

Energy transfer phenomenon of Gd3+ to excited ground state of Eu3+ ions in Li2O-BaO-Gd2O3-SiO2-Eu2O3 glasses.

Li2O-BaO-Gd2O3-SiO2 glasses with different concentration of Eu3+ ions were developed by the traditional melt quenching technique and characterized via FTIR, absorption, excitation, emission and CIE color coordinates analysis for visible red emission application. The FTIR shows strong band at position 740 cm-1 which is attributed to Si-O-Si symmetric stretching mode. Density and molar volume of LBGSEu glasses increases with Eu3+ ions concentration. The covalent nature of bond between the Eu3+ ions and surrounding ligands was confirmed from the bonding parameter (δ). From absorption spectra JO-parameters and oscillator strength are evaluated for LBGSEu6 glass. From JO-parameters, Eu3+ ions have asymmetric coordination environment and stronger covalency. The phonon line PSB (22,522 cm-1) confirm the phonon energy ≈971 cm-1, that corresponds to the energy of one phonon associated with maximum energy of the vibrational mode couple to Eu3+ ions. Under 275 nm and 393 nm excitation, intense red emission was observed at 613 nm, we observe efficient energy transfer phenomena from Gd3+ → Eu3+ in these glasses. Increasing trend of IR with increasing concentration of Eu2O3 indicates the asymmetric environment around Eu3+ ions in LBGS. Moreover, from JO analysis, LBGS glasses have high capability for red laser device with high lasing power and energy extraction ratio. The fluorescence lifetimes show decreasing trend in lifetime with increasing concentration of Eu2O3 is due to radiative transition. From CIE color coordinate, the CIE color coordinates of LBGSEu6 glass fall in reddish region close to orange region and can be useful for optical display devices.