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Up-conversion luminescence spectra of Er 3+ ions in PbO–Ga 2 O 3 –GeO 2 and PbO–Ga 2 O 3 –SiO 2 glasses have been examined as a function of temperature in the 298–650 K range. The relative emission intensities of green bands corresponding to 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 transitions of Er 3+ were determined with temperature. Based on up-conversion luminescence spectra of Er 3+ , the fluorescence intensity ratio and temperature sensitivity for glasses based on PbO–Ga 2 O 3 –XO 2 (X = Ge, Si) were calculated. The maximum sensitivity is equal to 20.4 × 10 − 4 K − 1 at T = 620 K (X = Ge) and 26.4 × 10 − 4 K − 1 at T = 590 K (X = Si) suggesting potential application in optical sensor thermometry. [ABSTRACT FROM AUTHOR]

The glass structure, photoluminescence properties of Eu 3+ , Judd–Ofelt analysis, and near infrared emissions of Er 3+ at 1.5 μm in the oxyfluoride glasses and glass–ceramics of 1Eu 2 O 3 - or 1Er 2 O 3 -doped 50BaF 2 – x Al 2 O 3 –(50 − x )B 2 O 3 ( x = 0–25 mol%) were investigated. It was clarified on the ground of Raman scattering spectroscopy and F1s and O1s XPS measurements that the glass with no Al 2 O 3 (1Er 2 O 3 –50BaF 2 –50B 2 O 3 ) is composed of BO 3 , BO 2 F and BO 3 F units with F–Ba bonds. The glasses with 25Al 2 O 3 (1Er 2 O 3 –50BaF 2 –25Al 2 O 3 –25B 2 O 3 ) is mainly composed of BO 3− and Al(O,F) x units. Existence of non-bridging oxygen was not detected by O1s-XPS spectra. It was proposed that these structures are largely affected on crystallization behavior, e.g., the glass with no Al 2 O 3 forms BaF 2 and β -BaB 2 O 4 due to Ba–F bonds and the glass with 25Al 2 O 3 forms BaAlBO 3 F 2 because the glass structure composed of BO 3 and Al(O,F) units is similar to the BaAlBO 3 F 2 crystal structure. Judd–Ofelt parameters of Er 3+ and Eu 3+ in the glasses showed almost the same values in Ω 4 and Ω 6 for each glass, on the other hand Ω 2 decreased with addition of Al 2 O 3 . The emission spectra of Er 3+ at 1.5 μm in the glasses and glass–ceramics with BaAlBO 3 F 2 crystals showed broad peaks. It is proposed that oxyfluoride glasses and glass–ceramics based on the BaF 2 –Al 2 O 3 –B 2 O 3 system have a high potential for optical device applications such as broadband optical amplifiers. [ABSTRACT FROM AUTHOR]

Lead-free oxyfluoride borate glasses singly doped with Pr 3+ and Er 3+ were prepared and next investigated using absorption and luminescence spectroscopy. In the studied glass system, barium oxide was substituted by BaF 2 . Two luminescence bands of Pr 3+ located at visible spectral region are observed, which correspond to 3 P 0 – 3 H 4 (blue) and 1 D 2 – 3 H 4 (reddish orange) transitions, respectively. The luminescence bands due to 1 D 2 – 3 H 4 transition of Pr 3+ are shifted to shorter wavelengths, when BaO was substituted by BaF 2 . Near-infrared luminescence spectra of Er 3+ ions in lead-free borate glasses modified by BaF 2 correspond to 4 I 13/2 – 4 I 15/2 transition. Their spectral linewidths increase with increasing BaF 2 concentration. The changes in measured lifetimes of rare earth ions are well correlated with the bonding parameters calculated from the optical absorption spectra. [ABSTRACT FROM AUTHOR]

Abstract: Structural and optical properties of Eu3+ and Dy3+ ions in PbO–Ga2O3–XO2 (X=Te, Ge, Si) glasses have been examined using X-ray diffraction, FT-IR and luminescence spectroscopy. Several crystalline phases such as TeO2, PbTe3O7, PbO and PbO2 were identified in lead tellurite system using X-ray diffraction analysis, in contrast to PbO–Ga2O3–XO2 (X=Ge, Si) glass samples. Characteristic emission bands due to the 5D0 → 7F J (J =0–4) transitions of Eu3+ and the 4F9/2 → 6H J /2 (J =15, 13, 11) transitions of Dy3+ were registered. Two spectroscopic parameters, such as luminescence intensity ratios associated to 5D0 → 7F2 and 5D0 → 7F1 transitions of Eu3+ as well as 4F9/2 → 6H13/2 and 4F9/2 → 6H15/2 transitions of Dy3+, and luminescence lifetimes for excited states of rare earth ions were determined. The luminescence intensity ratios for Eu3+ and Dy3+ ions decrease, whereas 5D0 (Eu3+) and 4F9/2 (Dy3+) luminescence lifetime increases, when covalence between Ln3+ and O2− ions is reduced and the phonon energy of the host glass is increased in PbO–TeO2 →PbO–GeO2 →PbO–SiO2 direction. It was confirmed by FT-IR measurements. [Copyright &y& Elsevier]

Abstract: Transparent glass-ceramics were successfully prepared during controlled heat treatment of lead borate glasses. The PbF2 particles were dispersed into a borate glass matrix which was evidenced by X-ray diffraction analysis. The phase identification revealed that crystalline peaks can be related to the orthorhombic PbF2 phase. Green up-conversion luminescence due to the 4S3/2–4I15/2 transition of Er3+ ions was registered. In comparison to the precursor glass the luminescence intensity was considerably higher, whereas the luminescence linewidth slightly decreased in the studied oxyfluoride transparent glass-ceramics. It indicated that apart of the trivalent erbium was incorporated into the PbF2 crystalline phase. [Copyright &y& Elsevier]

Luminescence properties of olivine-type germanate phosphors with general formula Li 2 AGeO 4 :0.5Er3+ (A = Zn, Mg) have been studied. Olivine-type materials prepared via conventional solid-state reaction method were examined for down- and up-conversion luminescence processes. In the down-conversion process after 381 nm excitation, two strong green emission bands due to 2H 11/2 /4S 3/2 → 4I 15/2 transitions of Er3+ were registered, with a change in the intensity ratio depending on the ceramic matrix. Weak red emission bands related to 4F 9/2 → 4I 15/2 transition were also recorded. In contrast, luminescence bands behaved completely differently for the up-conversion process after infrared excitation at λ exc = 980 nm. Red emission bands were much more significant than green emission bands. These effects are stronger for Li 2 MgGeO 4 :0.5Er3+ than Li 2 ZnGeO 4 :0.5Er3+. In the red and green spectral range, slope values for both matrices Li 2 AGeO 4 :0.5Er3+ (A = Zn, Mg) confirmed two-photon process. • Phosphors Li 2 AGeO 4 :Er3+ (A = Zn, Mg) with olivine structure were studied. • Down/up conversion luminescence processes of Er3+ ions were examined. • Intensities of green/red emission bands depend strongly on the excitation wavelengths. • Two-photon up-conversion process in Li 2 AGeO 4 :Er3+ (A = Zn, Mg) was confirmed. [ABSTRACT FROM AUTHOR]

Abstract In this work, Eu3+-doped glass-ceramic materials containing LaF 3 nanocrystals (GC Eu3+:LaF 3) were fabricated by controlled heat-treatment of precursor xerogels synthesized via low-temperature sol-gel method. In order to characterize the thermal resistance of silica xerogels and to determine the crystallization temperature of LaF 3 phase the TG/DSC analysis was performed. The formation of LaF 3 nanocrystals in glass-ceramics was confirmed by X-ray diffraction measurements (XRD) and high-resolution transmission electron microscopy (HRTEM). In addition, the IR-ATR spectra were registered to identify the types of vibrational modes existing within prepared sol-gel hosts. The photoluminescence behavior of synthesized Eu3+-doped materials was characterized based on PLE (λ em = 611 nm) and PL spectra (λ exc = 393 nm) as well as luminescence decay analysis. The characteristic 5D 0 → 7F J (J = 0–4) intra-configurational transitions within 4f6 manifold of Eu3+ ions were registered in reddish-orange spectral range. In order to estimate the symmetry in local framework around Eu3+ ions the R/O-factor defined as I(5D 0 → 7F 2)/I(5D 0 → 7F 1) was calculated. The recorded decay curve for GC Eu3+:LaF 3 exhibits bi-exponential profile, what provides the distribution of Eu3+ ions between two local sites with different decay rates. Highlights • Eu3+-doped xerogels and glass-ceramics were prepared using sol-gel method. • LaF 3 nanocrystals doped with Eu3+ions were successfully identified. • The efficient photoluminescence in reddish-orange light area was detected. • The influence of vibrational modes on luminescence behavior of Eu3+ was observed. [ABSTRACT FROM AUTHOR]

Abstract Fully amorphous rare earth co-doped barium gallo-germanate glasses were synthesized using the traditional melt quenching-technique. The glass systems were doped with selected pairs of rare earths Dy3+/Ce3+ and Dy3+/Tm3+ ions. To study the spectroscopic properties of gallo-germanate glasses co-doped with Dy3+ and Ln3+ (Ln = Ce, Tm) ions, the luminescence spectra and luminescence decay curves were recorded. It was observed that luminescence bands corresponding to characteristic transitions of Ln3+ (Ln = Ce, Tm) and dysprosium ions are present in the emission spectra measured under direct excitation of Ln3+. The experimental results indicate that energy transfer between dysprosium and cerium/thulium ions is effective. From the emission spectra, the Commission Internationale de I'Eclairage (CIE) chromaticity coordinates (x, y) were calculated in relation to the potential application of gallo-germanate glasses for white LEDs. It has been proved that our glass systems exhibit white emission originating from the simultaneous generation of several bands of Dy3+, Ce3+/Tm3+ under the UV-visible light excitation. Highlights • The rare earth co-doped barium gallo-germanate glasses were synthesized. • The luminescence spectra and luminescence decay curves were registered. • The energy transfer between dysprosium and cerium/thulium ions was examined. • The glass systems exhibit white emission under the UV-visible light excitation. [ABSTRACT FROM AUTHOR]

Fully amorphous lead borate glasses triply doped with Dy 3+ /Tb 3+ /Eu 3+ were synthesized and next studied using optical spectroscopy. The characteristic luminescence bands originating to electronic transitions of Dy 3+ /Tb 3+/ Eu 3+ ions were observed under direct excitation of Dy 3+ . Moreover, the influence of concentration of rare earth ions on spectroscopic properties of lead borate glasses was examined. The obtained experimental results indicate that energy transfer between these rare earth ions is possible. From the emission spectra, the Commission Internationale de I'Eclairage (CIE) chromaticity coordinates (x, y) are calculated in relation to potential application lead borate glasses for white light emitting devices. It has been proved that our glass systems exhibit warm white emission originating from the simultaneous generation of several bands of Dy 3+ , Tb 3+ , Eu 3+ under the UV–visible light excitation. [ABSTRACT FROM AUTHOR]

Series of Eu 3+ -doped lead-free germanate and borate glasses were synthesized. The MO glass modifiers (M = Ca, Sr or Ba) were partially or totally substituted by MF 2 in chemical composition. In contrast to samples modified by CaO/CaF 2 or SrO/SrF 2 , the germanate glass samples containing BaO and/or BaF 2 are fully amorphous, while the lead-free borate glasses are fully amorphous, independently from glass modifiers. Effect of glass modifiers on spectroscopic properties of Eu 3+ were systematically investigated. For that reason, excitation and emission spectra of Eu 3+ ions in examined systems were registered. Based on the emission spectra, ratio of integrated luminescence intensity of the 5 D 0 → 7 F 2 transition to that of the 5 D 0 → 7 F 1 transition (R factor) was calculated. Moreover, the luminescence decay curves were collected and the luminescence lifetimes of the 5 D 0 excited state of Eu 3+ ions were determined in function of MF 2 concentration. [ABSTRACT FROM AUTHOR]

New multicomponent europium-doped lead phosphate based glasses with various PbO:P 2 O 5 molar ratios were prepared and next studied using optical spectroscopy. Based on excitation and luminescence spectra measurements, some spectroscopic parameters like the phonon energy of the glass host and the fluorescence intensity ratio R of the 5 D 0 → 7 F 2 to 5 D 0 → 7 F 1 transition of Eu 3+ ions were determined. Luminescence lifetimes ( τ m ) for the 5 D 0 state of Eu 3+ ions were also evaluated. Optical properties of Eu 3+ ions have been investigated in lead phosphate based systems, in which PbO:P 2 O 5 molar ratio were changed from 1:5 to 5:1 in glass composition. The value of the phonon energy of the host decreases with increasing PbO concentration. In addition, the spectral lines are shifted toward higher wavelengths. Non-monotonic dependence of fluorescence intensity ratio R (Eu 3+ ) upon PbO:P 2 O 5 content has been observed. Influence of PbO:P 2 O 5 molar ratio on spectroscopic parameters for Eu 3+ are presented and discussed. [ABSTRACT FROM AUTHOR]