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Eu3+-doped barium borate glasses are analysed for their optical and excitation power dependent luminescence properties. The glasses, doped with different concentrations of the lanthanide ion Eu3+, provide photoluminescence quantum efficiencies higher than 80% and, show a bright luminescence in the red spectral range, making them attractive for lighting applications. [ABSTRACT FROM AUTHOR]

The ratio between the network modifier Li2O and the network former B2O3 has a significant influence on the structural and optical properties of Dy3+-doped lithium borate glass. Differential scanning calorimetry shows that upon increasing the modifier-to-former ratio (Li2O-to-B2O3) in favour of Li2O, the glass transition temperature increases up to a maximum value of 502°C for the 1:3 sample, while the crystallization temperature decreases linearly from 653 to 534°C. Raman spectroscopy confirms the highest network connectivity for the glass with a modifier-to-former ratio of 1:3. Under ultraviolet excitation, Dy3+ shows emission lines in the visible spectral range, the most intense ones at 484 and 575 nm. The absolute photoluminescence quantum efficiency is best for the glass with a modifier-to-former ratio of 1:6. [ABSTRACT FROM AUTHOR]

Tb3+ and Eu3+ single-doped barium borate glass and ZBLAN glass are investigated for their photoluminescence (PL) and absolute PL quantum efficiency. In addition, both glass systems are characterized with respect to their color stability in the temperature range from 25 °C to 400 °C. The Tb3+ doped glass shows high color stability over the entire temperature range investigated, whereas the Eu3+ doped glass changes its color appearance with increasing temperature: Eu3+ in ZBLAN glass changes its color appearance from the orange to the red spectral range, whereas the color appearance in borate glass is shifted from the red to the orange-red spectral range. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The application of Mössbauer spectroscopy to luminescent materials is described. Many solids doped with europium are luminescent, i.e., when irradiated with light they emit light of a longer wavelength. These materials therefore have practical applications in tuning the light output of devices like light emitting diodes. The optical properties are very different for the two possible valence states Eu 2 + and Eu 3 + , the former producing ultraviolet/visible light that shifts from violet to red depending on the host and the latter red light, so it is important to have a knowledge of their behavior in a sample environment. Photoluminescence spectra cannot give a quantitative analysis of Eu 2 + and Eu 3 + ions. Mössbauer spectroscopy, however, is more powerful and gives a separate spectrum for each oxidation state enabling the relative amount present to be estimated. The oxidation state can be identified from its isomer shift which is between - 12 and - 15 mm/s for Eu 2 + compared to around 0 mm/s for Eu 3 + . Furthermore, within each oxidation state, there are changes depending on the ligands attached to the europium: the shift is more positive for increased covalency of the bonding ligand X, or Eu concentration, and decreases for increasing Eu⁻X bond length.