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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]

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]

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]