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Temperature-dependent up-conversion luminescence spectra of Er 3+ in lead-free germanate glass have been examined under 800 nm and 980 nm diode laser excitation. Green up-conversion luminescence spectra measured in the 500–580 nm ranges correspond to transitions originating from thermally coupled 2 H 11/2 and 4 S 3/2 levels to 4 I 15/2 ground level of Er 3+ . The relative emission band intensities of 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 transitions of Er 3+ are changed with temperature. The rate of fluorescence intensity ratio varying with temperature was calculated for glass sample excited at 800 nm and 980 nm, respectively. The maximum temperature sensitivity is nearly 20% higher for glass sample pumped at 980 nm than 800 nm. [ABSTRACT FROM AUTHOR]

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]

Spectroscopic properties of Er 3+ ions in lead-free oxyfluoride germanate glasses were studied. The absorption and luminescence spectra of Er 3+ ions were examined for glass samples with low and high BaF 2 content. From absorption spectra the bonding parameter was calculated and its value is reduced with increasing BaF 2 content. The maximum of absorption peak due to 4 I 15/2 − 2 H 11/2 hypersensitive transition is shifted to shorter wavelengths (blue shift) with increasing BaF 2 content. Luminescence spectra and their decays corresponding to main 4 I 13/2 − 4 I 15/2 laser transition of Er 3+ are also presented and discussed. Quite long-lived near-infrared luminescence of Er 3+ is observed for lead-free glass samples with low BaF 2 concentration. [ABSTRACT FROM AUTHOR]

Abstract: Luminescence of lead bismuthate glasses PbO-Bi2O3-Ga2O3 containing Dy3+ ions has been studied. Two overlapping luminescence bands corresponding to 3P1–1S0 transition of Bi3+ and 4F9/2 –6H13/2 transition of Dy3+ were detected under 480nm excitation. Comparison of luminescence features for the system under study to those reported for dysprosium-doped lead borate glass PbO-B2O3-Ga2O3 indicates that the luminescence of Dy3+ is efficiently quenched by Bi3+ ions. Analysis of luminescence dynamics implies that the excitation energy transfer from Dy3+ to Bi3+ is nonradiative. The theoretical calculations using Inokuti–Hirayama model confirm strong luminescence of Dy3+ ions in lead bismuthate glasses. [Copyright &y& Elsevier]

Abstract: Selected heavy metal glasses containing Yb3+ and Er3+ ions have been studied. Near-infrared luminescence spectra at 1.53μm and up-conversion spectra of Er3+ ions were registered under excitation of Yb3+ ions by 975nm diode laser line. The luminescence bands correspond to 4I13/2–4I15/2 (NIR), 4S3/2–4I15/2 (green) and 4F9/2–4I15/2 (red) transitions of Er3+, respectively. The optical transitions of rare earth ions have been examined as a function of glass host. The unusual large spectral linewidth nearly close to 110nm for 4I13/2–4I15/2 transition of Er3+ ions in Yb–Er co-doped lead borate glass was obtained, whereas long-lived NIR luminescence at 1.53μm was detected in lead germanate glass. The NIR luminescence and up-conversion phenomena strongly depend on stretching vibrations of glass host, which was confirmed by FT-IR spectroscopy. [Copyright &y& Elsevier]

Abstract: Ln-doped oxychloride lead borate glasses were studied using luminescence spectroscopy. Rare earth ions were limited to trivalent Pr3+, Tm3+, Eu3+ and Er3+. Luminescence spectra were registered, which correspond to 3P0–3H4 and 1D2–3H4 transitions of Pr3+, 1G4–3H5 and 1G4–3F4 transitions of Tm3+, 5D0–7F J (J=0, 1, 2, 3, 4) transitions of Eu3+ and 4S3/2,2H11/2–4I15/2 and 4I13/2–4I15/2 transitions of Er3+. Luminescence decays from the excited states of Ln3+ ions were analyzed in detail. The experimental results indicate that relatively high phonon energy of the host gives important contribution to the excited state relaxation of rare earth ions. [Copyright &y& Elsevier]

Abstract: The spectroscopic and laser properties of Nd3+ and Dy3+ ions in lead borate glass were studied. Luminescence spectra recorded in the near-infrared and visible ranges correspond to 4F3/2–4I J /2 (J=9, 11, 13) transitions of Nd3+ and 4F9/2–6H J /2 (J=11, 13, 15) transitions of Dy3+, respectively. Luminescence decay curves were analyzed as a function of activator concentration. Luminescence quenching is observed, which is due to Ln–Ln interaction increasing. Several spectroscopic parameters relevant to laser potential of Ln3+ ions (Ln=Nd, Dy) in lead borate glass were determined. The relatively large values of the quantum efficiency and the room-temperature emission cross-section for the 4F3/2–4I11/2 transition of Nd3+ at 1061nm and the 4F9/2–6H13/2 transition of Dy3+ at 573nm imply that Ln-doped lead borate glasses can be considered as promising solid-state materials for laser applications. [Copyright &y& Elsevier]

Fluoroindate glasses co-doped with Pr3+/Er3+ ions were synthesized and their near-infrared luminescence properties have been examined under selective excitation wavelengths. For the Pr3+/Er3+ co-doped glass samples several radiative and nonradiative relaxation channels and their mechanisms are proposed under direct excitation of Pr3+ and/or Er3+. The energy transfer processes between Pr3+ and Er3+ ions in fluoroindate glasses were identified. In particular, broadband near-infrared luminescence (FWHM = 278 nm) associated to the 1G4 → 3H5 (Pr3+), 1D2 → 1G4 (Pr3+) and 4I13/2 → 4I15/2 (Er3+) transitions of rare earth ions in fluoroindate glass is successfully observed under direct excitation at 483 nm. Near-infrared luminescence spectra and their decays for glass samples co-doped with Pr3+/Er3+ are compared to the experimental results obtained for fluoroindate glasses singly doped with rare earth ions. [ABSTRACT FROM AUTHOR]

Novel multicomponent titanate-germanate glasses singly doped with transition metal (Cr3+) and rare earth ions (Eu3+) were synthesized and the glass transition temperatures and thermal stability parameters were determined using DSC measurements. X-ray diffraction analysis confirmed fully amorphous nature of the received samples. Their structural and optical properties were compared with germanate glasses without TiO2. Correlation between local structure and optical properties in titanate-germanate glasses is well evidenced by FT-IR, Raman, EPR, and luminescence spectroscopy. In particular, luminescence spectra and their decays are examined for glass samples, where GeO2 was partially substituted by TiO2. [ABSTRACT FROM AUTHOR]

Glass-ceramic is semi-novel material with many applications, but it is still problematic in obtaining fibers. This paper aims to develop a new glass-ceramic material that is a compromise between crystallization, thermal stability, and optical properties required for optical fiber technology. This compromise is made possible by an alternative method with a controlled crystallization process and a suitable choice of the chemical composition of the core material. In this way, the annealing process is eliminated, and the core material adopts a glass-ceramic character with high transparency directly in the drawing process. In the experiment, low phonon antimony-germanate-silicate glass (SGS) doped with Eu3+ ions and different concentrations of P2O5 were fabricated. The glass material crystallized during the cooling process under conditions similar to the drawing processes'. Thermal stability (DSC), X-ray photo analysis (XRD), and spectroscopic were measured. Eu3+ ions were used as spectral probes to determine the effect of P2O5 on the asymmetry ratio for the selected transitions (5D0 → 7F1 and 5D0 → 7F2). From the measurements, it was observed that the material produced exhibited amorphous or glass-ceramic properties, strongly dependent on the nucleator concentration. In addition, the conducted study confirmed that europium ions co-form the EuPO4 structure during the cooling process from 730 °C to room temperature. Moreover, the asymmetry ratio was changed from over 4 to under 1. The result obtained confirms that the developed material has properties typical of transparent glass-ceramic while maintaining high thermal stability, which will enable the fabrication of fibers with the glass-ceramic core. [ABSTRACT FROM AUTHOR]

Abstract: Effects of PbF2 concentration on spectroscopic properties of Eu3+ and Dy3+ ions in lead borate glasses have been studied. The samples where PbO was partially or totally substituted by PbF2 were examined using DSC, FT-IR, Raman, absorption and luminescence spectroscopies. Luminescence spectra and their decays were analyzed in detail. Especially, the luminescence intensity ratios R (Eu3+) and Y/B (Dy3+) as well as luminescence lifetimes of 5D0 (Eu3+) and 4F9/2 (Dy3+) excited states of rare earth ions have been determined. [Copyright &y& Elsevier]

• GeO 2 -TiO 2 -BaO-BaF 2 -Ga 2 O 3 system doped with Er3+, Tm3+, Ho3+ were synthesized. • The extremely low IR absorption coefficients were achieved. • Enhanced emission at 1.5 µm, 1.8µm and 2.0 µm by introducing BaF 2 in the composition was observed. • The luminescence lifetime significantly increased in the function BaF 2. • Optimal BaF 2 content in titanate-germanate glass was evaluated. A novel TiO 2 -GeO 2 -BaO-BaF 2 -Ga 2 O 3 glasses doped with rare-earth were synthesized, and the impact of the substitution of BaF 2 for BaO on properties has been investigated by luminescence spectroscopy. The IR absorption coefficient is extremely low, which is attractive for optical fibers emitting NIR radiation. Near-IR luminescence associated to the Er3+:4I 13/2 → 4I 15/2 (FWHM = 108 nm), Tm3+:3F 4 → 3H 6 (FWHM = 244 nm) and Ho3+:5I 7 → 5I 8 (FWHM = 179 nm) transitions are enhanced in the presence of BaF 2. Luminescence lifetimes increase with increasing content of BaF 2 in the glass composition. Fabricated optical materials with relatively high BaF 2 content represent a good starting point for further investigations in the field of glass technology and modern photonics. [ABSTRACT FROM AUTHOR]

Lead phosphate glasses singly-doped with selected Ln3+ ions (Ln = Pr, Tm) were prepared by traditional melt-quenching method. The effect of concentration of optical active dopants in glass composition on spectroscopic properties of lead phosphate glasses were systematically investigated based on excitation, visible and near-infrared emission spectra as well as luminescence decay analysis. It was found that the luminescence intensity decreases with increasing content of Pr3+ and Tm3+ ions due to the concentration quenching. Also, the luminescence lifetimes of 1D 2 , 1G 4 (Pr3+) and 1D 2 , 3H 4 (Tm3+) states decrease with increasing concentration of both ions. Based on luminescence decay analysis and calculations using theoretical Inokuti-Hirayama model it was confirmed that non-radiative processes like cross-relaxation among the donor systems are dominate and influence direct donor-acceptor energy transfer in lead phosphate glasses. Moreover, the obtained results suggest clearly lower self-quenching emission in lead phosphate glasses doped with Pr3+ than Tm3+ ions. • Lead phosphate glasses singly doped with Pr3+ and Tm3+ were obtained. • Luminescence spectra of Ln3+ (Ln = Pr and Tm) and their decays were examined. • The quenching of the visible and near-infrared luminescence were observed when concentration of Pr3+ and Tm3+ ions increase. • The luminescence lifetimes decrease with increasing concentration of Ln3+ ions. • The luminescence quenching via non-radiative energy transfer processes was explained by theoretical Inokuti-Hirayama model. [ABSTRACT FROM AUTHOR]

Abstract: Visible luminescence of Dy3+ ions in oxyhalide lead borate glasses was examined. Luminescence spectra show two intense bands at 480nm and 573nm due to 4F9/2 → 6H15/2 (blue) and 4F9/2 → 6H13/2 (yellow) transitions of Dy3+. Luminescence decays from 4F9/2 state and yellow-to-blue luminescence intensity ratios (Y/B) were analysed with PbX2 (X=F, Cl) content. An introduction of PbX2 to the borate glass results in the increasing of 4F9/2 lifetime and the decreasing of yellow-to-blue luminescence intensity ratio, which is due to reduction of covalency between Dy3+ and O2−/X− ions. [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]

Series of lead-free borate glasses with different oxide modifiers and lanthanide ions were prepared. The effect of oxide modifiers MO (M = Ca, Sr, Ba) on spectroscopic properties of trivalent Ln 3+ (Ln = Eu, Er, Pr) were systematically investigated. Especially, the luminescence spectra of Ln 3+ -doped lead-free borate glasses are presented and discussed in relation to the impact of selective components (CaO, SrO and BaO). Several spectroscopic parameters, such as the fluorescence intensity ratio R/O (Eu 3+ ) and measured luminescence lifetimes for the 5 D 0 (Eu 3+ ), 4 I 13/2 (Er 3+ ) and 1 D 2 (Pr 3+ ) excited states of lanthanide ions were analyzed in details. The research proved that spectroscopic properties of trivalent Ln 3+ depend significantly on kind of presence oxide modifiers MO (M = Ca, Sr, Ba) in glass host matrices. [ABSTRACT FROM AUTHOR]

Rare-earth-doped oxyfluoride germanate and borate glasses were synthesized and next studied using spectroscopic methods. Influence of fluoride modifier on luminescence properties of rare earths in different glass hosts was examined. The excitation and emission spectra of Pr3+ and Er3+ ions in the studied glasses were registered. The emission spectra of Pr3+ ions in germanate and borate glasses are quite different and depend strongly on the glass host. In samples doped with Er3+ ions emission bands located around 1530 nm corresponding to the main 4I13/2→4I15/2 laser transition were registered, independently of the glass host. Quite long-lived near-infrared luminescence of Er3+ ions was observed for germanate glasses with low BaF2 content, while in borate glass systems influence of barium fluoride on luminescence lifetimes is not so evident. The Judd-Ofelt calculations were used in order to determine quantum efficiencies of excited states of rare-earth ions in germanate and borate glasses. [ABSTRACT FROM AUTHOR]

In this research, the effects of fluoride ions concentration on luminescence properties of Eu 3+ :PbF 2 nanocrystals in silicate sol–gel materials have been investigated. Optical and structural properties of Eu 3+ :PbF 2 nanocrystals have been examined using X-ray diffraction analysis (XRD) and luminescence spectroscopy. Formation of the cubic β-PbF 2 nanocrystalline phase was confirmed. The crystal size was estimated using Scherrer's equation and Williamson-Hall formula. The optical behavior of Eu 3+ ions in studied materials is strongly dependent on amount of incorporated fluorides in the host lattice and the optimal concentration about 3.0 mass. % give the more intense emission of Eu 3+ . The luminescence spectra showed the characteristic orange-red emission due to the 5 D 0 → 7 F 1 and 5 D 0 → 7 F 2 electron transitions, respectively. The luminescence intensity ratio R (I( 5 D 0 → 7 F 2 )/I( 5 D 0 → 7 F 1 )) and luminescence lifetimes for the 5 D 0 excited state of Eu 3+ ions were determined for each sample before and after heat treatment process. Obtained results indicate the partially incorporation of Eu 3+ ions into β-PbF 2 nanocrystalline phase during ceramization process. [ABSTRACT FROM AUTHOR]

Eu 3+ /Gd 3+ co-doped silicate sol–gel powders have been successfully obtained. The effect of high concentration of gadolinium ions on visible emission of europium ions in prepared materials has been studied under different excitation wavelengths. Spectroscopic properties of Eu 3+ and Gd 3+ ions in prepared powders were determined based on excitation and emission measurements as well as luminescence decay analysis. In the visible spectral range the observed emission bands correspond to transitions of trivalent Eu 3+ and Gd 3+ ions. The changes of excitation mechanism of optically active dopants significantly affect the increase of luminescence intensities. The luminescence lifetime for the 5 D 0 level of Eu 3+ ions in examined samples upon excitation at λ exc =273 nm ( 8 S 7/2 → 6 I J transition of Gd 3+ ) is about 12 times longer in comparison to excitation at λ exc =393 nm ( 7 F 0 → 5 L 6 transition of Eu 3+ ). The luminescence intensity coefficient R (Eu 3+ ) was also calculated, and it was found that ratio of the intensity of red to orange emission depends on the excitation wavelength. Based on determined spectroscopic parameters the energy transfer process from Gd 3+ to Eu 3+ ions 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]

Highlights: [•] Tb-doped heavy metal glasses were studied as a function of glass composition. [•] Excitation and luminescence spectra of Tb ions in heavy metal glasses were examined. [•] Luminescence intensity ratios (G/B) and measured lifetimes of Tb were determined. [•] Correlation between G/B factor, measured lifetimes and energy phonon was proposed. [ABSTRACT FROM AUTHOR]

An investigation of the structural and luminescent properties of the transparent germanate glass-ceramics co-doped with Ni2+/Er3+ for near-infrared optical fiber applications was presented. Modification of germanate glasses with 10–20 ZnO (mol.%) was focused to propose the additional heat treatment process controlled at 650 °C to obtain transparent glass-ceramics. The formation of 11 nm ZnGa2O4 nanocrystals was confirmed by the X-ray diffraction (XRD) method. It followed the glass network changes analyzed in detail (MIR—Mid Infrared spectroscopy) with an increasing heating time of precursor glass. The broadband 1000–1650 nm luminescence (λexc = 808 nm) was obtained as a result of Ni2+: 3T2(3F) → 3A2(3F) octahedral Ni2+ ions and Er3+: 4I13/2 → 4I15/2 radiative transitions and energy transfer from Ni2+ to Er3+ with the efficiency of 19%. Elaborated glass–nanocrystalline material is a very promising candidate for use as a core of broadband luminescence optical fibers. [ABSTRACT FROM AUTHOR]

In this work, the series of Tb3+/Eu3+ co-doped xerogels and derivative glass-ceramics containing CaF2 nanocrystals were prepared and characterized. The in situ formation of fluoride crystals was verified by an X-ray diffraction technique (XRD) and transmission electron microscopy (TEM). The studies of the Tb3+/Eu3+ energy transfer (ET) process were performed based on excitation and emission spectra along with luminescence decay analysis. According to emission spectra recorded under near-ultraviolet (NUV) excitation (351 nm, 7F6 → 5L9 transition of Tb3+), the mutual coexistence of the 5D4 → 7FJ (J = 6–3) (Tb3+) and the 5D0 → 7FJ (J = 0–4) (Eu3+) luminescence bands was clearly observed. The co-doping also resulted in gradual shortening of a lifetime from the 5D4 state of Tb3+ ions, and the ET efficiencies were varied from ηET = 11.9% (Tb3+:Eu3+ = 1:0.5) to ηET = 22.9% (Tb3+:Eu3+ = 1:2) for xerogels, and from ηET = 25.7% (Tb3+:Eu3+ = 1:0.5) up to ηET = 67.4% (Tb3+:Eu3+ = 1:2) for glass-ceramics. Performed decay analysis from the 5D0 (Eu3+) and the 5D4 (Tb3+) state revealed a correlation with the change in Tb3+–Eu3+ and Eu3+–Eu3+ interionic distances resulting from both the variable Tb3+:Eu3+ molar ratio and their partial segregation in CaF2 nanophase. [ABSTRACT FROM AUTHOR]

In this work, we performed a systematic analysis of the impact of selected chemical reagents used in sol-gel synthesis (i.e., N,N-dimethylformamide) and different catalyst agents (i.e., CH3COOH, HNO3) on the formation and luminescence of Eu3+-doped SiO2–LaF3 nano-glass–ceramics. Due to the characteristic nature of intra-configurational electronic transitions of Eu3+ ions within the 4f6 manifold (5D0 → 7FJ, J = 0–4), they are frequently used as a spectral probe. Thus, the changes in the photoluminescence profile of Eu3+ ions could identify the general tendency of rare earth materials to segregate inside low-phonon energy fluoride nanocrystals, which allows us to assess their application potential in optoelectronics. Fabricated sol-gel materials, from sols to gels and xerogels to nano-glass–ceramics, were examined using several experimental techniques: X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR), and luminescence measurements. It was found that the distribution of Eu3+ ions between the amorphous silicate sol-gel host and LaF3 nanocrystals is strictly dependent on the initial composition of the obtained sols, and the lack of N,N-dimethylformamide significantly promotes the segregation of Eu3+ ions inside LaF3 nanocrystals. As a result, we detected long-lived luminescence from the 5D0 excited state equal to 6.21 ms, which predisposes the obtained glass–ceramic material for use as an optical element in reddish-orange emitting devices. [ABSTRACT FROM AUTHOR]

• Glass-ceramics containing PbF 2 nanocrystals with 23.7 nm diameter were fabricated. • An incorporation of Eu3+/Tb3+ ions into PbF 2 nanocrystals were successfully observed. • A long-lived luminescence of Eu3+ ions was detected for glass-ceramics. • Tb3+→ Eu3+ energy transfer process in β-PbF 2 :Eu3+/Tb3+ was confirmed. In this work, the transparent glass-ceramics with PbF 2 nanocrystals doubly-doped with Eu3+ and Tb3+ ions were obtained by low-temperature sol–gel method. Thermal and structural properties were examined using thermogravimetric analysis (TG), differential scanning calorimetry (DSC) as well as IR-ATR spectroscopy. The formation of β-PbF 2 nanocrystals was confirmed by XRD results. The optical properties were studied based on excitation and emission spectra and luminescence decay analysis. Upon direct excitation of Eu3+ ions at 393 nm, only the characteristic transitions from the 5D 0 state of Eu3 were observed, but upon excitation of Tb3+ ions at 351 nm the characteristic transitions of Tb3+ and Eu3+ were registered, and emission of Eu3+ is impressively long-lived (7.43 ms) in comparison to that one obtained under 393 nm excitation. It proofs that energy transfer Tb3+ → Eu3+ occurs. Obtained luminescence spectra and double-exponential character of lifetimes indicated the successful migration of dopants into low phonon energy PbF 2 nanocrystal phase. [ABSTRACT FROM AUTHOR]