Fluorescence properties of Eu3+ ions doped borate and fluoroborate glasses containing lithium, zinc and lead

Transition Metals (Cr3+) and Lanthanides (Eu3+) in Inorganic Glasses with Extremely Different Glass-Formers B2O3 and GeO2

Glasses containing two different network-forming components and doped with optically active ions exhibit interesting properties. In this work, glass systems based on germanium dioxide and boron trioxide singly doped with lanthanides (Eu³⁺) and transition metals (Cr³⁺) ions are research subjects. Optical spectroscopy was the major research tool used to record excitation and emission spectra in a wide spectral range for studied systems. The emitted radiation of glasses doped with Cr³⁺ ions is dominated by broadband luminescence centered at 770 nm and 1050 nm (⁴T₂ → ⁴A₂). Interestingly, the increase of concentration of one of the oxides contributed to the detectable changes of the R-line (²E → ⁴A₂) of Cr³⁺ ions. Moreover, EPR spectroscopy confirmed the paramagnetic properties of the obtained glasses. The influence of molar ratio GeO₂:B₂O₃ on spectroscopic properties for Eu³⁺ ions is discussed. The intensity of luminescence bands due to transitions of trivalent europium ions as well as the ratio R/O decrease with the increase of B₂O₃. On the other hand, the increase in concentration B₂O₃ influences the increasing tendency of luminescence lifetimes for the ⁵D₀ state of Eu³⁺ ions. The results will contribute to a better understanding of the role of the glass host and thus the prospects for new optical materials.

From Structure to Luminescent Properties of B2O3-Bi2O3-SrF2 Glass and Glass-Ceramics Doped with Eu3+ Ions

Glass-ceramics with the composition B₂O₃-Bi₂O₃-SrF₂ were synthesized by the conventional melt-quenching technique and subsequent crystallization of the parental glasses. The temperature at which the ceramization was carried out was selected based on differential scanning calorimetry (DSC) analysis. The structure of the studied materials and the formation of SrF₂ nanocrystals were confirmed by the Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. It was found that the amount of strontium fluoride introduced into the parental borate-bismuth glass has a significant impact on the growth of SrF₂ nanocrystals. In particular, the influence of the crystalline SrF₂ phase on luminescence intensity and kinetics was studied using Eu₂O₃-doped samples. An increase in luminescence intensity was observed in the samples in which SrF₂ nanocrystals were formed. This is most likely related to the fact that some of the Eu³⁺ ions were (after annealing of the glass) located in the crystalline structure of strontium fluoride. This was confirmed both by the luminescence lifetime obtained based on the luminescence decay curves and the calculated Judd–Ofelt parameters, Ω₂ and Ω₄. The results achieved confirm that the glasses and glass-ceramics described in this work could be considered as a new phosphor for light-emitting diodes (LEDs).

Controllable luminescence and efficient energy transfer investigation of a novel white light emission phosphor Ca19Na2Mg(PO4)14: Dy3+, Tm3+ with high thermal stability

White light emission phosphors are widely researched for application in lighting and display fields. However, the poor thermal stability is a real problem for the known single-phased white phosphors, which limits their further application. In this paper, Ca₁₉Na₂Mg(PO₄)₁₄: xDy³⁺, yTm³⁺ (CNMP, 0 ≤ x ≤ 0.06, y = 0, 0.01) phosphors with adjustable emission and good thermal stability are synthesized. The X-ray diffraction and X-ray energy dispersive spectrometer measurement distinctly confirm the successful synthesis of CNMP: xDy³⁺, yTm³⁺ (CNMP, 0 ≤ x ≤ 0.06, y = 0, 0.01). The photoluminescence results reveal that CNMP: Dy³⁺ shows characteristic excitation peaks in the range of 350-450 nm, and mainly exhibits strong yellow emission around 575 nm ascribed to the ⁴F_9/2-⁶H_13/2 transitions of Dy³⁺. To compensate the deficiency of blue light emission of CNMP: Dy³⁺, the trivalent Tm³⁺ ion is co-doped owing to its characteristic blue emission at 450 nm due to its ¹D₂-³F₄ transitions. Therefore, the emission of CNMP: Dy³⁺, Tm³⁺ can be tuned from blue light region with CIE coordinates of (0.1649, 0.0387) to white light region with CIE coordinates of (0.3001, 0.3003) and finally move to yellow light region with CIE coordinates of (0.3732, 0.4493) through adjusting the doping ratio of Dy³⁺/Tm³⁺. The energy transfer efficiency and the energy transfer mechanism from Tm³⁺ to Dy³⁺ are further investigated. Moreover, CNMP: Dy³⁺, Tm³⁺ exhibites a high thermal stability and the emission intensity still keeps 84% of the initial intensity of Dy³⁺ at 230 °C. These outstanding properties show that Ca₁₉Na₂Mg(PO₄)₁₄: Dy³⁺, Tm³⁺ have great advantages and potentiality for applying in solid state lighting.

Phonon Sideband Analysis and Near-Infrared Emission in Heavy Metal Oxide Glasses

In this work, spectroscopic properties of europium and erbium ions in heavy metal oxide glasses have been studied. The phonon energy of the glass host was determined based on Eu³⁺ excitation spectra measurements. Near-IR emission spectra at 1550 nm related to ⁴I_13/2 → ⁴I_15/2 transition of erbium in heavy metal glasses were examined with special regards to luminescence bandwidth and measured lifetime. In particular, correlation between phonon energy and the measured lifetime ⁴I_13/2 (Er³⁺) was proposed. The luminescence lifetime for the ⁴I_13/2 upper laser state of erbium decreases with increasing phonon energy in glass matrices. Completely different results were obtained glass samples with europium ions, where the ⁵D₀ lifetime increases with increasing phonon energy. Our investigations suggest that the values of measured ⁵D₀ lifetime equal to radiative lifetimes for all heavy metal oxide glasses.

Lead Borate Glasses and Glass-Ceramics Singly Doped with Dy3+ for White LEDs

In this paper, some series of lead borate glasses and glass ceramics singly doped with Dy³⁺ ions were prepared and then studied using spectroscopic techniques. Our research includes mainly studies of the luminescence properties of received materials for white light. The luminescence bands associated with the characteristic ⁴F_9/2→⁶H_15/2 (blue), ⁴F_9/2→⁶H_13/2 (yellow) and ⁴F_9/2→⁶H_11/2 (red) transitions of trivalent dysprosium in lead borate systems are well observed. In particular, the Commission Internationale de I’Eclairage (CIE) chromaticity coordinates (x, y) were calculated in relation to potential applications for white light-emitting diodes (W-LEDs). Their values depend on the relative B₂O₃/PbO ratios and PbX₂ contents (where X = Cl, F, Br) in glass composition. For glass-ceramics, the chromaticity coordinates are changed significantly under different excitation wavelengths.

Europium-Doped Tellurite Glasses: The Eu2+ Emission in Tellurite, Adjusting Eu2+ and Eu3+ Emissions toward White Light Emission

Europium-doped magnesium tellurite glasses were prepared using melt quenching techniques and attenuated total reflection (ATR) spectroscopy was used to study the glass structure. The glass transition temperature increased with increasing MgO content. Eu²⁺ and Eu³⁺ emissions were studied using photoluminescence spectroscopy (PL). The broad emission of Eu²⁺ ions centered at approximately 485 nm was found to decrease in intensity with increasing MgO content, while the Eu³⁺ emission was enhanced. The Eu³⁺ emission lay within the red orange range and its decay time was found to increase with increasing MgO content. Different excitation wavelengths were used to adjust Eu²⁺ to Eu³⁺ emissions to reach white light emission. The white light emission was obtained for the sample with the lowest MgO content under excitation in the near-UV range.

Spectroscopy and energy transfer in lead borate glasses doubly doped with Dy(3)(+)-Tb(3+) and Tb(3)(+)-Eu(3+) ions

Lead borate glasses doubly doped with Dy(3)(+)-Tb(3+) and Tb(3+)-Eu(3+) were investigated using optical spectroscopy. Luminescence spectra of rare earths were detected under various excitation wavelengths. The main green emission band due to (5)D4→(7)F5 transition of Tb(3+) is observed under excitation of Dy(3+), whereas the main red emission band related to (5)D0→(7)F2 transition of Eu(3+) is successfully observed under direct excitation of Tb(3+). In both cases, the energy transfer processes from Dy(3+) to Tb(3+) and from Tb(3+) to Eu(3+) in lead borate glasses occur through a nonradiative processes with efficiencies up to 16% and 18%, respectively. The presence of energy transfer process was also confirmed by excitation spectra measurements.

Optical properties of Eu³+ ions in phosphate glasses

Eu(3+)-doped phosphate (P(2)O(5)+K(2)O+SrO+Al(2)O(3)+Eu(2)O(3)) glasses with varying Eu(2)O(3) concentration have been prepared by standard melt quenching technique and are characterized through various spectroscopic techniques at room temperature. Luminescence spectra of these glasses exhibit the characteristic emission of Eu(3+) ion with an intense and most prominent red emission attributed to (5)D(0)→(7)F(2) transition. Crystal-field analysis has been carried out to estimate the local symmetry in the vicinity of Eu(3+) ions. Judd-Ofelt parameters have been evaluated from the luminescence intensity ratios of (5)D(0)→(7)F(J) (J=2, 4 and 6) to (5)D(0)→(7)F(1) transitions as well as absorption spectrum under different constraints. Decay rates for the (5)D(0) level of Eu(3+) ions have been recorded by monitoring the emission at around 609 nm corresponding to (5)D(0)→(7)F(2) transition. The experimental lifetime for the (5)D(0) level in title glasses is independent of Eu(3+) ion concentration.

Rare earth-doped lead borate glasses and transparent glass-ceramics: structure-property relationship

Correlation between structure and optical properties of rare earth ions in lead borate glasses and glass-ceramics was evidenced by X-ray-diffraction, Raman, FT-IR and luminescence spectroscopy. The rare earths were limited to Eu(3+) and Er(3+) ions. The observed BO(3)↔BO(4) conversion strongly depends on the relative PbO/B(2)O(3) ratios in glass composition, giving important contribution to the luminescence intensities associated to (5)D(0)-(7)F(2) and (5)D(0)-(7)F(1) transitions of Eu(3+). The near-infrared luminescence and up-conversion spectra for Er(3+) ions in lead borate glasses before and after heat treatment were measured. The more intense and narrowing luminescence lines suggest partial incorporation of Er(3+) ions into the orthorhombic PbF(2) crystalline phase, which was identified using X-ray diffraction analysis.

Optical transitions of Eu3+ and Dy3+ ions in lead phosphate glasses

Lead phosphate glasses containing Eu(3+) and Dy(3+) have been studied. Local structure was verified using Fourier transform (FT)-IR spectroscopy. Emission bands of Eu(3+) and Dy(3+) ions in lead phosphate glasses are observed in the visible spectral range, which correspond to 5D0→7F(J) (J=0,1,2,4) and 4F(9/2)→6H(J/2) (J=15,13,11) transitions, respectively. Shorter luminescence decays from excited states of Eu(3+) and Dy(3+0 are due to the presence of PbO in phosphate glass.

Understanding Eu(3+) emission spectra in glass

The emission spectra of the tripositive lanthanide ion Eu(3+) have often been employed to probe its environment in the solid state, and the intensity ratio of magnetic dipole ((5)D(0)-->(7)F(1)) and forced electric dipole ((5)D(0)-->(7)F(2)) transitions has been used to estimate the "degree of asymmetry" of a crystal site. From the site-selective, low temperature emission spectra of Eu(3+) doped into a glass, a new empirical relation has been found between the width of spectral features and the relative intensity of the (5)D(0)-->(7)F(0) zero phonon line. In order to explain the observations from experiments with excitation at different wavelengths, a generic quantitative relation has been developed from basic theory and validated from our experimental results. This work gives a deeper insight and understanding of the spectral characteristics of Eu(3+) electronic spectra in the visible region.