Local Structure Of Eu3 Research Articles

Structural and optical properties of europium-doped sodium-lead-antimony glasses

Antimony-sodium-lead glasses doped with varying amounts of europium were synthesized using the melt quenching technique. To investigate the mutual effects between the dopant and the glass matrix, various methods and techniques were employed to analyze and characterize the glass samples. These methods included X-ray diffraction (XRD) for justifying the amorphous nature of the samples, differential scanning calorimetry (DSC) for analyzing thermal properties, Fourier transform infrared (FTIR) spectroscopy for studying functional groups in the 1400–400 cm-1 range, and peak deconvolution techniques used to analyze the defect impact in the 1100–800 cm-1 band region. UV–VIS spectroscopy was utilized for absorption analysis, optical band gap estimation, and Urbach energy calculation. Photoluminescence spectroscopy was employed in the UV–VIS-NIR range to investigate excitation, emission, lifetime decay, and local structure of Eu3+ ions within the disordered matrix, characterized by high polarizability content. Judd-Ofelt analysis and radiative parameters were obtained from emission spectra using a 464 nm excitation wavelength. The estimation of the optical band gap revealed broadening and shrinking with increasing Eu3+ ion concentration. The excitation spectra showcased the potential for emission under two distinct excitation mechanisms: single-photon excitation (1PE) and two-photon excitation (2PE). The quality of emitted light color was characterized using CIE chromaticity coordinates.

Defect and spectroscopy properties of Eu-doped LiMgPO4 phosphors

In this work we used atomistic simulation based on lattice energy minimization combined with crystal field models to study the effects of Eu incorporation in the LiMgPO4 structure. We showed that the most favorable intrinsic defect type is formed by the anti-site defect, in which Li+ and Mg2+ ions exchange positions. The results revealed that Eu3+ prefers to enter in the Mg site with a LiMg' anti-site charge compensation. The local structure of Eu3+ was used to obtain the crystal field parameters and 7F1 energy sub-levels. Also, we estimated the photoionization cross-section of localized traps in the bandgap and associated it with the presence of defects to understand the high sensitivity.

Understanding the local structure of Eu3+- and Y3+-stabilized zirconia: insights from luminescence and X-ray absorption spectroscopic investigations

This study combines bulk structural and spectroscopic investigations of Eu3+- or Y3+/Eu3+ co-doped tetragonal and cubic zirconia polymorphs to gain an in-depth understanding of the solid solution formation process. Our bulk structural characterizations show that the dopant is homogenously distributed in the ZrO2 host structure resulting in an increase of the bulk symmetry with increasing dopant substitution (from 8 to 26 mol%). The local site symmetry around the Eu3+ dopant, however, determined with luminescence spectroscopy (TRLFS), remains low in all samples. Results obtained with X-ray pair distribution function and X-ray absorption spectroscopy show that the average coordination environment in the stabilized zirconia structures remains practically unchanged. Despite this very constant average dopant environment, site-selective TRLFS data show the presence of three nonequivalent Eu3+ environments in the ZrO2 solid structures. These Eu3+ environments are assumed to arise from Eu3+ incorporation at superficial sites, which increase in abundance as the size of the crystallites decrease, and incorporation on two bulk sites differing in the location of the oxygen vacancies with respect to the dopant cation.

Investigations on the spectroscopic properties and local structure of Eu3+ ions in zinc telluro-fluoroborate glasses for red laser applications

The strong red emitting Eu3+ doped Zinc telluro-fluoroborate glasses with the chemical composition (30–x)B2O3+30TeO2+16ZnO+10ZnF2+7CaF2+7BaF2+xEu2O3 (where x = 0.1, 0.25, 0.5, 1.0, 2.0 and 3.0 in wt%) have been prepared following the melt-quenching technique and their structural, spectroscopic behavior were characterized. The local structure and vibronic spectral analysis were performed in order to correlate them with the local field environment of Eu3+ ions in the prepared Zinc telluro-fluoroborate glasses on the basis of FTIR, Raman, Phonon sideband spectroscopy. Fundamental stretching units of Te–O bond in TeO3/TeO4 units, stretching of B–O bond in BO3/BO4 units and bending vibrations of Te–O–Te/B–O–B bonds were identified through FTIR and Raman spectral analysis. The Nephelauxetic intensity ratios (β) and bonding parameter (δ) values obtained from the absorption bands reveals the covalent nature of the Eu–O bond in the prepared glasses. Phonon sidebands appear around 505, 732 and 999 cm−1 results from the combined bending vibrations of Zn−O−Te and Te−O−Te in borate network, combined stretching vibrations of TeO4 trigonal bipyramidal (tbp) units with the formation of vitreous B2O3 due to the bending vibration of B–O–B linkages, and B−O bond stretching in BO4 units, stretching modes of terminal oxygens (B–O−) belong to the BO2O metaborate triangles respectively. The JO intensity parameters (Ωλ) and the asymmetric intensity ratio (R) values calculated from the emission spectra have been used to explore the nature of the bonding and asymmetry around the Eu-ligand field environment. The increasing Ω2 intensity parameters and R values confirms the higher asymmetry around the Eu3+ ions and covalency of Eu–O. The JO intensity parameters were used to estimate the radiative properties such as transition probability (A), stimulated emission cross-section (σPE), branching ratio values (β) and radiative lifetimes (τR) for the observed emission transitions. The excited state lifetime for the 5D0 level of the Eu3+ ions exhibit single exponential behavior for all the titled glasses and found to increase with the increase in Eu3+ ions concentration due to the higher asymmetry around Eu3+ ions. Further, emission intensities were characterized using CIE chromaticity diagram and the (x,y) chromaticity coordinates (0.63, 0.36) suggests the pure intense red emission obtained from the prepared glasses useful for laser applications at 616 nm.

Hydrothermal assisted sol–gel synthesis and multisite luminescent properties of anatase TiO2:Eu3+ nanorods

The relationship between local structure of Eu3+ ions and luminescence properties were discussed through site-selective spectroscopy at 10 K.

Broadband, site selective and time resolved photoluminescence spectroscopic studies of finely size-modulated Y2O3:Eu3+ phosphors synthesized by a complex based precursor solution method

Undoped and Eu3+-doped cubic yttria (Y2O3) nanophosphors of good crystallinity, with selective particle sizes ranging between 6 and 37 nm and showing narrow size distributions, have been synthesized by a complex-based precursor solution method. The systematic size tuning has been evidenced by transmission electron microscopy, X-ray diffraction, and Raman scattering measurements. Furthermore, size-modulated properties of Eu3+ ions have been correlated with the local structure of Eu3+ ion in different sized Y2O3:Eu3+ nanophosphors by means of steady-state and time-resolved site-selective laser spectroscopies. Time-resolved site-selective excitation measurements performed in the 7F0 → 5D0 peaks of the Eu3+ ions at C2 sites have allowed us to conclude that Eu3+ ions close to the nanocrystal surface experience a larger crystal field than those in the nanocrystal core. Under the site-selective excitation in the 7F0 → 5D0 peaks, energy transfer between the sites has also been observed.

Luminescence Efficiency Enhancement of BaZr(BO3)2:Eu with Si or Al Addition

Si4+ and Al3+ doped BaZr(BO3)2:Eu phosphors were prepared by solidstate reaction. BaZr(BO3)2:Eu3+, BaZr(BO3)2:Eu3+, Si4+ and BaZr(BO3)2:Eu3+, Al3+ were characterized by X-ray diffraction spectra (XRD) and photoluminescence spectra. After codoped with Si or Al, the charge-transfer state (CTS) band of Eu3+-O(2-) shows blue shift accompanied by increasing intensity due to shorter ionic radius and stronger electro negativity of Si or Al compared with Zr4+. The high value of asymmetric ratio R(2-1) and omega2 of BaZr(BO3)2:Eu3+ with Si or Al codoping indicates a less symmetrical local structure of Eu3+. This implies that the quantum efficiencies of the 5D0 level of these complexes can be enhanced by doping with Si and Al respectively. Calculation of the Judd-Ofelt parameters of Eu3+ under different crystal fields gives similar results.

Local structure of Eu3+ ions in fluorophosphate laser glass

A fluorophosphate laser glass doped with 1.0 mol% of Eu3+ ions has been prepared and studied by site-selective spectroscopy to explore the local structure of Eu3+ ions. Site-selective 5D0 → 7F1,2 emission spectra have been measured under resonant excitation to the 5D0 level at different wavelengths within the 7F0 → 5D0 band at 16 K. Using the Stark level positions of the 7F1 and 7F2 levels, crystal-field analysis has been carried out. The results suggest the existence of a unique kind of site for all the environments of Eu3+ ions in this glass.

Effect of growth temperature on Eu‐doped GaN layers grown by organometallic vapor phase epitaxy

AbstractWe investigated the effect of growth temperature on the luminescence properties of Eu‐doped GaN layers grown by organometallic vapor phase epitaxy (OMVPE). The dominant photoluminescence (PL) peak intensity at 621 nm, due to the intra‐4f shell transitions of 5D0‐7F2 in Eu3+ ions, became the highest when the sample was grown at 1000 °C. We consider three reasons for this temperature dependence. Firstly, Eu concentration became the highest when the sample was grown at 1000 °C. Secondly, Eu‐doped GaN layer grown at 1000 °C had the local structure of Eu3+ ions, which emitted at 621 nm preferentially. Thirdly, the density of screw and mixed dislocations decreased with increasing growth temperature. These results indicated that an appropriate growth temperature exists for strong Eu‐related luminescence from Eu‐doped GaN layer grown by OMVPE. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Parameters of luminescence and the local structure of Eu3+ centers in fluorogermanate glasses

The influence of the chemical nature of the local environment of Eu3+ ions on the parameters of luminescence of these centers in glasses of the (BaGeO3)1 − x − y(Al2O3)x(0.45CaF2 · 0.55MgF2)y (x = 0.25, y = 0; x = 0.17, y = 0.17; x = 0.15, y = 0.22; x = 0.07, y = 37.00; x = 0, y = 0.45) system is investigated. The oxidation state of europium atoms and the degree of homogeneity of their local environment in the glasses are determined using 151Eu Mossbauer spectroscopy.

Mechanism of the room-temperature persistent spectral hole burning in borate glasses doped with Eu3+

Spectroscopic properties and room-temperature persistent spectral hole burning mechanisms of Eu3+-doped borate glasses were investigated. The depth of the burnt hole increased with the amount of carbon powders (i.e., degree of reducing atmosphere). This was attributed to the formation of defects which can donate free electrons for the photoreduction of Eu3+→Eu2+. Holes survived >104 s at 20 K and approximately 40% of hole areas were preserved after annealing at 280 K. The photoreduction of Eu3+ to Eu2+ is a primary mechanism of hole burning and this hypothesis was supported by spectral hole properties, relaxation properties as well as changes in the local structure of Eu3+ in glasses.