Environment Of Rare-earth Ions Research Articles

Controlling the interfacial reactions and environment of rare-earth ions in thin oxide films towards wafer-scalable quantum technologies

Encapsulating the active layer containing rare-earth ions between undoped thick layers allows limiting interfacial reactions during thermal annealing and leads to narrower homogeneous and inhomogeneous linewidths.

Influence of some sesquioxides on up conversion in Ho3+−Er3+ co-doped PbO−SiO2 glass system

The glasses of the composition 37PbO–8Al2O3/ Sc2O3/ Y2O3−54SiO2: 1Ho2O3 (Holimium series), 37PbO–8Al2O3/ Sc2O3/ Y2O3−54SiO2: 1Er2O3 (Erbium series) and 37PbO–8Al2O3/ Sc2O3/ Y2O3−54SiO2: 0.5Ho2O3+0.5 Er2O3 (codoped series) have been synthesized. Optical absorption and fluorescence spectra in the spectral range 300-2000 nm were studied at ambient temperature. The Judd-Ofelt theory could successfully be applied to characterize the optical absorption and emission spectra of these ions. The comparison of branching ratios β values of blue, green and red emissions for both the series of the glasses showed the largest values for glass mixed with Y2O3. A noticeable enhancement in the intensities of blue, green and red emission levels has been observed due to co-doping and is found to be the highest for the glasses mixed with Y2O3. The reasons for this enhancement have been analyzed in the light of varying environment of rare earth ions due to different sesquioxides in the glass network. The Al3+, Sc3+ and Y3+ are expected to be coordinated by three SiO4 tetrahedral ligands. Two of the oxygen ions associated with each tetrahedron is assumed to be non-bridging ions forming ionic bonds with these trivalent ions. However in case of Y3+ ions silicate tetrahedra must be moved more outward since the ionic radius of this ion is more when compared with that of Al3+ and Sc3+ ions. In view of this, although three ions are linked in triangle with SiO4 structural units, the octahedra of yttrium ion is more distorted when compared with that of the other two ions

Origin of domain wall induced magnetoelectricity in rare-earth iron garnet single crystals and films

ABSTRACTIn this article, we discuss the mechanism of magnetoelectric effect in rare-earth iron garnets related to the low symmetry environment of rare-earth ions and magnetic inhomogeneity created by iron subsystem. Low symmetry environment of rare-earth ions leads to antiferroelectric arrangement of their electric dipole moments and favors releasing of iron garnets ferroelectricity. Magnetic domain walls act as the sources of non-uniform effective magnetic field breaking antiferroelectric ordering. We calculate electric polarization in a vicinity of Bloch domain walls in rare-earth iron garnet crystals and films, pick out their distinguished features, and touch upon experimental evidences of domain wall induced magnetoelectricity.

Spectroscopic manifestations of local crystal distortions in excited 4f states in crystals of huntite structure

Optical absorption spectra of YbAl3(BO3)4, TmAl3(BO3)4 and TbFe3(BO3)4 trigonal crystals have been studied in temperature range 2–300 K. Temperature behavior of absorption lines parameters has shown, that during some f-f transitions the local environment of rare earth ions undergo distortions, which are absent in the ground state.

Rare earth ion clustering behavior in europium doped silicate glasses: Simulation size and glass structure effect

Understanding the atomic structures, especially the local environment of rare earth ions and their distribution and clustering, is critical for rare earth containing glasses in photonic devices, as well as model systems for nuclear waste immobilization. In this paper, we've studied the structure of Eu2O3-doped silica and sodium silicate glasses using molecular dynamics simulations for systems ranging from around 1500 to around 24,000 atoms with the purpose to understand the simulation system size and the glass composition and structure effect on the local environment and clustering behavior of rare earth ions with low rare earth oxide concentration (~1mol%). In silica glasses, Eu–O distances and coordination numbers are found to be in the ranges of 2.19–2.22Å and 4.6–4.8, respectively in the series. The existence of Eu clusters and short Eu–Eu distances in the range of 3.40–3.90Ǻ was observed. In the modified sodium silicate glass, on the other hand, europium ions were found to have higher coordination number of around 5.8, as well as a narrower coordination distribution, and longer Eu–O distance of around 2.32Ǻ. Eu ions were also found to be in much better dispersion and lower probability to form clusters. The clustering behavior of europium ions was investigated by comparing the probability of clustering in the simulated glass with those from a random distribution. It was found that clustering behavior is sensitive with the system size. For systems with over 12,000 atoms, consistent results were obtained in terms of probability of clustering as compared to a random distribution. But for smaller systems, the clustering behavior can vary from sample to sample. The results suggest that for low doping level it is critical to have sufficient number of rare earth ions in order to obtain statistical meaningful results on the local environment and clustering.

Spectroscopy features of Pr 3+ and Er 3+ ions in Li 2O–ZrO 2–SiO 2 glass matrices mixed with some sesquioxides

The glasses of the composition Li 2O–ZrO 2–SiO 2: Pr 2O 3/Er 2O 3 mixed with three interesting sesquioxides (viz., Al 2O 3, Sc 2O 3, Y 2O 3) were synthesized. Optical absorption and fluorescence spectra (in the spectral range 350–2100 nm were studied at ambient temperature. The Judd–Ofelt theory was applied to characterize the absorption and luminescence spectra of Pr 3+ and Er 3+ ions in these glasses. Following the luminescence spectra, various radiative properties like transition probability A, branching ratio β and the radiative life time τ for different emission levels of two rare earth ions have been evaluated. The radiative life times for the upper levels 3P 0 (Pr 3+) and 4S 3/2 (Er 3+) have also been measured and quantum efficiencies were estimated. The variations observed in these parameters were discussed in the light of changing environment of rare earth ions due to mixing of different sesquioxides in the glass network.

Nd 3+ sensitized blue upconversion luminescence in Nd 3+/Pr 3+ co-doped Ge–Ga–S–CsBr chalcohalide glasses

The effect of CsBr/Ga ratio on the blue upconverted emission from Nd 3+/Pr 3+ in Ge–Ga–S–CsBr chalcohalide glasses was investigated. When CsBr/Ga was smaller than unity, the energy transfer from Nd 3+ to Pr 3+ ions was dominant and blue emission centered at ∼ 495 nm (Pr 3+: 3P 0 → 3H 4) was observed. On the contrary, the intensity of the upconversion luminescence from Nd 3+ increased at the expense of the blue emission when CsBr/Ga ratio exceeded unity. The possible relationship between the composition-dependent blue emission and the local environment of rare earth ions was discussed.

Emission sensitization and mechanisms of electron-excitation migration in structures based on III-nitrides doped with rare-earth elements (Eu, Er, Sm)

The effect of doping with Eu, Er, and Sm rare-earth ions on the shape of the luminescence spectrum for heterostructures with GaN/In x Ga1 − x N (0.1 < x < 0.4) quantum wells and from p-GaN〈Mg〉/n-GaN and p-AlGaN/n-GaN junctions is investigated. The results of measurements of the electroluminescence of these structures correlate with the previous data on photoluminescence and Mossbauer spectroscopy. It is shown that it is the GaN “yellow” (5000–6000 A) band that plays the important role in the excitation of intracenter states in the structures with several GaN/InGaN quantum wells doped with Eu and Sm. In this case, Eu is most likely the sensitizer for Sm. Additional introduction of 3d metal (Fe57) in p-GaN〈Mg〉/n-GaN:Eu results in the realization of intracenter transitions in Eu3+: 5 D 0 → 7 F 1 (6006 A), 5 D 0 → 7 F 2 (6195 A), 5 D 0 → 7 F 3 (6627 A), and 5 D 1 → 7 F 4 (6327 A) due to the occurrence of new, efficient channels of excitation transfer to intracenter states and in the effect of Fe on the local environment of rare-earth ions including due to the f–d hybridization enhancement.

Valence and environment of rare earth ions in CaAl 2O 4:Eu 2+,R 3+ persistent luminescence materials

The existence of the different R 2+/R 3+/R IV (R: rare earth) ions as well as the modifications in the structural environment around the dopant and co-dopants in CaAl 2O 4:Eu 2+,R 3+ persistent luminescence materials was studied by L III edge X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) measurements at Hamburger Synchrotronstrahlungslabor (HASYLAB) at Deutsches Elektronen-Synchrotron (DESY) (Hamburg, Germany). The measurements were carried out at 10 and 296 K for selected rare earth (co-)dopants (Eu 2+; Ce 3+, Nd 3+, Sm 3+, and Yb 3+). The XANES results indicated the co-existence of both divalent and trivalent europium in all co-doped CaAl 2O 4:Eu 2+,R 3+ materials, but only divalent europium in CaAl 2O 4:Eu 2+. The measurement temperature did not affect the XANES results. The interatomic distances extracted from the EXAFS data of the CaAl 2O 4:Eu 2+,R 3+ materials indicated that co-doping creates distortions around the Eu 2+ ions suggesting dopant aggregation.

Optical spectroscopy of Eu3+ and Tb3+ doped glass ceramics containing LiYbF4 nanocrystals

The Eu3+ and Tb3+ doped glass ceramics containing tetragonal LiYbF4 nanocrystals were prepared. The Stark splitting emission, the low electric dipole D50→F72 transition, and the long lifetime of Eu3+ evidenced the partition of rare earth into LiYbF4. For Tb3+ doped glass ceramic, intense ultraviolet emission of Tb3+: G56, D53→F76 transition via cooperative sensitization of Yb3+ and bright blue cooperative luminescence originated from the coupled state of Yb3+–Yb3+ ionic pairs were achieved under 976 nm excitation, ascribing to the low-phonon-energy environment of rare earth ions enriched in nanocrystals and the efficient Yb3+–Tb3+ or Yb3+–Yb3+ interionic interactions.

Nanocrystallization of lanthanide trifluoride in an aluminosilicate glass matrix: dimorphism and rare earth partition

A systematic synthesis of homogeneously distributed lanthanide trifluoride (from LaF3 to LuF3) nanocrystals in the same aluminosilicate glass matrix was reported. These fluorides exhibit dimorphism, i.e., the hexagonal structure for those from LaF3 to GdF3 and the orthorhombic one for those from TbF3 to LuF3 (including YF3). The Eu3+ emission spectra evidenced the partition of the doped rare earth ions into the LnF3nanocrystals, and as an example, the intense ultraviolet upconversion emissions were achieved in the Tm3+ : YbF3nanocrystals containing composite due to the low-photon-energy environment of rare earth ions. These nano-composites may find potential applications in solid-state lasers, 3D displays, amplifiers and other optoelectronic devices.

Gel combustion synthesis and luminescence properties of nanoparticles of monoclinic SrAl2O4:Eu2+,Dy3+

Nanoparticles of strontium aluminate phosphors co-activated by Eu2+ and Dy3+ have been prepared by heating the precursors obtained from nitrate salt–ammonium acetic–urea–gel combustion process at temperature of 1150°C in a weak reductive atmosphere of thermal carbon. Transmission electron microscope (TEM) images revealed that the hollow nanoparticles of SrAl2O4:Eu2+,Dy3+ were formed below 1150°C, while the needle or rod-shaped particles were formed at 1200°C. The XRD patterns indicated that the resulted SrAl2O4:Eu2+,Dy3+ nanoparticles contained distorted monoclinic lattice. The environment of rare earth ion in SrAl2O4 lattice was investigated by using Eu3+ as ion probe, and the results indicated that there were two kinds of sites occupied by Eu3+, one was centro-symmetrical environment, while the other not. The luminescence and the afterglow properties of the hollow nanoparticles of SrAl2O4:Eu2+,Dy3+ were also investigated.

Luminescent properties of Eu 3+-activated lithium rare earth borates and oxyborates

The luminescence characteristics of Eu 3+ in the borates Li 6Y(BO 3) 3 and Li 3La 2(BO 3) 3 and the recently discovered oxyborates LiLa 2O 2BO 3, LiLn 6O 5(BO 3) 3 (Ln=Y,Gd) and Li 2Lu 5O 4(BO 3) 3 have been investigated and compared to those in the borates LnBO 3 (Ln=La,Y) and the oxyborates “Ln 3BO 6” (Ln=La,Gd). The probability of electric dipole f–f transitions is generally markedly higher in oxyborates than in borates. This is ascribed to the highly anisotropic environment of rare earth ions and the low position of the charge transfer states. Consequently, the Eu 3+-activated oxyborates are characterized by a deeper red emission and faster decay.

Intensities of f-f transitions in Pr3+ and Dy3+ in glasses in the near-IR spectral range

The absorption spectra of Pr3+ and Dy3+ ions in three glass matrices (SiO2-P2O5-GeO2, Al2O3-B2O3-SiO2, and LiB3O5) are thoroughly studied in the near-IR spectral range (4600–14 300 cm−1). The temperature dependences of the intensity, the width, and the location of the absorption bands observed are investigated for the first time. It is shown that the f-f transitions in the studied glasses are allowed by static odd distortions in the environment of the rare-earth ions and these distortions decrease with an increase in temperature. A comparative analysis of the absorption band parameters and their temperature behavior in different materials makes it possible to determine the differences in magnitudes, symmetries, and dispersions of the distortions in the nearest environment of rare-earth ions in different glasses.

Determination of coordination environment of rare earth ions with cooperative vibronic spectroscopy

The ligand type and the number of each type of ligand can be determined with CV spectra of RE ions. This technique provides a simple method to measure the number of metal-coordinated water molecules and in this technique no D2O replacement is needed. Therefore, the range of ligands whose binding numbers can be determined directly is also extended. This spectroscopic technique is not limited by the form of sample and has high detecting sensitivity. It can be used as a structure analysis method for usual samples, and more important, it can also be used as a spectral probe of the coordination environment of RE ions in biological samples. So CV technique is especially important for studying the biological functions of RE elements.

Fluorescence line narrowing spectroscopy of europium(III) ions in a fluorozirconate glass 36093

The environment of rare-earth ions in fluorozirconate-based glasses was investigated by fluorescence line narrowing spectroscopy using Eu3+ as a local site probe. A pulsed tuneable dye laser was used to excite the5D0 level of Eu3+, and the subsequent5D0 →7Fj fluorescence spectra were recorded as a function of exciting wavelength. A series of5D0 excitation spectra was also taken, the emission monitored at various positions in the fluorescence spectra. The extra features visible in some of these spectra are not due to two different site distributions as previously thought, but are an effect caused by simultaneous excitation into the5D0 phonon side band.