Properties Of Lanthanide Ions Research Articles

Intense upconversion luminescence of Er 3+/Yb 3+ codoped oxyfluoride borosilicate glass ceramics containing Ba 2GdF 7 nanocrystals

Er 3+/Yb 3+-codoped transparent oxyfluoride borosilicate glass ceramics containing Ba 2GdF 7 nanocrystals were prepared and spectroscopic properties of rare earth ions were investigated. Fluoride nanocrystals Ba 2GdF 7 were successfully precipitated in glass matrix, which was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) results. In comparison with the as-made precursor, significant enhancement of upconversion luminescence was observed in the Er 3+/Yb 3+ codoped oxyfluoride glass ceramics, which may be due to the variation of coordination environment around Er 3+ and Yb 3+ ions after crystallization. The transition mechanisms of the green and red upconversion luminescence were ascribed to a two-photon process, and that of the blue upconversion luminescence was a three-photon process.

Magnetic properties of rare earth ion (Sm 3+) added nanocrystalline Mg–Cd ferrites, prepared by oxalate co-precipitation method

Nanocrystalline ferrite powder having the general formula Mg 1− x Cd x Fe 2O 4+5% Sm 3+ ( x=0, 0.2, 0.4, 0.6, 0.8 and 1.0) was synthesized by chemical oxalate co-precipitation technique. The synthesized powder was characterized by X-ray, IR and SEM techniques. The XRD analysis confirms cubic spinel phase with orthoferrite secondary phase. The lattice constant increases with increase in Cd 2+ content ( x). It is smaller than that for pure Mg–Cd ferrites. The average crystallite size lies in the range 28.69–32.66 nm. Saturation magnetization and magnetic moment increase with cadmium content up to x=0.4 and decrease thereafter. This is attributed to the existence of localized canted spin. The decrease in saturation magnetization and magnetic moment beyond x=0.4 is due to the presence of triangular spin arrangement on B-site. Coercivity and remanent magnetization decrease while Y–K angles increase with Cd 2+ content. The Sm 3+ addition improves the magnetic properties.

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 2O 3 ratios in glass composition, giving important contribution to the luminescence intensities associated to 5D 0– 7F 2 and 5D 0– 7F 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.

Luminescence and X-ray Diffraction Studies of Rare Earth Doped Silica Sol-Gel Glass

We present recent work exploring the effects of aluminum co-doping on the luminescent properties of rare earth ions in sol-gel glasses. Using x-ray diffraction techniques we have identified the formation of aluminum rich nano-crystals in silica glass annealed to high temperatures. We discuss implications of these results in understanding the impact aluminum co-doping has on rare earth luminescence in sol-gel glass.

Polarization selection rules and optical transitions in terbium activated yttrium tantalate phosphor under x-ray, vacuum-ultraviolet, and ultraviolet excitations

The terbium-activated yttrium tantalite (YTaO(4):Tb(3+)) phosphor is of great interest due to the interesting spectroscopic properties of rare earth ions in crystals and also practical use in x-ray imaging. Using the group-theoretical approach, we analyze the selection rules for the transition between Stark components of Tb(3+) in symmetry of the actual crystal field and the polarization for the allowed transitions. The luminescence upon UV, vacuum-ultraviolet (VUV), and x-ray excitation is presented and discussed. The YTaO(4):Tb(3+) phosphors are found to be efficient VUV-excited luminescent materials that could be used not only in x-ray intensifying screens, but also in mercury-free fluorescent lamps or plasma display panels.

Role of PbO substitution by PbF2 on structural behavior and luminescence of rare earth-doped lead borate glass

Structural behavior and luminescence properties of rare earth ions (Pr 3+ , Eu 3+ , Er 3+ ) in oxide and oxyfluoride lead borate glasses have been studied using X-ray diffraction and spectroscopic methods. Substitution of PbO by PbF 2 results in decreasing of the number of tetrahedral BO 4 units, which was observed for Pr 3+ and Eu 3+ ions in lead borate glasses using infrared spectroscopy. In contrast to oxyfluoride lead borate glasses, several diffraction lines due to crystalline ErBO 3 phase were identified for Er-doped oxide sample. Luminescence spectra for rare earth ions in lead borate based glasses have been analyzed, where PbO was totally substituted by PbF 2 .

Rare Earth-Activated Silica-Based Nanocomposites

Two different kinds of rare earth-activated glass-based nanocomposite photonic materials, which allow to tailor the spectroscopic properties of rare-earth ions: (i) Er3+-activated SiO2-HfO2waveguide glass ceramic, and (ii) core-shell-like structures of Er3+-activated silica spheres obtained by a seed growth method, are presented.

Crystal Structures of Two Calix[4]arene Isomers with Benzaldehyde Moiety and Their Photophysical Properties with Terbium(III) Ions

AbstractTwo calix[4]arene isomers with benzaldehyde moieties, i.e., 5,11,17,23‐tetra‐tert‐butyl‐25,27‐bis[2‐(o‐formyl‐phenoxy)ethoxy]‐26,28‐dihydroxycalix[4]arene (3) and 5,11,17,23‐tetra‐tert‐butyl‐25,27‐bis[2‐(p‐formylphenoxy)‐ ethoxy]‐26,28‐dihydroxycalix[4]arene (4), were synthesized according to a newly designed route in high yields, and their crystal structures have been determined by X‐ray crystallographic study. The photophysical behavior on com‐plexation of calix[4]arene derivatives 3 and 4 with terbium(III) nitrate was investigated in anhydrous acetonitrile at 25°C by UV‐Vis and fluorescence spectroscopies. The crystallographic structure of 3 indicated that the eight oxygen atoms formed a preorganized ionophoric cavity due to intramolecular π‐π stacking, which could encapsulate lanthanide ions tightly. In sharp contrast, the compound 4 formed a linear array by intermolecular π‐π stacking, hence the oxygen atoms of pendant arms could not coordinate with metal ions, giving a poor binding ability to Tb3+. The absorption spectra of 3 with Tb3+ showed clearly a new broad intense absorption at 385 nm. Interestingly, the narrow emission line spectrum has also been observed for compound 3 with Tb3+, and the results obtained were discussed from the viewpoint of energy transfer mechanism between host structures and the properties of lanthanide ions.

Spectroscopic assessment of rare-earth activated planar waveguides and microcavities

This paper deals with glass-based photonic structures, used to control and modify the optical and spectroscopic properties of rare earth ions. The spectroscopic assessment of sol–gel-derived planar waveguides and 1D photonic band gap structures is reported. The spectroscopic, optical, and structural properties of planar waveguides with (100 − x)SiO 2– xHfO 2– yErO 1.5 with y = 0.3, 0.01; and x = 10, 20, 30, 40 have been investigated by photoluminescence and Raman spectroscopy. The radiative quantum efficiency of the 4I 13/2 metastable state of Er 3+ ions is between 84 and 88% depending on the Si/Hf molar ratio. The sol–gel-derived one-dimensional cavity was realized by a Eu 3+-activated dielectric layer placed between distributed Bragg reflectors (DBRs).

Effective operators and spectroscopic properties

In 1968, Wybourne1Brian Wybourne died unexpectedly on 26 November, 2003; this paper was presented during a Special Session devoted to the Judd–Ofelt theory to demonstrate Wybourne’s impact upon the spectroscopy of f-electron systems.1 [J. Chem. Phys. 48 (1968) 2596] asked two major questions while pointing out that a few years earlier, “Judd and Ofelt considered only second-order contributions to the oscillator strength:1.Are the higher-order contributions significant?2.What new angular-dependent terms enter when the higher-order contributions are considered?”In the present paper, the answers to these questions are discussed in the form of a report woven onto the background of Wybourne’s publication. The very last sentence of his paper might be taken as an obligation and also as a source of inspiration for all of us who have been trying to describe the properties of rare earth ions over the years. Indeed, he remarks: “At this state (1968) there would seem to be little point in extending calculations to higher orders until actual numerical estimates of the relative importance of the second- and third-order contributions are established.” In this context, the present analysis is performed up to the third-order terms, and the new effective operators are discussed. In addition, to fulfill the demand for “actual numerical estimates”, the results of ab initio calculations are presented to illustrate the hierarchy of important physical mechanisms that contribute to the f↔f transition amplitude.

Correlation of radiative properties of rare earth ions (Pr3+ and Nd3+) in chlorophosphate glasses—0.1 and 0.5 mol% concentrations

Optical properties of chlorophosphate glasses of the type 50P2O5−30Na2HPO4−20RCl (R = potassium and lead) activated by 0.1 and 0.5 mol% of Pr3+ and Nd3+ have been investigated. Optical band gaps (E opt)have been reported for 0.1 and 0.5 mol% concentrations of Pr3+ and Nd3+ doped potassium and lead chlorophosphate glasses. Energy levels and optical transitions of Pr3+ and Nd3+ are assigned. Spectroscopic parameters (E 1, E2,E 3,ξ4f and α), spectral intensities (f expt), Judd-Ofelt intensity parameters (Ω2, Ω4 and Ω6) and radiative lifetimes (ΤR) are correlated for 0.1 and 0.5 mol% concentrations of these two ions in potassium and lead chlorophosphate glasses.

Preparation conditions and optical properties of rare earth ion (Er3+ and Eu3+)-doped alumina films by the aqueous sol–gel method

Transparent alumina and rare earth ion (Er3+ and Eu3+) highly doped alumina films (15 mol %) were prepared by the aqueous sol–gel method, in order to examine the effects of various preparation conditions on the structure and optical properties of doped films. The results showed that when the gel was heat treated, it lost free and bound water and was converted into the oxide by way of a series of intermediate phases although the oxide as a whole remained structureless. The thermogravimetric analysis curve showed a marked weight loss in the temperature range of 100–500 °C and the slow loss continuing at higher temperature of 800 °C. High doping may reflect noncrystalline structure of alumina. The fluorescence of Eu3+ sensitive of microstructure increased especially corresponding to this weight loss with treatment. The Ω2 indicative of the asymmetric environment of Er3+ showed a similar increase. Concentration quenching for doped films treated at 800 °C was not significant in this concentration range. Lifetimes increased with increasing treatment temperature, similar to above increase.

Stark levels analysis for Er 3+-doped oxide glasses: germanate and silicate

A model of effective crystal field Hamiltonian based on the principle of descending symmetry and using the symmetry group chain scheme is proposed to describe the average of local symmetries occupied by rare earth (RE) ions in glasses. Only three crystal field parameters, one for each rank, have to be fitted in this Hamiltonian. Based on the absorption and emission spectra measured in a conventional way at 13 K, the Stark levels in manifolds from 4I 15/2 to 2H 9/2 and their widths of Er 3+ in two oxide glasses: germanate and silicate, are investigated. In the process, the scalar crystal field strength, homogeneous and inhomogeneous effective widths of levels are analyzed, and the former models and results about optical properties of rare earth ions in glasses are discussed. The cubic crystal field term is found to give the major contribution to the crystal field strength around the rare earth ion when the weak axial distortion completely removes the degeneracy.

Optical properties of rare earth ion (Nd 3+, Er 3+ and Tb 3+)-doped alumina films prepared by the sol–gel method

Rare earth ion (Nd 3+, Er 3+ and Tb 3+)-doped alumina films were prepared by the sol–gel method using aqueous alumina sol. The effects of dopant concentration and treatment temperature on the optical properties, absorption and emission were examined for the doped films. Alumina films prepared by this method gave a high dopant concentration (0–15 mol% per alumina). Significant concentration quenching did not occur in this concentration range. The emissions from 5D 3 and 5D 4 of Tb 3+-doped film reflected sensitively a matrix environment around Tb 3+ ions. Er 3+- and Nd 3+-doped alumina films resonantly excited by cw Ti–sapphire laser (800 nm) showed upconversion emission at room temperature. The former gave 548 nm ( 4 S 3/2→ 4 I 15/2 ) and 640 nm ( 4 F 9/2→ 4 I 11/2 ) signals, and the latter 640 nm ( 4 G 7/2→ 4 I 11/2 ), which were dependent on alumina.

Crystal field analysis of Er 3+-doped glasses: germanate, silicate and ZBLAN

A simple model of average crystal field Hamiltonian based on the principle of descending symmetry and using the group chain scheme is proposed to describe the average of local symmetries occupied by rare earth ions in a disordered medium. Only three crystal field parameters, one for each rank, have to be fitted in this Hamiltonian. Based on the absorption and emission spectra measured in a conventional way at 13 K, the Stark levels in manifolds from 4I 15/2 to 2G(1) 9/2 of Er 3+ in two oxide glasses: germanate and silicate and one fluoride glass: ZBLAN, are investigated. The scalar crystal field strength is analysed, and former models about optical properties of rare earth ions in glasses are discussed. The crystal field strength is decreasing from silicate to germanate and finally to fluoride glass. In the oxide glasses, the rare earth ions can occupy positions with symmetries distorted from D 4, D 4 h and their isomorphic groups. In the fluoride glass, the rare earth ions can occupy positions more freely with symmetries distorted from D 4, D 4 h and also from D 3, D 3 d and their isomorphic groups. In all studied glasses, the cubic crystal field terms give the major contribution to the crystal field strength around the Er 3+ ion when the weak axial distortion removes completely the degeneracy.

Luminescent inorganic networks

AbstractSilica‐based inorganic networks combined with organic rare earth complexes should lead to a new class of luminescent materials, adding the chemical stability of silica to the strong UV absorption of organic ligands and the emissive properties of rare earth ions. This concept is demonstrated by the preparation of silica xerogels containing benzoic acid in its network and subsequent reaction (ion exchange) of these gels with terbium chloride solution. The product yields green luminescence similar to the one of solid terbium benzoate. Alternatively, complete rare earth complexes (example: europium thenoyltrifluoracetonate) may be immobilized in silica xerogels, yielding luminescent hybrid materials.

Intermolecular energy transfer from coumarin-120 to rare earth ions (Eu 3+, Tb 3+) in silica xerogels

Co-doped with coumarin-120 (C120) and rare earth ions (Eu 3+and Tb 3+) in silica xerogels via sol–gel technique, the fluorescence properties of rare earth ions and the energy transfer process between C120 and rare earth ions were studied. The characteristic fluorescence intensities of Eu 3+and Tb 3+ions can be increased by a factor of 35 and 8, respectively, as a result of the sensitization of C120 absorption at about 344 nm. The sensitized emission of rare earth ions is through intermolecularly resonant exchange interaction. Because of fluorescence enhancement accompanied by concentration quenching of C120, the fluorescence intensities of Eu 3+and Tb 3+increase to maximum when the C120 doping concentration is of 0.1 mol%.

Chemical bond properties of rare earth ions in crystals

By using the dielectric description theory of ionicity of solids, chemical bond properties of rare earth ions with various ligands are studied. Calculated results show that chemical bond properties of the same rare earth ion and the same ligand in different crystals depend on the crystal structures. In a series of compounds, chemical bond properties of crystals containing different rare earth ions are similar. The magnitude of covalency of chemical bonds of trivalent rare earth ions and various ligands has an order like F<Cl<Br<As<Sb.

Are the odd-rank crystal field parameters independent quantities?

The relation between various odd-rank crystal field parameters is discussed in the context of the theoretical description of the spectroscopic properties of rare earth ions in crystals.

The luminescent properties, thermal stability of phthalic acid and energy transfer from phthalic acid to Tb 3+ in sol—gel derived silica xerogels

In recent years, the energy transfer between different rare earth ions and the luminescent properties of rare earth ions have been studied extensively. However, the research of luminescent properties, thermal stability and structural variations of organic compounds, as well as their energy transfer to rare earth ions in silica xerogel, have not been reported. Organic—inorganic composites have even more efficient luminescence than pure rare earth ions. We describe the fabrication of silica xerogels doped with phthalic acid and Tb 3+, their luminescent properties and thermal stability. The results show that, in silica xerogels, phthalic acid can exist steadily at 300 °C, and it can transfer the energy that it has absorbed to Tb 3+.