Rare-earth Solubility Research Articles

Nd Solubility in RS-Ga2S3 (R=Sr, Ba) Glasses

Nd solubility is evaluated in SrS- and BaS-Ga2S3 glasses using a series of absorption measurements. The result reveals that Nd up to 2-3mol% can be dissolved in these glasses. Rare-earth solubility in sulfide glasses is discussed in terms of the ionicity of chemical bonds. Raman spectroscopy suggests that Nd ions play a role of modifiers to the networks of GaS4 tetrahedra in a similar manner of the alkaline-earth ions. The limitation of Nd solubility is related to glass-forming ability during the cooling process of alkaline-earth gallium sulfide melts.

Clustering of rare earths in GeAs sulfide glass

Clustering of rare-earth dopants in GeAs sulfide glasses was studied by fluorescence spectroscopy of Pr-doped glasses and by EPR measurements of Gd-doped samples. The linewidth of the g ∼ 2 resonance of Gd 3+, as well as the relative intensity of emission from the 1D 2 level of Pr 3+, was used as a relative measure of rare-earth clustering. Rare earths were found to have low solubility in uncodoped GeAs sulfide glasses, which also displayed poor fluorescence efficiency due to severe clustering. Codoping such glasses with Ga greatly enhanced rare-earth solubility and dispersal, particularly for Ga:rare earth ratios ≥ 10:1, as evidenced by the narrower EPR resonances and more intense luminescence of Gd- and Pr-doped glasses, respectively. In, P and Sn were also observed to ‘decluster’ rare earths, although less efficiently than Ga, whereas codoping with I was found to have no effect on clustering. These phenomena are explained by a structural model in which (1) rare-earth dopants and codopants are spatially associated and (2) rare-earth dispersal is accomplished by a statistical distribution of codopants in tetrahedral network sites.

WDM Systems in the C-Band Using Er 3+ -Doped Tellurite Optical Waveguide Amplifiers

A 16-channel, 2.5 Gb/s, wavelength-division multiplexing system is analyzed with its channels allocated in the 1.52-1.56 w m wavelength region in order to increase the usable amplifier bandwidth to , 45 nm. To avoid amplified spontaneous emission (ASE) noise and the nonuniform signal gain in the wavelength region, an amplifier module consisting of an Er 3+ -doped tellurite waveguide amplifier, an ASE filter, and two concatenated long-period grating filters are proposed. A tellurite-based amplifier was chosen as the amplifying element because of its broad emission bandwidth (~80 nm), its high emission cross section (6.44 2 10 -25 m 2 ), and its high rare-earth ion solubility. The amplifier model is based on propagation and populationrate equations and includes both uniform and pair-induced up-conversion mechanisms. It is solved numerically by combining finite elements and a Runge-Kutta algorithm. The analysis predicts that using the proposed amplifier module, the channels may be transmitted to a maximum distance of 1800 km, finding applications in large optical networks where either many wavelengths are required or channel spacing must be large.

Investigation on the Cu–Cr–RE alloys by rapid solidification

The paper presents a process where Cu–Cr–RE alloys are produced by rapid solidification powder metallurgy, composite green compact, extrusion and sinking. The lattice parameter of the copper-rich solid solution in powders is determined by X-ray diffraction. A significant increase in the extension of the solid solubility of chromium and rare-earth in copper is achieved with this process. The microstructures of the alloys are examined by transmission electron microscopy. Hardness and tensile properties are evaluated. The strengthening mechanism of alloys includes fine grain, dispersion and precipitation strengthening. The electrical conductivity is higher than the conventional Cu–Cr and Cu–Al 2O 3 alloys.

Trace element and isotopic evidence for REE migration and fractionation in salts next to a basalt dyke

Neodymium and Sr isotopic compositions and the rare earth elements (REE) distribution patterns have been determined in salts adjacent to a basaltic dyke along 2 parallel horizontal profiles. The salts, originally consisting of carnallite (KMgCl 3 · 6H 2O), have been transformed during basalt intrusion mainly into halite (NaCl) and sylvite (KCl) by fluids saturated in NaCl. The Sr isotope data suggests that much more fluid penetrated the upper than the lower horizon. The Nd isotope data shows that in the upper horizon, where fluid flow was stronger, Nd is essentially derived from the basalt. In contrast, in the lower horizon a strong salt Nd component is present. The REE data document in both horizons is a strong depletion of Ce, Pr, Nd, Sm and Eu with increasing distance from the basalt. This depletion of the light rare earths (LREE) is stronger in the upper horizon where fluid flow was stronger. The authors suggest that this REE fractionation is more likely due to precipitation of LREE-enriched accessory minerals such as apatite, than to differential REE solubility caused by selective REE complexation. This finding is of interest for REE behaviour in brines in general, and for the behaviour of radioactive REE and actinides in a salt repository for high-level nuclear waste in particular.

Emission properties of the [formula omitted] transition in Er 3+- and Er 3+/Tm 3+-doped Ge–Ga–As–S glasses

Ge–Ga–As–S glasses were investigated to develop efficient host materials for the Er 3+:2.7 μm fiber lasers. Ge 30Ga 1As 9S 60 and Ge 30Ga 2As 6S 62 (all in at.%) glasses show good thermal stability and high rare-earth solubility up to 0.3 mol%. Mid-infrared emission with a peak wavelength of 2.76 μm and bandwidth of ∼120 nm was observed in Er 3+- and Er 3+/Tm 3+-doped Ge 30Ga 2As 6S 62 glasses. Codoping of Tm 3+ significantly reduced the lifetime of the Er 3+: 4 I 13/2 level due to the energy transfer of Er 3+: 4 I 13/2→ Tm 3+: 3 F 4 . Thus, the population inversion between the 4 I 11/2 and 4 I 13/2 levels in Er 3+ became possible. In Er 3+-doped glasses, the rate of cross-relaxation for the 4 I 11/2 level was approximately 11 times faster than that for the 4 I 13/2 level.

Increased rare earth solubility in As–S glasses

Praseodymium-containing glasses of the composition As 40− x Ga x S 60 (0.05 < x < 0.5; 300 and 600 weight-ppm Pr 3+) and As 37.8Ge 1.3Ga 0.5S 60.4 (760 weight-ppm Pr 3+) have been prepared by melting constituent elements and compounds in sealed quartz glass ampoules. The improvement of the Pr 3+ solubility in arsenic sulphide by co-doping with gallium and germanium leads to a suitable level for optical active applications up to 1000 ppm by weight. Fibres were drawn from bulk glasses by the crucible method. They have losses in the pump and signal region of 0.8 dB m −1, fluorescence with maximum at 1337 nm, a full width at half maximum of 74 nm and excellent corrosion stability. The –OH and –SH impurities were determined by Fourier Transform Infrared (FTIR) spectroscopy. Attenuation in the VIS and NIR regions and fluorescence spectra and lifetimes were investigated in the fibres. From the results, a model of glass formation including the co-dopants and the effects of impurities on the structure is proposed.

Raman spectroscopic analysis on the solubility mechanism of La 3+ in GeS 2–Ga 2S 3 glasses

In comparison to other chalcogenide glasses, Ge–Ga–S glasses have the largest rare-earth solubility. Raman spectra of GeS 2–Ga 2S 3 glasses contain two bands at 265 and 385 cm −1 which increased in intensity with the addition of Ga 2S 3. These are associated with the vibration of Ge–Ge bonds and edge-shared GaS 4 tetrahedra, respectively. Upon the addition of La 2S 3 into GeS 2–Ga 2S 3 glasses, intensities of these two bands decreased while a new band appeared at 375 cm −1 due to the vibration of tetrahedra with non-bridging sulfur(s). Dissociation of Ge–Ge bonds and edge-shared GaS 4 tetrahedra through the addition of La 2S 3 are responsible for the non-bridging sulfur formation. La 3+ can be dissolved into the glass network as charge compensators for these non-bridging sulfurs. Since no such structural unit is present in glasses without Ga 2S 3, this connection scheme and the structural modification in Ga-containing chalcogenide glasses seem to be crucial for an increase of La 3+ solubility.

The effect of compositional variations on the properties of rare-earth doped GeSI chalcohalide glasses

Undoped and Pr 3+-doped Ge x S y I z glasses, with atomic concentrations of germanium 0.33 ≤ x ≤ 0.43 and iodine 0 ≤ z ≤ 20, respectively, were synthesized and their optical and thermal properties measured. The properties followed the same compositional trends as the binary Ge x S 1 - x glasses, for which 0.33 ≤ x ≤ 0.43. The compositional dependences of the absorption edge and rare-earth solubility in Ge x S y I z glasses can be presented with a single parameter p = (y + z 2 ) x . Addition of iodine to the Ge-rich Ge x S 1 - x -base glass system resulted in increasing the optical bandgap energy and decreasing the glass transition temperature. Thermal stability of the Ge x S y I z glasses is a function of both S Ge ratio and iodine concentration. XPS and Raman spectroscopic measurements were conducted to obtain information about the structural changes accompanying the compositional variations. Properties-structure correlations are discussed. The results of the present study were used for selection of a compositional range within the Ge x S y I z glass system with optimal properties required for Pr 3+-doped fiber amplifier application.

Halide-modified Ga–La sulfide glasses with improved fiber-drawing and optical properties for Pr3+-doped fiber amplifiers at 1.3 μm

We report Cs halide-modified Ga–La sulfide glasses, a new class of chalcohalide glasses with improved fiber-drawing and optical properties suitable for Pr3+-doped fiber amplifiers at 1.3 μm. Cs halide-modified Ga–La sulfide glasses retain the essential characteristics of low phonon-energy and good rare-earth solubility of pure Ga–La sulfide glasses. However, they transmit further into the UV/visible region of the spectrum, and can meet the need of high thermal stability for fiber fabrication.

Solid solubility metastable extension of rare earth metals in gold

Metastable extended solid solubility of rare earth (RE) metals in gold was studied by measuring the lattice parameters of solid solutions of rapidly solidified Au-RE alloys using X-ray diffraction. The cooling rate used for the preparation of the alloys was about 106 K/s. It was found that the metastable solid solubilities of Ce, Sm, Gd, Dy, Er, Yb and Y in gold were 0.3, 0.4, 1.5, 9.0, 13, 13.4 and 10 atrespectively. The solid solubilities of RE metals in gold increased with decreasing relative difference of atomic radius between the RE metal and gold. The extended solid solubilities of RE metals in Au, Ag, and Cu were compared. The relatively large solid solubility in gold is explained in terms of electron transfer from the RE atoms to gold atoms. Under the conditions of rapid solidification, the Au-RE alloys tended to form amorphous alloys more readily than do Ag-RE alloys.

Fabrication of Er Doped Glass Films as Used in Planar Optical Waveguides

AbstractSilica integrated optical circuits are expanding in functionality to include optically active waveguides. Traditionally, the planar optical waveguide structures include silica based glass films such as thermal oxides, phosphorous, and boron-phosphorous doped glasses. Various efforts have successfully doped conventional waveguides with Er, typically by solution doping. Material issues such as rare earth solubility and glass structure dictate that efficient optical amplifiers based on such waveguides have path lengths in excess of 10–15 cm. We have developed an alternative strategy using Er-doped soda-lime silicate glass films on silicon. The waveguide processing utilizes methods of deposition similar to those used in silicon IC technology, with modificatons in the compositions and thicknesses. In these glasses the effective solubility limits are relaxed and we have successfully fabricated short path length devices which demonstrate net gain of more than 4 dB/cm. Short path length devices offer a potential advantage in highly integrated multi-channel devices and offer an additional building block in system architectures.

The aqueous geochemistry of the rare-earth elements and yttrium 4. Monazite solubility and REE mobility in exhalative massive sulfide-depositing environments

Although there is considerable evidence that rare-earth elements (REE), and particularly the light REE (LREE), have been mobile in the alteration zones below many massive sulfide deposits, there is some disagreement over the cause of this mobility. Most researchers have argued or implied that the REE were mobilized by analogues of modern seafloor hydrothermal vent fluids. However, the few measurements that have been made of the REE concentrations of these modern fluids suggest that their ability to mobilize REE is negligible. In order to shed further light on this problem we have carried out calculations of monazite solubility (monazite is thought to be the principal host for the LREE) in a model vent fluid at temperatures from 200° to 300°C. These calculations show that at 300°C the model fluid will contain 0.08 ppb Ce, 0.07 ppb La and 0.03 ppb Nd. At 200°C the concentrations increase to 0.54 ppb, 0.37 ppb and 0.15 ppb, respectively. A decrease in pH of one unit at 300°C also increases REE solubility significantly (7.4 ppb Ce, 5.7 ppb La and 1.1 ppb Nd). These solubilities are similar to the concentrations of REE measured in seafloor hydrothermal vent fluids. However, they are considerably lower than required to account for the scale of REE mobility in alteration zones associated with massive sulfide deposits. If the mass ratio of typical hydrothermal vent fluid to rock reached 1000, concentrations of REE in the altered rock the predicted to be in the range < 1 ppm to several ppm, whereas REE depletions up to several tens of ppm and enrichments in excess of 1000 ppm have been reported. Our calculations thus suggest that ancient analogues of modern seafloor hydrothermal vent fluids could not have transported REE in the quantities required to explain the extent of REE mobility documented for alteration zones associated with massive sulfide deposits. This finding requires that either ancient massive sulfide-forming hydrothermal systems were different in some critical respect from modern seafloor hydrothermal systems or that REE enrichment/depletion occurred during later metamorphism or alteration of massive sulfide deposits.

Implantation Doping and Stimulated Emission of Er3+ in LinbO3:Ti Optical Waveguides

AbstractWe have implanted Nd and Er ions into x- and z-cut LiNbC3 single crystals and investigated the recrystallization of the host and the rare earth solubility and diffusion. The diffusion is substitutional, fastest parallel to c-axis and characterized by an activation energy of 3.6 eV. Optical fluorescence experiments of Er3+ in a waveguide configuration show stimulated emission and amplification at 1.53, 1.55 and 1.56 μm wavelength.

Solid solubility of rare earths in aluminium

Monocrystalline and polycrystalline samples of Al:R ( R = Y, Gd, Tb, Dy, Er, Ho) were prepared by arc and levitation melting and the Czochralski method from the levitated melt. It follows from the electrical and magnetic measurements as well as the X-ray examinations that the equilibrium solid solubility is less than 100 ppm. The residual resistivity has a maximum at about 150 ppm and then decreases dramatically with increasing concentration. This is explained by nucleation of the RAl 3 phase.