Local vibration around rare earth ions in alkaline earth fluorosilicate transparent glass and glass ceramics using Eu3+ probe

By heat treating the alkaline earth fluorosilicate glass, transparent glass ceramics containing alkaline earth fluoride nanocrystallites were prepared. The luminescence spectra and phonon sideband associated with the Eu3+:5D2→7F0 in glass and glass ceramics were investi-gated to analyze the local environment around Eu3+. Judd-Ofelt parameters were also calculated from emission spectra, which indicated that the Eu3+ ions entered the precipitated CaF2, SrF2, and BaF2 nanocrystallites. Heat treating could not pledge Eu3+ ions to coordinate with F in the precipitated MgF2 nanocrystallites, owing to the smaller radius of Mg2+ than that of Eu3+.     

Ultraviolet to visible frequency-conversion properties of rare earths doped glass ceramics

Nd3+,Eu3+ and Tb3+ ions doped transparent chlorophosphate glass ceramics were prepared and their frequency-conversion properties were studied. X-ray diffraction (XRD) patterns evidenced the formation of expected halide nanocrystals. The absorption,excitation and emission spectra investigation indicated that some of rare earth (RE) ions were trapped in low phonon energy halide nanocrystals,and therefore an efficient down frequency-conversion was observed. The comparative spectroscopic studies of RE doped samples suggested that the glass ceramics systems are potentially applicable as efficient ultraviolet to visible frequency-conversion photonics materials.     

Preparation and laser induced damage properties of rare earth doped BAS glass

Rare earth doped B2O3-Al2O3-SiO2 glass （RExBAS, x=5, 10, 20; RE=La, Sm） were prepared by solid state reaction method. Optical transmission spectra of such glass were characterized by ultraviolet spectrometers, and 1064 nm laser induced damage performance was investigated through the method of ＂1-on-1＂. The results indicated that there was a strong absorptive peak near 1064 nm in SmxBAS glass, the peak was enhanced with increasing x. While LaxBAS glass was transparent to 1064 nm laser, at the same time, the results of laser induced damage showed that the anti-laser induced damage performance of such glass was strengthened with the addition of rare earth oxide. Furthermore, the laser induced damage threshold （LIDT） of SmxBAS glass was significantly higher than that of LaxBAS glass. Consequently, Sm^3＋ doping was favor in the improvement of anti-laser induced damage performance for BAS glass.     

Preparation and luminescence properties of Ce3＋/Dy3＋-codoped fluorosilicate glass ceramics

The Ce3+and Dy3+ co-doped fluorosilicate glass and glass ceramics containing SrF2 or CeF3 nanocrystals were prepared under re-ducing atmosphere. The precipitated nano-crystalline phase shifted from cubic SrF2 to hexagonal CeF3 gradually with the heat treatment tem-perature increasing from 620 to 680 °C. The glass and glass ceramics emitted white light, deriving from a combination of the Ce3+ blue and the Dy3+ yellow light. The CIE coordinates could be tuned by adjusting the ratio of Ce3+/Dy3+ concentration. The luminescence could be en-hanced significantly by annealing the samples at the temperatures lower than 640 °C.     

Local structure and luminescent properties of lead phosphate glasses containing rare earth ions

Local structure and luminescent properties of lead phosphate glasses containing rare earth ions were studied.Optically active ions such as Eu3+,Dy3+,Tb3+ and Er3+ were chosen as dopants.The local structure was verified using X-ray diffraction and Fourier transform in-frared(FT-IR) spectroscopy.The visible luminescence bands recorded for the studied samples corresponded to 5D0→7FJ(J=0÷4) transitions of Eu3+,4F9/2→6HJ/2(J=11÷15) transitions of Dy3+,5D3→7FJ’(J’=1÷6) and 5D4-7FJ(J=3÷6) transitions of Tb3+,and 4S3/2→4I15/2 transitions of Er3+.     

A study on fluorescence properties of Eu3+ ions in alkali lead tellurofluoroborate glasses

Glasses with chemical composition of (in mol.%): 26 RF-20 PbO-10 TeO2-43 H3BO3-1 EuO3 (RLTB) were prepared by conventional melt quenching method. The Judd-Ofelt intensity parameters Ω2 and Ω6 were obtained from the absorption intensities of 7F0→5D2 and 7F0→5L6 transitions, respectively. In order to overcome the problem of applicability of Judd-Ofelt analysis at room temperature due to the overlapping of the transitions originating from 7F0 and 7F1 levels of Eu3+ ion, the effect of the thermalization on the population of energy levels was taken into account. The photoluminescence spectra contained five emission bands originating from the 5D0 metastable state to 7FJ (J=0, 1, 2, 3, 4) lower lying states. The decay profiles were found to be single exponential in all the three glasses. The measured lifetimes (τmes) were in good agreement with the calculated lifetimes (τcal) obtained by using the thermally corrected Judd-Ofelt intensity parameters.     

Local concentration of middle and heavy rare earth elements in the col on the weathered crust elution-deposited rare earth ores

This present study focused on investigating the content and relative enrichment multiple of rare earth elements(REEs) in different terrain of weathered ore body, and the value of light rare earth elements/middle and heavy rare earth elements(LREEs/HREEs), in order to understand the mobilization and redistribution of HREEs, Furthermore, the abrasion pH was investigated as well, The results show that the average contents of HREEs in the knap, ridge and col are 37.26, 61.71, and 271.3 μg/g, respectively. The value of LREEs/HREEs is decreased from 16.78 to 7.914 between knap and col and the relative enrichment multiple of HREEs is as follows: C_(Col-HREEs) C_(Ridge-HREEs) 0. It is indicated the HREEs is concentrated in the col and the enrichment degree of HREEs is stronger than the ridge and the knap. Rare earth elements fractionation is exhibited in the different terrain of weathered ore body. Based on this study, the finding that HREEs concentrate in the lower terrain of weathered crust elution-deposited rare earth ores, such as in the col, would become a marker or indicator to search for middle and heavy rare earth enriched zone.     

Properties of Local Structure Surrounding Eu3＋ Ion in Various Niobate-Silicate Glasses

A Series of niobate-silicate glasses doped with Eu3 ions were prepared. The emission, phonon-side band spectra, fluorescence line narrowing spectroscopy and fluorescence lifetimes in these glasses were studied. The intensity parameters and crystal field parameter of Eu3 were obtained. The results indicate that the intensity ratio of the electric-dipole to magnetic-dipole transition and the intensity parameter Ω2 increase with the increasing concentration of Nb2Os, indicating that the symmetry becomes lower, the Eu-O bonds become stronger and the covalency of Eu-O bond increases. The value of B20 decreases with the increasing concentration of Nb2O5, indicating that the distance between the Eu3 ion and oxygen decreases and the Eu-O bond becomes strong, corresponding to the results of the former. As the concentration of Nb2O5 increases, the electron-phonon coupling becomes stronger, thus the nonradiative transition rate of 5Do becomes larger and the lifetime of 5D0 becomes shorter.     

Ab initio calculation of electronic structures and 4f-5d transitions of some rare earth ions doped in crystal YPO4

The ab initio self-consistent DV-Xα (discrete variational Xα) method was used in its relativistic and spin-polarized model to investigate the ground-state electronic structures of the crystal YPO4 and YPO4:RE3 (RE=Ce, Pr and Sm) and f-d transition energies of the lattice. The calculation was performed on the clusters Y5P10O32 and REY4P10O32 embedded in a microcrystal containing about 1500 ions, respectively. The ground-state calculation provided the locations of the 4f and 5d crystal-field one-electron levels of RE3 relative to the valence and conduction bands of host, the curve of total and the partial density of states, and the corresponding occupation numbers, etc. Especially, the transition-state calculation was performed to obtain the 4f→5d transition energies of RE3 in comparison to the experimental observations. The lattice relaxation caused by the dopant ion RE3 was discussed based on the total energy calculation and the transition-state calculation of the f-d transition energies.     

Rate analysis of sorption of Ce3+, Sm3+, and Yb3+ ions from aqueous solution using Dowex 50W-X8 as a sorbent in a continuous flow reactor

Kinetic analysis of removal of three rare earth elements metals, Ce³⁺, Sm³⁺, and Yb³⁺ ions from aqueous solutions in a continuous flow fixed bed reactor using Dowex 50W-X8 ion-exchange resin was conducted. The performance of the fixed bed sorption was evaluated using the concept of the sorption breakthrough process. Parameters characteristic of a fixed bed sorption such as breakthrough times, saturation times, critical reactor lengths, and lengths of mass transfer zone were inferred from the metal ion concentration breakthrough curves. The sorption capacity of Dowex 50W-X8 ion-exchange resin for Ce³⁺, Sm³⁺, and Yb³⁺ are 191, 252, and 294 mg/g, respectively. The sorption kinetics were evaluated using a zero-order, first-order and second-order reaction models. The kinetics of the sorption process follows a zero-order model which has not been reported before. The rate constants of sorption using the zero-order kinetic model are obtained. Two different analysis were conducted to identify whether the diffusion is intraparticle or film diffusion. Both analysis confirms that the film diffusion is the controlling mechanism in reactor bed.     

Extraction of rare earth elements from their oxides using organophosphorus reagent complexes with HNO3 and H2O in supercritical CO2

Direct extraction of metals from solids with complexing agents in supercritical CO2(SC-CO2) has recently attracted interests in separation,purification,recovery,and analysis of metals.In the present study,the static/dynamic extraction of rare earth elements(Nd,Ce) from their oxides(Nd2O3,CeO2) with organophosphorus complexes with HNO3 and H2O in SC-CO2 was investigated.The static extraction efficiency of Nd from Nd2O3 with the tri-n-butylphosphate(TBP)-HNO3 complex could reach 95% under optimized experiment...     

Ab initio calculation of electronic structures and 4f-5d transitions of some rare earth ions doped in crystal YPO4

The ab initio self-consistent DV-X_α (discrete variational X_α) method was used in its relativistic and spin-polarized model to investigate the ground-state electronic structures of the crystal YPO₄ and YPO₄:RE³⁺ (RE=Ce, Pr and Sm) and f-d transition energies of the lattice. The calculation was performed on the clusters Y₅P₁₀O₃₂ and REY₄P₁₀O₃₂ embedded in a microcrystal containing about 1500 ions, respectively. The ground-state calculation provided the locations of the 4f and 5d crystal-field one-electron levels of RE³⁺ relative to the valence and conduction bands of host, the curve of total and the partial density of states, and the corresponding occupation numbers, etc. Especially, the transition-state calculation was performed to obtain the 4f → 5d transition energies of RE³⁺ in comparison to the experimental observations. The lattice relaxation caused by the dopant ion RE³⁺ was discussed based on the total energy calculation and the transition-state calculation of the f-d transition energies.