Influence of structure and lonic radius on solubility limit in the Mg-Re systems

The relationship between structure, ionic radius and electronegativity and solubility of the various rare-earth elements in Mg was studied. It is found that light RE(La-Sm, Eu, Yb) have more complicated phase relation with Mg but the heavy RE(Gd-Lu, Sc) have the similar crystal structure with magnesium. Also it is found that the less electronegativity difference between Mg and RE is, the more solubility limit of RE in Mg is. The fact of the RE solubility decreased in magnesium with lowering temperature suggests that there is a possibility of Mg supersaturated solid solution formation and it will decomposition during aging. According to the rule, an megnesium alloy with higher strength feature was developed. Their mechanical properties are UTS 347MPa, YTS 290MPa and elongation 12.5% at room temperature.

Fabrication and luminescent properties of rare earths-doped Gd-2(WO4)(3) thin film phosphors by Pechini sol-gel process

Rare earth ions (Eu3+ and Dy3+)-doped Gd-2(WO4)(3) phosphor films were prepared by a Pechini sol-gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM) and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting powders and films. The results of XRD indicate that the films begin to crystallize at 600degreesC and the crystallinity increases with the elevation of annealing temperatures. The film is uniform and crack-free, WO(4)(2-)mainly consists of closely packed fine particles with an average grain size of 80 nm. Owing to an energy transfer from 4 groups, the rare earth ions show their characteristic emissions in crystalline Gd-2(WO4)(3) phosphor films, i.e., D-5(J) -F-7(J), (J = 0, 1, 2, 3; J' = 0 1, 2, 3, 4, not in all cases) transitions for Eu3+ and F-4(9/2)-H-6(J) (J = 13/2, 15/2) transitions for D Y3+, with the hypersensitive transitions D-5(0)-F-7(2) (Eu3+) and F-4(9/2) - H-6(13/2) (Dy3+) being the most prominent groups, respectively.

Structure and electrochemical characteristics of RENi3 alloy

The RENi3 (RE = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Y) series compounds have been prepared by arc melting constituent elements under Ar atmosphere. X-ray diffraction (XRD) analysis reveals that the as-prepared alloys have different lattice parameters and cell volumes, depending on different rare earth (RE) element. The electrochemical characteristics, including the electrochemical capacity, P-C isotherms, high rate chargeability (HRC) and high-rate dischargeability (HRD), of these alloys have been studied through the charge-discharge recycle testing at different temperatures, charge currents and discharge currents. The results show that YNi3 has the largest cell volume, smallest density, and moreover, it shows more satisfactory electrochemical characteristics than other alloys, including discharge capacity, HRC, HRD and low temperature dischargeablity.

Phase transition of BaNd2Mn2O7

Phase transition of BaNd2Mn2O7 from orthorhombic (space group Fmmm) to tetragonal phase (I4/mmm) was studied by high temperature powder X-ray diffractometry and Rietveld analysis. The transition temperature was identified at 523 K, which is almost the same transition temperature as the compounds with other rare earth ions in this BaLn(2)Mn(2)O(7) family (Ln=Sm and Eu) with Fmmm space group. During the transition an oxygen octahedron of each phase changes a little its form, in which four oxygen atoms perpendicular to C-axis make a rectangle and a square for orthorhombic and tetragonal phases, respectively. Manganese ion is not on the center of the quadrilateral consisting of these four oxygen ions, but a little apart from the center along c-axis in both phases.

Selective separation of yttrium by CA-100 in the presence of a complexing agent

The selective separation of Y from yttrium solution containing small heavy rare earth (HRE) impurities (Ho, Er, Tm, Yb, Lu) by liquid-liquid extraction using CA-100 in the presence of a water-soluble complexing agent of ethylenediaminetetraacetic acid (EDTA) was experimentally studied at 298K. Experiments were carried Out in two feeds, Feed-I: [RE](f) = 4.94 x 10(-3) M, Y = 98.5%, HRE (Ho, Er, Tm, Yb, Lu) = 1.5%; Feed-II: [RE](f) = 4.94 x 10(-3) M, Y = 99.9%, HRE (Ho, Er, Tm, Yb, Lu) = 0.1%, as a function of equilibrium pH (pH(eq)), the concentration ratio of [EDTA]:[HRE impurities]. It was shown that the extraction of HRE in the presence of EDTA was suppressed when compared to that of Y because of the masking effect, while the selective extraction of Y was enhanced and the separation factors increased to maximum at appropriate condition for Feed-I: Y/Ho = 1.53, Y/Er = 3.09, Y/Tm = 5.61, Y/Yb = 12.04, Y/Lu = 27.51 at pH 4.37 and [EDTA]:[HRE impurities] = 4: 1, for Feed-II: Y/Ho = 1.32, Y/Er = 1.91, Y/Tm = 2.00, Y/Yb = 3.05, Y/Lu = 3.33 at pH 4.42 and [EDTA]: [HRE impurities] = 8:1. The separation and purification of Y by this method was discussed.

Synergistic extraction of rare earths(III) from chloride medium with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazalone-5 and di-(2-ethylhexyl)-2-ethylhexylphosphonate

The synergistic effect of 1-phenyl-3-methyl-4-benzoyl-pyrazalone-5 (HPMBP, HA) and di-(2ethylhexyl)-2-ethylhexylphosphonate (DEHEHP, B) in the extraction of rare earths (RE) from chloride solutions has been investigated. Under the experimental conditions used, there was no detectable extraction when DEHEHP was used as a single extractant while the amount of RE(III) extracted by HPMBP alone was also low. But mixtures of the two extractants at a certain ratio had very high extractability for all the RE (III). For example, the synergistic enhancement coefficient was calculated to be 9.35 for Y3+, and taking Yb3+ and Y3+ as examples, RE3+ is extracted as RE(OH)A(2).B. The stoichiometry, extraction constants and thermodynamic functions such as Gibbs free energy change Delta G (-17.06kJmol(-1)), enthalpy change Delta H (-35.08kjmol(-1)) and entropy change Delta S (-60.47JK(-1)mol(-1)) for Y3+ at 298 K were determined. The separation factors (SF) for adjacent pairs of rare earths were calculated. Studies show that the binary extraction system not only enhances the extraction efficiency of RE(III) but also improves the selectivity, especially between La(III) and the other rare earth elements.

Luminescence of the compounds Y0.5-xLi1.5VO4 :(Dy3+,Eu3+)

In this paper for the first time the compounds Y0.5-xLi1.5VO4:(Dy3+, Eu3+),(YLV:Dy,Eu) (0.01rare earth vanadates. Their structures were analyzed by X-ray powder diffraction experiment. The excitation and emission spectra were measured at room temperature. The blue, the yellow and the red emission from the F-4(9/2)-H-6(15/2) (474.2-484.2 nm) transitions and F-4(9/2)-H-6(13/2) (568-576.4 nm) transitions of Dy3+ and the D-5(0)-F-7(2) (608-619.2 nm) transitions of Eu3+, respectively, are very strong in multiwavelength.

A novel way to enhance electroluminescence performance based on soluble binary and ternary europium 1,1,1-trifluoroacetylacetonate

Five rare earth complexes (Gd(acae)(3), Gd(TFacaC)(3), Eu(acaC)(3), Eu(TFacaC)(3) and Eu(TFacaC)(3)bipy; acac, acetylacetone; TFacac, 1,1,1-trifluoroacetylacetone; bipy, 2,2'-bipyridyl) were synthesized. By comparing the phosphorescence spectra of Gd(acac)(3) and Gd(TFacac)(3) the effect of the replacement of hydrogen by fluorine was examined. Organic light-emitting devices (OLEDs) based on the corresponding europium complexes as emissive layers were also fabricated by the spin-coating method. The triple-layer-type device with the structure glass substrate/ITO (indium-tin oxide)/PVK [poly(N-vinylcarbazole)]/(PVKEu)-Eu-.(TFacac)(3)bipy:PBD[2-(4-bibipyyl)-5-(4-t-butylbipyl-1,3,4-oxadiazole)]/PBD/Al (aluminum) exhibits a brighter red luminescence than those devices with Eu(acac)(3) and Eu(TFacac)(3) complexes as emissive centers upon applying a d.c. voltage.

Synthesis and luminescence properties of oxyapatite NaY9Si6O26 doped with Eu3+, Tb3+, Dy3+ and Pb2+

Oxyapatite NaY9Si6O26 was prepared by sol-gel method. By choosing the precursors, a single phase compound was obtained. This soft chemical method lowered the reaction temperature by 100degreesC compared with the solid state method. Its morphology was studied by transmission electron microscopy (TEM). Several rare earth ions (Eu3+, Tb3+, Dy3+) and Pb2+ ion were doped in this compound. The high resolution emission spectrum of Eu3+ showed that rare earth ions occupied two yttrium sites. In spite of the charge imbalance of Pb2+ with the cations in this compound, it was found that Pb2+ could emit in UV range and transfer its excitation energy to Dy3+ ion.

Synthesis, luminescence, energy transfer and Langmuir-Blodgett films of amphiphilic complexes of rare earths with monooctadecyl phthalate

Three new amphiphilic rare earth complexes with only two organic long chains Ln (MOP)(2)Cl (MOP=monooctadecyl phthalate, Ln=Eu, Tb, Gd) were synthesized and characterized by elemental analysis. The complexes (Eu, Tb) showed good luminescence property with long fluorescence lifetime, whereas the intensity and lifetime of Tb complex are greater than those of Eu complex, By measuring the triplet energy levels of ligand based on energy transfer mechanism, above phenomena have been well explained. The Langmuir films of the complexes on the air/water interface were also studied and the results show that all of them have good film-forming property.

pH-potentiometric study on rare earths and calcium binary and ternary complexes with DL-malic acid and L-hydroxyproline

The stability constants of M-L binary system and M-L-L' (M = La3+ similar to Yb3+, Y3+ and Ca2+; L= DL-malic aicd, L' = L-hydroxyproline) ternary system were determined by pH-(0)-tentiometric method under the simulating physiological condition(37 degrees C, I=0.15 mol/L NaCl). The complex species MpLqLr'H-s(abbr as pqrs) in the sytems were ascertained by program COMPLEX. The results show that there are three species(1101, 1100 and 1200) in M-L binary system and one species(1010) in M-L' binary system. In addition to the above four species, a new species, 1112 was found in the M-L-L' ternary system, which is the only species of mixed ligands. Rare earth ions form more stable complexes than calcium ion does and the stability differences between their complexes in the ternary system are less than that in the binary system. The distributions of all the species in La-L-L' ternary system vs pH are discussed.

The photophysical properties of binary and ternary complexes of rare earths with conjugated carboxylic acids and 1,10-phenanthroline

Results of photophysical properties of the complexes of Gd3+, Eu3+ and Tb3+ with conjugated carboxylic acids (3,4-funandicarboxylic acid and nicotinic acid) and 1,10-phenanthroline are reported. Whether between central ions and ligands or between the two ligands, it is found that the intramolecular energy efficiency is a sensitive function of the relative positions of the resonance energy levels of the central ions and the lowest triplet states of the ligands. Couplings of rare earth ions to the ligands are discussed in detail. (C) 1997 Elsevier Science S.A.

Relationship between the dissolution behaviours and current efficiencies of La, Ce, Pr and Nd in their chloride molten salts

The dissolution behaviours of La and Nd in their chloride molten salts were studied by means of the see-through cell, electrochemical weak polarization and quantum chemistry (extended Huckel molecular orbital). The reasons for the low current efficiencies of rare earth metals and the difference between La and Nd in their own chloride electrolytes on the basis of the solubility, rate of dissolution, and existing state of the metals dissolved as well as the structure of the melts, are discussed.

Preparation, structure and some physical properties of scheelite-related AgLnMo(2)O(8) compounds

We present the synthesis of the AgLnMo(2)O(8) oxides with Ln = La-Nd, Sm, Gd, Tb and Y. These compounds represent a scheelite-related structure type characterized by MoO42- tetrahedrons. The IR spectra show three transmittance bands in the region of 1000-400 cm(-1), which correspond respectively to the nu(1), nu(2), and nu(3) modes of the tetrahedral MoO42- groups. All of AgLnMo(2)O(8) are insulator materials at room temperature. The temperature dependence of the magnetic susceptibilities of AgLnMo(2)O(8) (Ln = Ce-Nd, Sm, Gd, Tb) show Curie-Weiss Law behaviors with two anomalies occurring at low temperature, whereas AgLaMo2O8 and AgYMo2O8 both exhibit diamagnetic properties as expected. The magnetic moments at room temperature fit very well with those corresponding to rare earth sesquioxides. This suggests that rare earth ions exist in +3 oxidation state in all AgLnMo(2)O(8) compounds.

X-RAY PHOTOELECTRON-SPECTRA OF SOME BIOINORGANIC COMPLEXES OF THE RARE-EARTHS WITH N-ACETYLALANINE

X-Ray photoelectron spectra of some bioinorganic complexes of La, Ce, PT, Nd, Sm and Eu with N-acetylalanine have been measured and the 3d5/2 and 3d3/2 main peaks and their satellites have also been assigned. ne spin-orbit splitting between the 3d5/2 and 3d3/2 core-level of the rare earth ion in these complexes becomes slightly larger than that of the free rare earth atom due to the effect of the crystal field. The satellite for the 3d main peaks of La in the solid state complex are in higher binding energy region and may be attributable to the L --> 4f charge-transfer shake-up process. The satellites for the 3d main peaks of Ce, Pr, Nd, Sm and Eu are in the lower binding energy region and may be attributable to the 4f --> L charge-transfer shake-down process.