13765-26-9Relevant articles and documents
The phase diagram of the system LiF-GdF3
Ranieri,Bressiani,Morato,Baldochi
, p. 95 - 98 (2004)
The phase diagram of the system LiF-GdF3 has been revised, using differential thermal analysis (DTA). We observed a eutectic reaction at 25mol% of GdF3 and 698°C and a peritectic reaction at 34mol% of GdF 3 and 755°C. We found indications for a GdF3 phase transformation from hexagonal to orthorhombic at 900°C. An identification of the formed phases was made by X-ray diffraction and SEM.
High Purity Gadolinium by the Electrolysis of GdF3
Zwilling, Gunter
, p. 157 - 166 (1981)
The anodic overvoltage on carbon and platinum electrodes in the electrochemical production of high purity gadolinium from molten 75 LiF-25 molpercent GdF3 solutions is discussed.At the cell temperature of 840 deg C calciumimpregnated anodes led to the reduction of inert electrode films and to a current yield of nearly 100percent.The deposited gadolinium contained 75, 22, 54 and less than 100 ppm of the interstitial elements H, N, O and C respectively; the concentrations of the highest other analysed impurities were : Si(89), Fe(15), Y(5), Zr(3), Nd(3), Tb(71), Ta(49), W(23) and R e( 3 ppm). - Keywords: Electrolysis of gadolinium fluoride; Fluorine overpotentials; Gadolinium, high purity
Variation in Eu3+ luminescence properties of GdF 3:Eu3+ nanophosphors depending on matrix GdF3 polytype
Zhang, Xiaoting,Hayakawa, Tomokatsu,Nogami, Masayuki,Ishikawa, Yukari
, p. 2076 - 2080 (2011)
Hexagonal and orthorhombic GdF3:Eu3+ nanophosphors separately synthesized at room temperature were well characterized by X-ray diffraction (XRD) analysis and photoluminescence excitation and emission spectral measurements. Hexagonal GdF3:Eu3+ nanophosphors intrinsically exhibited stronger Eu3+ luminescence intensity under ultraviolet excitation. The Rietveld fitting of well-defined XRD data elucidated that the interatomic distances between Gd3+ ions in the hexagonal structure were shorter than those in the orthorhombic structure and that most Eu ions in GdF3:Eu3+ occupy Gd sites. The stronger luminescence in the hexagonal structure was conclusively explained by the much more efficient energy transfer from Gd to Eu in the hexagonal structure than in the orthorhombic structure, as determined on the basis of the interatomic distance between Gd and Eu.
The phase diagram GdF3-LuF3
Ranieri,Baldochi,Klimm
, p. 1070 - 1074 (2008)
The phase diagram gadolinium fluoride-lutetium fluoride was determined by differential scanning calorimetry (DSC) and X-ray powder diffraction analysis. Both pure components undergo a reversible first order transformation to a high temperature phase. The mutual solubility of both components is unlimited in the orthorhombic room temperature phase. The maximum solubility of Lu in the high temperature phase of GdF3 (tysonite type) is about 20% and the maximum solubility of Gd in LuF3 (α-YF3 type) is about 40%. Intermediate compositions of the low temperature phase decompose upon heating in a peritectoid reaction to a mixture of both high temperature phases.
Comparison of different NaGdF4:Eu3+ synthesis routes and their influence on its structural and luminescent properties
Karbowiak, Miros?aw,Mech, Agnieszka,Bednarkiewicz, Artur,Str?k, Wies?aw,K?piński, Leszek
, p. 1008 - 1019 (2005)
Eu3+:NaGdF4 samples were obtained via co-precipitation in aqueous solution (CP), reversed micelle (RM) method, reaction between solid GdF3 and NaF solution (SR) as well as a solid-state reaction at high temperatures (SS). The synthesised materials were characterised using X-ray powder diffractometry, TEM microscopy, infrared spectroscopy and TGA analysis. For discussion of optical properties excitation and emission spectra were recorded and emission decay times were measured. The CP and RM methods allow to obtain powders with crystallite size of ～10 nm, which may be smoothly increased to about 1 μm during post-fabrication heat treatment. Differences in structural and especially in optical properties of phosphors prepared by different techniques are emphasised and applicability of wet-chemistry routes for synthesis of fluoride powders is argued.
Self-assembled β-NaGdF4 microcrystals: Hydrothermal synthesis, morphology evolution, and luminescence properties
He, Fei,Yang, Piaoping,Wang, Dong,Niu, Na,Gai, Shili,Li, Xingbo
, p. 4116 - 4124 (2011)
A self-assembly process has been designed for the controlled synthesis of β-NaGdF4 with uniform morphology, dimension, and considerable monodispersity under a gentle hydrothermal condition using sodium citrate as the chelating agent. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrum (EDS), and up-conversion (UC) photoluminescence spectra were used to characterize the samples. The results indicate that the NaGdF4 microcrystal can be rationally modified in phase, size, and morphology through tuning the pH value, sodium citrate content, and reaction time. Moreover, the hybrid process of the crystal growth and the self-assembly were thoroughly discussed, and a possible formation mechanism was proposed. Furthermore, the UC luminescence properties as well as the emission mechanisms of β-NaGdF4:17%Yb3+/3%Ln 3+ (Ln = Er, Tm, Ho) microcrystals were systematically investigated. It is found that under 980 nm excitation, only limited emission bands were discovered which can be attributed to the energy gap and migration function of the Gd3+ ions in the β-NaGdF4 microcrystals. It is expected that the synthetic strategy can be applied to prepare many other types of micro- and nanocrystals as well.
Phase transitions and thermal properties of gadolinium trifluoride
Stankus,Khairulin,Lyapunov
, p. 30 - 33 (1999)
The temperature dependence of gadolinium trifluoride density in the solid and liquid states was determined by a gamma attenuation technique. Volume changes on solid-solid and liquid-liquid transitions were measured. The density and volume coefficient of thermal expansion of the liquid salt at the melting point are equal to 5609±25 kg m-3 and (16.2±0.5)×10-5 K-1, respectively. The relative density reduction on melting equals 16.7±0.15%. The polymorphic transformation from the low-temperature orthorhombic modification (a lattice of β-YF3 type) into the high-temperature hexagonal phase (LaF3 type) occurs with an increase of the density (about 2.1%). The peculiarities of the thermal expansion of the solid rare earth fluorides, undergoing phase transition β-YF3-type→LaF3-type, are discussed.
Lanthanide pentafluorophenolates. Synthesis, structure and luminescent properties
Maleev, Alexander A.,Fagin, Anatoly A.,Ilichev, Vasily A.,Lopatin, Mikhail A.,Konev, Alexey N.,Samsonov, Maksim A.,Fukin, Georgy K.,Bochkarev, Mikhail N.
, p. 126 - 132 (2013/11/19)
The pentafluorophenolates of lanthanides Ln(OC6F 5)3 (Ln = Nd (1), Tb (2), Er (3)) were prepared by the reactions of pentafluorophenol with appropriate silylamides Ln[N(SiMe 3)2]3 in benzene or toluene solution. The same reactions in ether or methanol medium afforded the solvated complexes Ln(OC 6F5)3(Et2O)3 (Ln = Nd (4), Eu (5), Tb (6), Er (7), Gd (8)) or Nd(OC6F5) 3(MeOH)3 (9), respectively. The phenanthroline complexes Ln(C6F5O)3(phen) (Ln = Pr (10), Nd (11), Er (12)), Ln(OC6F5)3(phen)2 (Ln = Sm (13), Tb (14), Ho (15), Ln(OC6F5)3(phen) 2(Et2O) (Ln = Eu (16), Yb (17)), and Ln(OC 6F5)3(phen)(Et2O)3 (Ln = Eu (18), Nd (19), Ce (20), Dy (21)), Ln(OC6F5) 3(phen)2(H2O) (Ln = Sm (22), Ho (23)), and Gd(OC6F5)3(phen)2(MeOH) (24) were obtained when the reactions were carried out in the presence of 1,10-phenanthroline. The complexes with pyridine Tb(OC6F 5)3(py)5 (25) and 2,2′-bipyridyl Ln(OC6F5)3(bpy)2 (Ln = Tb (26), Yb (27)) were synthesized similarly. Compounds 7, 22, 23, and 24 were characterized by X-ray analysis. The complexes Ln(OC6F5)3 decompose above 150 C in vacuum to give lanthanide fluorides and octofluorodibenzo-p-dioxine. Phenanthroline derivatives are stable up to 310 C. Luminescence spectra of all the obtained complexes in visible region contain a broad band of ligand-centered emission peaked at 405-415 nm. Spectra of samarium 13, europium 5, 16, 18 and terbium 14, 25, 26 derivatives display also the characteristic narrow bands of Sm3+, Eu3+ and Tb 3+ ions.
The new carbodiimide Li2Gd2Sr(CN2) 5 having a crystal structure related to that of Gd 2(CN2)3
Unverfehrt, Leonid,Stroebele, Markus,Meyer, H.-Juergen
, p. 84 - 88 (2013/03/28)
The new carbodiimide compounds Li2RE2Sr(CN 2)5 (RE = Sm, Gd, Eu, Tb) were prepared by a straight forward solid state metathesis reaction of REF3, SrF2, and Li2(CN2) at around 600 °C. The crystal structure of Li2Gd2Sr(CN2)5 was solved based on X-ray single-crystal diffraction data. Corresponding Li2RE 2Sr(CN2)5 compounds were analyzed by isotypic indexing of their powder patterns. The crystal structure of Li 2Gd2Sr(CN2)5 can be well related to that of Gd2(CN2)3, because both structures are based on layered structures composed of close packed layers of [N=C=N] 2- sticks, alternating with layers of metal ions. The crystal structure of Li2Gd2Sr(CN2)5 can be considered to contain an ABC layer sequence of [N = C=N]2- layers with the interlayer voids being occupied by (three) distinct types of cations. Copyright
Infrared spectra and quantum chemical calculations of the bridge-bonded HC(F)LnF2 (Ln = La-Lu) complexes
Gong, Yu,Wang, Xuefeng,Andrews, Lester,Chen, Mingyang,Dixon, David A.
, p. 4443 - 4452 (2011/10/10)
Lanthanide metal atoms, produced by laser ablation, were condensed with CHF3 (CDF3) in excess argon or neon at 4 K, and new infrared absorptions are assigned to the oxidative addition product fluoromethylene lanthanide difluoride complex on the basis of deuterium substitution and density functional theory frequency calculations. Two dominant bands in the 500 cm-1 region are identified as metal-fluorine stretching modes. A band in the mid-600 cm-1 region is diagnostic for the unusual fluorine bridge bond C-(F)-Ln. Our calculations show that most of the bridged HC(F)LnF2 structures are 3-6 kcal/mol lower in energy than the open CHF-LnF2 structures, which is in contrast to the open structures observed for the corresponding CH2-LnF2 methylene lanthanide difluorides. Argon-to-neon matrix shifts are 15-16 cm -1 to the blue for stretching of the almost purely ionic Ln-F bonds, as expected, but 10 cm-1 to the red for the bridge C-(F)-Ln stretching mode, which arises because Ar binds more strongly to the electropositive Ln center, decreasing the bridge bonding, and thus allowing a higher C-F stretching frequency.
