- Lanthanide trifluoroacetate complexes with 2-azacyclononanone. Thermal and kinetic studies
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The synthesis and characterization of Lanthanide trifluoroacetate compounds by microanalytical procedures, infrared absorption spectroscopy, X ray powder diffraction and thermogravimetric analysis were discussed. A kinetic study using thermogravimetric curves obtained for La, Sm and Er was also carried out. The first and second derivatives reactions constituting thermal decomposition of the complexes indicated a high quality optimization of the mass curves. The decomposition occurred in five steps with similar activation energies and pre-exponential factors.
- Garrido Pedrosa,Pimentel,Araujo Melo,Scatena Jr.,Borges,Souza,Zinner
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- Polymorphism of Erbium Oxyfluoride: Selective Synthesis, Crystal Structure, and Phase-Dependent Upconversion Luminescence
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Phase-selective synthesis and structure switching behavior of a functional material are essential to enable comparative studies on the structure–property relationship. Here, we report a controllable fluorination route to phase-pure erbium oxyfluorides with orthorhombic (O-ErOF) and rhombohedral (R-ErOF) structures. This facile method adopts polytetrafluoroethylene (PTFE) as the fluoridizer, and the phase selectivity can be easily achieved at specific fluorination temperatures. The phase evolution and detailed crystal structures of erbium oxyfluoride were characterized by powder X-ray diffraction (PXRD) at various sintering temperatures and Rietveld refinements, respectively. An irreversible phase transition from O-ErOF to R-ErOF was observed under heating around 600 °C. The upconversion (UC) luminescence properties of R-ErOF and O-ErOF were studied comparatively by means of photoluminescence, P–I, and UC decay curves. Despite their similar components and crystal structure, R-ErOF exhibits stronger (more than 20 times) red UC emission than O-ErOF. The anomalous UC behavior of the two polymorphs of ErOF was associated with the energy transfer processes dependent on their crystal structure.
- Wen, Ting,Ding, Ruixian,Zhou, Yannan,Si, Yubing,Yang, Baocheng,Wang, Yonggang
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- Low temperature synthesis of LnOF rare-earth oxyfluorides through reaction of the oxides with PTFE
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A low temperature solid-state synthesis route, employing polytetrafluoroethylene (PTFE) and the rare-earth oxides, for the formation of the LnOF rare-earth oxyfluorides (Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er), is reported. With the exception of LaOF, which forms in a tetragonal variant, rhomobohedral LnOF is found to be the major product of the reaction. In the case of PrOF, a transition from the rhombohedral to the cubic fluorite phase is observed on heating in air to 500 °C. X-ray diffraction shows the expected lanthanide contraction in the lattice parameters and bond lengths. Magnetic susceptibility measurements show antiferromagnetic-like ordering in TbOF, Tm = 10 K, with a metamagnetic transition at a field μ0Ht = 1.8 T at 2 K. An antiferromagnetic transition, TN = 4 K, is observed in GdOF. Paramagnetic behavior is observed above 2 K in PrOF, NdOF, DyOF, HoOF and ErOF. The magnetic susceptibility of EuOF is characteristic of Van Vleck paramagnetism.
- Dutton,Hirai,Cava
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- Optically active uniform potassium and lithium rare earth fluoride nanocrystals derived from metal trifluroacetate precursors
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This paper reports the first systematical synthesis of near-monodisperse potassium and lithium rare earth (RE) fluoride (K(Li)REF4) nanocrystals with diverse shapes (cubic KLaF4 and KCeF4 wormlike nanowires, nanocubes and
- Du, Ya-Ping,Zhang, Ya-Wen,Sun, Ling-Dong,Yan, Chun-Hua
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p. 8574 - 8581
(2011/01/06)
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- Thermodynamics of the rhombohedral-cubic phase transition of ROF with R=Y, La, Pr, Nd, Sm-Er
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The temperatures and enthalpies of the rhombohedral-cubic phase transition of stoichiometric ROF with R=Y, La, Pr, Nd, Sm-Er, have been determined by differential scanning calorimetry. The temperatures of transition are found in the range 742-880 K in sat
- Petzel,Marx,Hormann
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