Search results for "Ionic radius"
showing 10 items of 29 documents
Mössbauer effect study of the electronic ground state of iron(II) in [57FexM1−x(bipy)3](ClO4)2 (M = Mn, Ni, Zn) and [57FexM1−x(phen)3](ClO4)2 (M = Ni…
1980
Earlier work in our laboratory on the effect of metal dilution on the 5T2(Oh ⇌ 1A1(Oh) equilibrium in polycrystalline spin crossover systems of iron(II) has shown that the relative stability of the high spin state, 5T2(Oh), at a given temperature, increases markedly with decreasing iron concentration. These results have initiated the present work. Using 57Fe Mossbauer spectroscopy, we have investigated the electronic ground state of iron(II) in the highly diluted solid solutions [FexM1−xL3] with L = bipy, M = Mn, Ni, Zn, x ≲ 0.005 and L = phen, M = Ni, Zn, x ≲ 0.005. Although the critical field potential (Vc) of the pure iron complexes, which are known to be low spin, is reported to be not …
Mobility of the Singly-Charged Lanthanide and Actinide Cations: Trends and Perspectives
2020
The current status of gaseous transport studies of the singly-charged lanthanide and actinide ions is reviewed in light of potential applications to superheavy ions. The measurements and calculations for the mobility of lanthanide ions in He and Ar agree well, and they are remarkably sensitive to the electronic configuration of the ion, namely, whether the outer electronic shells are 6s, 5d6s or 6s$^2$. The previous theoretical work is extended here to ions of the actinide family with zero electron orbital momentum: Ac$^+$ (7s$^2$, $^1$S), Am$^+$ (5f$^7$7s $^9$S$^\circ$), Cm$^+$ (5f$^7$7s$^2$ $^8$S$^\circ$), No$^+$ (5f$^{14}$7s $^2$S) and Lr$^+$ (5f$^{14}$7s$^2$ $^1$S). The calculations rev…
Limiting transport properties of lanthanide and actinide ions in pure water
2003
Summary The limiting transport properties, i.e. the limiting ionic conductivity (λ°) and the limiting diffusion coefficient (D°), of lanthanide and actinide ions at 298.15K have been calculated by means of the microscopic version of the Stokes–Einstein law involving (i) the effective charge and the ionic radius of the ions and (ii) the ion micro-viscosity, i.e. the viscosity of the hydrated water molecules in the vicinity of the ion. The latter quantity was derived from the variation of the dynamic properties of the water molecules in the first hydration shell with the surface charge density of common mono-atomic cations of various charges. The obtained results were found to be consistent w…
Selective Lanthanides Sequestration Based on a Self-Assembled Organosilica
2010
International audience; In this paper, we investigate the cation-exchange properties of a self-assembled hybrid material towards trivalent ions, lanthanides (La3+,Eu3+, Gd3+,Yb3+) and Fe3+. The bis-zwitter- ionic lamellar material was prepared by sol-gel process from only 3-amino- propyltriethoxysilane (APTES), succin- ic anhydride, and ethylenediamine. In ethanol heated under reflux, the ex- change ethylenediammonium versus Ln3+ proved to be complete by com- plexometry measurements and elemen- tal analyses, one Cl ion per one LnIII remaining as expected for charge bal- ance. In aqueous solution at 20 8C, the material was found to be selective to- wards lanthanide in spite of the similar- i…
The behaviour of zirconium and hafnium during water-rock interaction
2018
Abstract Zr and Hf are two elements with same ionic charge and similar ionic size at a given coordination number. Despite the Zr/Hf ratio is quite constant in meteorites and lithospheric rocks, in natural waters can be either higher or lower compared to values of interacting minerals and rocks. Here, we reanalyze very recent published and present new data on continental and brine waters indicating that the Zr and Hf behavior is dependent on the properties of the authigenic phases formed during the water-rock interaction process. Our results show that water pH in the range between 1 and 9 and water ionic strength in the range between 0.001 and 4 mol kg−1 are responsible for the change of the…
<title>Optical characteristics of doped lithium niobate single crystals</title>
2003
Studing of the Raman spectra was established that an optical parameters of oxygen-polyhedral ferroelectric single crystals can be improved by increasing the degree of structural ordering of the cation sublattice along the polar axis by doping them. In this case the impurity ions with the ionic radii close to the radii of the main cations (Li+ and Nb5+) and charges intermediate between those of main cations (1<Z<5) in the area of rather low concentrations were shown to exert an ordering effect on the cation sublattice of a congruent lithium niobate single crystals. Moreover the crystal resistance to laser radiation is also observed to grow. It was determined that the effect of diminishing ph…
Dopants and defects: local structure and dynamics in barium cerates and zirconates
2010
In this paper we present an overview of state-of-the-art EXAFS measurements and data analysis on Ba, Ce, Zr, Y, In and Gd local environments in Y:BaCeO3, In:BaCeO3, Gd:BaCeO3, Y:BaZrO3, and In:BaZrO3, at different temperatures, hydration degrees and doping levels. This approach allows to reach unprecedented insights on the peculiar role of the dopant, and its interactions with the other lattice defects. In particular, we evidence that each different dopant shows unique behavior, depending mainly on its electronic structure, and that the usual criterion of ionic radius matching is not useful to outline an effective doping strategy of proton-conducting perovskites. As what concerns the struct…
Impact of point defects on the elastic properties of BaZrO3: Comprehensive insight from experiments and ab initio calculations
2018
Abstract Acceptor doped BaZrO3 is the prototype of proton conducting perovskites which are of strong interest as electrolytes for intermediate temperature fuel cells. Elastic properties of both dry and hydrated Y-doped BaZrO3 (1.5–17 mol% Y) were determined using ultrasound time of flight (TOF) measurements, and complemented by ab initio calculations which allow for an analysis of the different contributions. The experimental and theoretical findings are consistent and reveal a strong decrease of the Young's, shear and bulk moduli upon increasing dopant concentration. This decrease is attributed to a combined effect of (i) macroscopic lattice chemical expansion mainly caused by differing io…
Stability of the fergusonite phase in GdNbO 4 by high pressure XRD and Raman experiments
2017
Abstract We describe the results of high pressure x-ray diffraction and Raman measurements on gadolinium orthoniobate. The ambient pressure monoclinic fergusonite phase remains stable in a remarkable large pressure range. There is no significative evolution of the monoclinic distortion up to 25 GPa , the maximum pressure achieved. Instead, the anisotropic compressibility is associated to the stiffness of NbO 4 tetrahedra in respect to the GdO 8 polyhedra. The high pressure evolution of external modes parallels the wavenumber dependence on ionic radius along the lanthanide series. The chemical pressure analogy is attributed to the compression of GdO 8 polyhedra. There is no evidence of any p…
Synthesis, structure and spectroscopic properties of luminescent GdVO 4 :Dy 3+ and DyVO 4 particles
2018
Part of this research was done during visit of D.J. to IFN-CNR CSMFO Lab. and FBK Photonics Unit, Povo-Trento, Italy, in the framework of the STSM (Grant No. 38223) from the project: COST Action MP 1401 Advanced Fibre Laser and Coherent Source as tools for Society, Manufacturing and Lifescience” (2014e2018). The authors from Vinca Institute of Nuclear Sciences acknowledge the financial support of the Ministry of Education, Science and Tech-nological Development of the Republic of Serbia (Project No: 45020 and 172056). L.T.N. Tran acknowledges the scholarship of the Ministry of Education and Training, Vietnam International Education Development. T. G. acknowledges the ERDF PostDoc project No…