Lanthanide solid state

Mixed valence in lanthanide solid state physics... 

For the observation of sharp and well-defined final-state configurations one is concerned with two problems (i) the need of sharp core levels, and (ii) the need of final-state configurations, which can be related to the unexcited ground-state configuration in a straightforward manner. In this paragraph we treat these two issues, discussing the choice of the most appropriate core holes for X-ray absorption spectroscopy as a tool in lanthanide solid state research. 

X-ray absorption spectroscopy in lanthanide solid state physics is used predominantly for the identification of atomic configurations which appear as atomic final-state multiplets (in Mjyy, N,v,v absorption) or atomic-like line spectra (in M Linii absorption). The configurations are identified from a distribution of intensities... 

Solid-State Lasers. Sohd-state lasers (37) use glassy or crystalline host materials containing some active species. The term soHd-state as used in connection with lasers does not imply semiconductors rather it appHes to soHd materials containing impurity ions. The impurity ions are typically ions of the transition metals, such as chromium, or ions of the rare-earth series, such as neodymium (see Lanthanides). Most often, the soHd material is in the form of a cylindrical rod with the ends poHshed flat and parallel, but a variety of other forms have been used, including slabs and cylindrical rods with the ends cut at Brewster s angle. 

Current availability of individual lanthanides (plus Y and La) in a state of high purity and relatively low cost has stimulated research into potential new applications. These are mainly in the field of solid state chemistry and include solid oxide fuel cells, new phosphors and perhaps most significantly high temperature superconductors... 

The chemistry of lanthanide nitridoborates was developed by the more flexible and more efficient solid-state metathesis route by using nitridoborate salts and a lanthanide trichloride, at reaction temperatures as low as 600 °C. This type of reaction has been previously established and studied in some detail for reactions, such as the synthesis of lanthanide nitrides (LnN). Following this concept, lanthanum nitridoborates are obtained from reactions of lanthanum trichloride and lithium nitridoborate (or calcium nitridoborate), performed in a salt-balanced manner with respect to the formation of the co-produced liCl ... 

In contrast, less is known about La-(CNx) compounds. The composition La2(CN2)3 was reported many years ago [43], without any structural information. Solid-state metathesis reactions of lanthanum chloride with Li2(CN2) or Zn(CN2) have recently brought up three series of the lanthanide compounds Ln2(CN2)3 [44], LnCl(CN2) [45], and Ln2Cl(CN2)N [46], Syntheses routes for Ln-(CNx) compounds containing new anions such as [C2N4] are to be developed, as well as for compounds in the La-B-C-N system (Fig. 8.15). 

The photochemical process will in general not occur in non-molecular solids due to the restriction in the nuclear coordinates. However, the nonradiative return to the ground state does, using MMCT states as an intermediary [35]. This can be nicely illustrated on a molecular solid, viz. the lanthanide-decatung-states which contain complex ions [Ln(III)Wio036] [40, 121]. 

Although the number of actinides is the same as that of the lanthanides, their availability and chemical characteristics have so far largely restricted the study of their ligand substitution mechanisms to dioxouranium(VI), which is the ionic form of uranium most amenable to such studies in solution. In the solid state, the oxo ligands occupy axial sites above and below the U(VI) center, and four (328), five (329, 330), and six (331, 332) oxygen donor atoms have been reported to occupy equatorial positions. From a mechanistic point of view, this variability of the occupancy of the equatorial plane suggests the possibility of both d- and a-activated ligand substitution pro-... 

Local Structure of the Eu2+ Impurity. From the experimental perspective, the doping of lanthanide ions into solid state materials can be probed by different instrumental technics such as nuclear magnetic resonance (NMR),44 extended X-ray absorption fine structure (EXAFS),45,46 or electron paramagnetic resonance (EPR),47 which instead of giving a direct clue of the local geometry offers only data that can be corroborated to it. From the theoretical point of view,... 

Qi M-H, Liu G-F (2004) Synthesis and photoelectronic properties on a series of lanthanide dysprosium(III) complexes with acetylacetonate and meso-tetraalkyltetrabenzoporphyrin. Solid State Sci 6(3) 287-294... 

In addition to X-ray crystallographic studies, two-dimensional NMR solution experiments (i.e., COSY, 1D-NOE, and NOESY, discussed in Sections 3.5.9 and 3.5.10) have been carried out on many lanthanide(III), Ln(ffl), chelate complexes to confirm that the structure of the MRI imaging agent, used in aqueous solution, will correspond to the solid-state X-ray crystallographic structure. Two-dimensional exchange spectroscopy (2D-EXSY) has been applied to lanthanide chelates to study the dynamics of conformational equilibria (how acetate arms chelate and how... 

EXAFS study on Eu2+ and Sr2+ in both solid state and aqueous solution gave coordination numbers of 8.0 for strontium(II) and 7.2 for europium(II) (228). The water exchange rate measured on the divalent europium aqua ion is the fastest ever measured by 170 NMR (Table XVI) (2). The activation volume is much more negative (—11.7 cm3 mol-1) than those determined on trivalent lanthanide aqua ions clearly indicating an a-activation mechanism which is most probably a limiting... 

III, F. More phase diagrams of complex fluorides have been explored using Knudsen cell mass spectrometry (13, 15), and electron impact studies have yielded enthalpies and bond energies (1,3). The heat of formation of MoFmi) has been confirmed (12). Solid state cells have been used with lanthanide trifluorides (24) and NaNiF3 (21). 

Other uranium binary systems de-mixing in the liquid state are U-Pb and U-Bi and several uranium-lanthanides systems which are characterized by nearly complete immiscibility in the liquid and solid state. 

The i>c=0 of the complexes of PA with lanthanides occurs at 1662 cm-1 and does not show a shift from the free ligand value in the solid state (59). The small shift in i>c=o 1S due to the fact that the C=0 group of the free ligand is involved in hydrogen bonding in the solid state. However, in acetonitrile solution, the hydrogen bonds break and the i>c==0 °f the pure ligand appears at 1690 1. This value indicates a shift of 30 cm-1 in the vc=o of the complexes. 

Misch metal, an alloy of cerium with other lanthanides is a pyrophoric substance and is used to make gas lighters and ignition devices. Some other applications of the metal or its alloys are in solid state devices rocket propellant compositions as getter in vacuum tubes and as a diluent for plutonium in nuclear fuel. 

As seen in the first chapter, the study of the solid state properties of actinides and their compounds is advancing rapidly, since theoretical and experimental solid state physicists are increasingly interested in the pecuUar behaviour of 5f electrons, which cause solid state properties similar to those of d transition elements in the first half of the series and to those of 4f lanthanides in the second half ... 

Jones, P. L. Amoroso, A. J. Jeffery, J. C. McCleverty, J. A. Psillakis, E. Rees, L. H. Ward, M. D. Lanthanide complexes of the hexadentate N-donor podand tris [3-(2-pyri-dyl)pyrazolyl] hydro ) rate solid-state and solution properties. Inorg. Chem. 1997, 36(1), 10-18. 

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