Europium compounds

Table I. Differences in Energy in Terms of Isomer Shift of the 21.7-k.e.v. Line of in Different Europium Compounds...

The enhancement of the fluorescent yield of terbium, europium, and gadolinium in heavy-water solutions was studied by Kropp and Windsor (105). They observed substantial increases in emission intensities for both terbium and europium compounds when ordinary water was replaced by deuterated water. No appreciable increase was observed for gadolinium, however. For terbium they also obtained the fluorescent lifetimes of the 5D4 state. 

Rieke and Allison (97) also examined the fluorescent-decay time of europium dibenzoylmethide (EuD3). They found a marked difference between it and unchelated europium compounds. The material was prepared by the method described by Crosby et al. (142). The data were collected by illuminating the samples with a stroboscopic light source of 20-/zsec decay time. The results for EuD3 as compared with their data on EuC13-4H20 are ... 

It was rather surprising when Hund and Durrwachter [312] found that La20s is miscible with TI1O2 to a great extent (52 mole per cent) whilst still preserving the cubic fluorite structure. The lattice constant of the mixed oxide has an a value 5.645 A compared to 5.592 A for TI1O2. The lattice constants of some orthorhombic perovskite and cubic garnet-type europium compounds are listed in Table 22. 

Table 22. Lattice constants of orthorhombic perovskite- and cubic garnet- type europium compounds...

The fluorescence properties of europium compounds offer another possibility for using them as a red component in colour television tubes. As all fluorescence compounds are not capable of producing laser action, they still stand a chance of being used as phosphors. Those phosphors which have a main emission peak between 6110 and 6140 A are the only ones suitable. The cathodoluminescence properties of several Eu3+ doped GdaOs and YVO4 proved to be highly efficient red emittors for colour... 

The readers will undoubtedly agree that the elucidations and derivations of the equations 13—15 are beyond the scope of this book, but chemists with some physical inclination may find some satisfaction in reading through Van Vleck s [207] Theory of Electric and Magnetic Susceptibilities to quench their mathemetical thirst. Instead of tabulating the measured magnetic moments of all europium compounds with variations we will mention the magnetic behaviour of the individual compounds as we deal with them. 

Table 48. The ratios of fluorescence intensities (rjDlrjHF and lifetimes (tdIth) in deuterated and nondevterated solvents of some europium compounds [607]...

Europium occurs in the rare-earth fluocarbonaie mineral basmasite. mainly found in southern California. The mineral contains between 0.09 and 0.11% EuiOi, Other minerals, such as xenolime and monazite. also contain europium compounds, and sometimes they are used as sources of he element. 

Of various rare earth 2-selenenoylacetone chelates luminescence was found only in the europium compounds. Physicochemical properties and IR spectra of 2-selenenoylacetonates of rare earths (except cerium and promethium) give information regarding the structure of these complexes as a function of the metal. 

Tridentate N-donor ligands are efficient in separating actinides from lanthanides selectively by solvent extraction, an area of potential great importance in treatment of used nuclear fuel rods. The tridentate ligand 2,2 6 ,2 -terpyridyl (terpy) forms a range of complexes. The perchlorate complexes [Ln(terpy)3] ( 104)3 contain nine-coordinate cations with near- )3 symmetry, a structure initially deduced from the fluorescence spectrum of the europium compound (Section 5.4) and subsequently confirmed by X-ray diffraction smdies (Figure 4.7)... 

The thermogravimetric curves of several europium compounds and tetracosane are shown in Figure 3. The thermograms of some of the tris rare earth thd chelates and the tetrakis zirconium compound are presented in Figure 4, and those of the tris fod chelates are shown in Figure 5. 

Windsor and his co-workers 10, 11) have shown, by direct excitation of the levels in a number of europium compounds, that the quantum yield of fluorescence decreases progressively as one successively excites Do, Di, and Do. While the yield on direct excitation of Do is quite dependent on the particular compound and medium (the value is 0.82 for the thenoyltrifluoroacetone chelate in acetone solution), the proportion of the energy lost between e.g. - Do and - Do within a given compound is rather insensitive to changes in the environment. These nonradiative processes from " D and Di, whose nature is not understood, would appear to be responsible for most of the ca. 40% energy loss in these materials. 

The most common use of europium compounds is in making phosphors. A phosphor is a material that shines when stmck by electrons. The color... 

Fluorosulphates of most of the lanthanide elements in the oxidation state iii have been prepared by the action of peroxydisulphuryl difluoride on the anhydrous metal carbonates. The oxides of neodymium, samarium, and europium, however, gave indications of partial reaction with S2O6F2 to form mixtures of fluorosulphate with oxide. The vibrational spectra and structure of the lanthanide fluorosulphates suggested the presence of mixed co-ordination type anions. Fluorescence emission, and vibrational spectra of the europium compound indicated octaco-ordination and the presence of ter- and bi-dentate fluorosulphate groups. 

Solid Europium Compounds. Solid europium oxide, chalcogenides, halides, carbonate, phosphate, etc., may be obtained by reduction of the corresponding Eu3 + compounds or, metathetically, from EuC12. The metal reacts with liquid ammonia at 50° to give the orange amide, Eu(NH2)2, which gives EuN when heated.54 The compounds are usually isostructural with the Sr2 + or Ba2+ analogs. However, definite lower fluorides and chlorides appear to exist except for La, Ce, Pr, Gd, Tb and Er.57... 

In Table 4, data on compounds are given which have been also investigated by neutron diffi action. Although the hydrogen positions were poorly determined in case of X-ray diffraction measurements, the X-O distances originating from neutron diffraction and X-ray diffraction for the same compounds are consistent in a satisfying manner. For the europium compound, EuH(Se04)2 [63], the Se-O value... 

It is difficult to measure a quadrupole splitting in europium compounds because of the electronic configurations of Eu and Eu " ". The Eu ion has a, Af half-filled shell with an electronic ground state of which cannot... 

---