Halides yttrium

The diatomic yttrium halides have been the topic of both ab initio and experimental studies. Fischell et al. (1980) have studied the excitation spectra of the YCl diatomic molecule using the laser-induced fluorescence (LIF) method. More recently, Xin et al. (1991) have studied the B ri-X system of YCl in high resolution. The rotational analysis of the observed bands has yielded very accurate molecular constants for the X and B states of YCl. Shirley et al. (1990) have studied the molecular-beam optical Stark spectrum of the B n(t = 0)-X (t = 0) band system of YF. The permanent dipole moment and the magnetic hyperfine parameter a for the B n state have been determined as 2.96(4) D and 146.8(3) MHz, respectively. The dipole moment of the X S state was determined as 1.82(8)D. More recently, Shirley et al. (1991) have employed the molecular-beam millimeter-wave optical pump-probe spectroscopy to study pure rotational transitions of the YF ground state. This study has yielded improved ground-state rotational constants as B = 8683.65(1) MHz and D = 0.0079(2)-MHz, respectively. 

Langhoff et al. (1988) have computed the spectroscopic constants of scandium and yttrium halides using ab initio method. In particular, the YCl diatomic molecule has been studied using CASSCF followed by MRCI and MRCI + Q methods. These authors have computed the spectroscopic constants of 18 electronic states of YCl and reassigned the observed spectra of Fischell et al. (1980). We discuss this in this section. 

Block, F.E. and T.T. Campbell, 1961, Rare Earth and Yttrium Halides for Metal Production-Chlorides Bromides Iodides, in Spedding, F.H. and A.H. Daane, eds.. The Rare Earths (John Wiley and Sons, New York), pp. 89-101. 

Table 30.5 Stoichiometries and structures of reduced halides (X/M < 2) of scandium, yttrium, lanthanum and the lanthanides...

Other detrimental factors which should to be taken into account in the materials selection process include temperature cycling and the presence of halide gases. Specialist alloys containing rare earth element additions such as cerium, lanthanum and yttrium have been developed for use in certain environments up to 130°C. 

The deposition of thin films of the high-temperature superconductor yttrium-barium-copper oxide, YBa2Cu307, is obtained from the mixed halides, typically YCI3, Bal2, and CUCI2, with O2 and H2O as oxygen sources. Deposition temperatures are 870-910°C.f ]... 

The values of AH for the thallium (III) halide systems becomes less exothermic as complex formation proceeds. There are no steps with about the same value of AH , in marked contrast to e.g. Hg2+ and Pd2+. The trend of AH is in fact opposite to that found for several t)q)ical hard-hard interactions, e.g. iron (III) fluoride, lanthanum sulphate and yttrium acetate (Table 1). An even more striking feature of the thallium (III) halides is that AS°n is approximately constant for all steps. This is indeed different not only from ions such as In +, Cd2+ and Zn +, where reversals of the decreasing trend of AS°n occur for certain steps, but also from Hg2+ and Pd + where the higher steps have a much lower value of ASn than the earlier ones. 

Calcium metal is an excellent reducing agent for production of the less common metals because of the large free energy of formation of its oxides and halides. The following metals have been prepared by the reduction of their oxides or fluorides with calcium hafnium (22), plutonium (23), scandium (24), thorium (25), tungsten (26), uranium (27,28), vanadium (29), yttrium (30), zirconium (22,31), and most of the rare-earth metals (32). 

Many highly reduced halides of scandium, yttrium, and zirconium have been found to have infinite metal-metal bonded chains.169 Zirconium chloride, for example, contains double metal layers alternating with double chlorine layers (Fig. 16.68). It was dis-... 

The isostructural solutions formed by yttrium(III) and erbium(III) have been used to study the structures of their halide complexes in aqueous solutions at different concentrations (35). The RDFs for some erbium(III) bromide and chloride solutions with different metal ion concentration and halide to metal ratios are given in Fig. 20 after elimination of the nonmetal interactions. For comparison those of three perchlorate solutions of similar concentrations are also given. For all of these solutions the peaks at 2.35 A, which correspond to the inner coordination sphere of the metal ion, are nearly the same and are closely reproduced by a theoretical peak calculated for 8.0 Er-H20 interactions. This indicates that the anions do not penetrate the first... 

No carbonyl chemistry of scandium and yttrium has been reported yet and there is also no cyanide chemistry of these two elements although thiocyanato complexes of scandium [Sc(NCS)6]3 (bonded through nitrogen) are known. The important developments involving scandium or yttrium with carbon have involved the fullerene derivatives of these elements. There have been some scandium carbide systems prepared but these will be highlighted in the chemistry of the halides. 

Complex halides of scandium and yttrium have been discussed in CCC (1987).1 Most halides and halide complexes reported are of Sc111 and Y111 but there are some reduced halide species such as the diiodide.229... 

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