Yttrium deposition

This also illustrates the use of different wavelengths of light to obtain much more infomration on the nature of the film. Here A and T are plotted versus the wavelength of light ( ) and the line drawn tln-ough these data represents a fit calculated for the various fihns of yttrium oxide deposited on silica as shown at tire bottom of the figure [40],... 

Electrical and Electronic Applications. Silver neodecanoate [62804-19-7] has been used in the preparation of a capacitor-end termination composition (110), lead and stannous neodecanoate have been used in circuit-board fabrication (111), and stannous neodecanoate has been used to form patterned semiconductive tin oxide films (112). The silver salt has also been used in the preparation of ceramic superconductors (113). Neodecanoate salts of barium, copper, yttrium, and europium have been used to prepare superconducting films and patterned thin-fHm superconductors. To prepare these materials, the metal salts are deposited on a substrate, then decomposed by heat to give the thin film (114—116) or by a focused beam (electron, ion, or laser) to give the patterned thin film (117,118). The resulting films exhibit superconductivity above Hquid nitrogen temperatures. 

The alkoxides and aryloxides, particularly of yttrium have excited recent interest. This is because of their potential use in the production of electronic and ceramic materials,in particular high temperature superconductors, by the deposition of pure oxides (metallo-organic chemical vapour deposition, MOCVD). They are moisture sensitive but mostly polymeric and involatile and so attempts have been made to inhibit polymerization and produce the required volatility by using bulky alkoxide ligands. M(OR)3, R = 2,6-di-terr-butyl-4-methylphenoxide, are indeed 3-coordinate (pyramidal) monomers but still not sufficiently volatile. More success has been achieved with fluorinated alkoxides, prepared by reacting the parent alcohols with the metal tris-(bis-trimethylsilylamides) ... 

The acetylacetonates are stable in air and readily soluble in organic solvents. From this standpoint, they have the advantage over the alkyls and other alkoxides, which, with the exception of the iron alkoxides, are not as easily soluble. They can be readily synthesized in the laboratory. Many are used extensively as catalysts and are readily available. They are also used in CVD in the deposition of metals such as iridium, scandium and rhenium and of compounds, such as the yttrium-barium-copper oxide complexes, used as superconductors. 1 1 PI Commercially available acetyl-acetonates are shown in Table 4.2. 

Also increasingly common, as CVD precursors, are many halogen-acetylacetonate complexes, such as trifluoro-acetylacetonate thorium, Th(C5H4F302)4, used in the deposition of thoriated tungsten for thermionic emitters, the trifluoro-acetylacetonates of hafnium and zirconium and the hexafluoro-acetylacetonates of calcium, copper, magnesium, palladium, strontium, and yttrium. 

Attempts to deposit yttria-stabilized zirconia by combining Reaction (1) and a similar hydrolysis of YCI3 as source of yttrium at 700-1000°C were inconclusive, Codeposition from the chlorides... 

MOCVD of Zirconia. Yttria-stabilized zirconia is also deposited by MOCVD.Deposition can be accomplished by the codecomposition of the tetramethyl heptadiones of zirconium and yttrium, Zr(CjjHj902)3 and Y(CjjHj902)3, at 735°C. Deposition is also achieved by the decomposition of the trifluoro-acetylacetonates in a helium atmosphere above 300°C.P 1 Other potential MOCVD precursors are bis(cyclopentadienyl)zirconium dichloride, (C5H5)2ZrCl2, and zirconium (IV) trifluoroacetylacetonate,... 

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 ]... 

YBa2Cu307 films are also obtained by MOCVD from a mixture of acetyl acetonates (tetramethyl heptadionate) of yttrium, barium, and copper, typically at a pressure of 5 Torr and at a deposition temperature of These precursor materials... 

The sacrificial core approach entails depositing a coating on the surface of particles by either the controlled surface precipitation of inorganic molecular precursors from solution or by direct surface reactions [2,3,5,6,8,9,33-35,38], followed by removal of the core by thermal or chemical means. Using this approach, micron-size hollow capsules of yttrium compounds [2], silica spheres [38], and monodisperse hollow silica nanoparticles [3,35] have been generated. 

This method emplosrs a molten flux which dissolves the material and re-deposits it upon a seleeted substrate. That is, the molten flux acts as a transport medium. The temperature of the flux can be varied to suit the material and to promote high solubility of the solute material in the molten solvent. One example is YIG", yttrium iron garnet, i.e.- Y3FesOi2 -This material is used in the Electronics Industry as single crystals for microwave generating devices. It can be grown via the molten flux method. 

Bastnaesite belongs to the carbonatite group of minerals that contain REOEs. Beside the cerium group of elements, bastnaesite also contains yttrium and europium. Typically, it contains 65-75% REOE. Bastnaesite is usually found in pegmatites, carbonatite and hydrothermal ore bodies in alkaline gangue minerals. Because it is poor chemically and stable, it is not found in mineral sand deposits. 

This hydroxamate is selective towards calcite, fluorite and sericite. The yttrium group minerals that contain zircon also have highly complex mineral compositions. These ores contain fergusonite, euxenite and priorit besides other minerals that contain REO. Such deposits are found in Northern Canada (Thor Lake). 

Rare earth stabilization, as it relates to zeolite performance, has already been discussed. However, catalyst performance also varies depending on how the rare earths are deposited within the zeolite and the matrix, and also on how the ratio of individual species (such as lanthanum, cerium, and the other rare earths) are distributed. Yttrium can also be used to enhance zeolite catalyst performance and stability. These also seem to help mitigate the detrimental effect of vanadium, the most common and controversial contaminant. 

Yttrium is also used in other areas of metallurgy notably as a component of certain nickel-base and cobalt-base superalloys of the NiCrAlY and CoCrAlY type.(3) These alloys possess excellent corrosion and oxidation resistance, properties that have attracted the attention of the aero-engine industry where they are used as protective coatings on turbine blades. The alloys, when applied by vapour deposition, form an oxide coating that exhibits remarkable adhesion, a property attributed largely to the yttrium component acting to prevent the formation of voids at the oxide/substrate interface.(4)... 

Film Critical Current Densities Critical current densities of thin films have been reported by several hundreds of papers a few representative but by no means inclusive are noted here in addition to those mentioned above. Desirable attributes of thin films for technology are high transition temperature to zero resistance, high critical current, low substrate temperature during deposition, no high temperature post anneal, and atomically smooth surface without pinholes. A thermal coevaporation of yttrium, barium, and copper in an oxygen atmosphere have been deposited by Berberich (34) on substrates at 650°C with Tc s of 91 K on MgO and 89 K on SrTiOs without post anneal. Although critical currents of 106 A/cm2 were obtained at 4 K, values of 104 A/cm2 were found at 77 K. However,... 

One important aspect of such coating processes is the generality of the procedure. It would appear that specific surface characteristics of the preformed particles are not necessarily essential for the successful deposition of the new layer. For example, yttrium basic carbonate coatings were produced on zirconium basic sulfate... 

Basic yttrium carbonate [Y(OH)COs] was deposited by CD and snbseqnently annealed in air at 600°C to Y2O3 [51 ]. Si wafers and self-assembled monolayers with sulphonate endgronps were used as substrates. An aqneons solntion of YNO3 and urea was heated at 80°C in sealed vials. The increase in pH, together with generation of carbonate from hydrolysis of urea (Sec. 3.2.4.1), resulted in formation of the basic carbonate. 

Yttrium-doped ZrOi was deposited by adding 2(804)3 and urea and depositing at 80°C (see deposition of Y2O3 described earlier). A higher pH (2.5-3.0)... 

Jhe distribution of beryllium, boron, titanium, vanadium, chromium, cobalt, nickel, copper, zinc, gallium, germanium, tin, molybdenum, yttrium, and lanthanum in the principal coal-producing beds of the Interior Province has been studied by the U. S. Geological Survey. Data, methods of sampling, and analyses are discussed by Zubovic and others (II, 12). This chapter discusses the occurrence of 13 of these elements with respect to geological and geochemical environments of coal deposition and chemical properties of the elements. Zinc and tin are not included in this study because they were detected in only a few samples. 

The salts of the alkali and alkaline earth metals, as well as of gold, magnesium, beryllium and yttrium, are soluble in water, the solutions being colourless or pale yellow. They gradually decompose, however, when kept, with deposition of sulphur, arsenic and arsenic pentasulphide. The following thioarsenates have been described. 

Residues from uranium mining operations in Canada have been a major source of yttrium. Xenotime (YP04) found in Malaysia is another source, as well as the ion-adsorption clay minerals in China, Some apahte deposits are unusually rich in yttrium and it also is found in gadolimte, euxenite, and samarskite. 

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