Yttrium oxo salts

Pure hafnium dioxide transforms into the tetragonal stmcture at about 1700°C. The difference between the heating transformation temperature and the cooling transformation temperature is 40—80°C, considerably less than for zirconia. The hafnium dioxide undergoes a shrinkage of about 3% upon transforming into the tetragonal phase. The tetragonal form converts to a cubic polymorph having the fluorite stmcture above 2600°C. The fluorite stmcture can be rendered stable at lower temperatures by addition of erbium oxide, yttrium oxide, calcium oxide, or magnesium oxide. Compared to zirconium oxide, the higher transformation temperature of hafnium oxide, pure or stabilized, has aroused considerable interest (64) and should lead to several specialized appHcations. Reference 64 is a thorough review of hafnium oxide and hafnium oxide-toughened ceramics.  [c.445]

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.  [c.106]

The term solid-state laser refers to lasers that use solids as their active medium. However, two kinds of materials are required a host crystal and an impurity dopant. The dopant is selected for its ability to form a population inversion. The Nd YAG laser, for example, uses a small number of neodymium ions as a dopant in the solid YAG (yttrium-aluminum-gar-net) crystal. Solid-state lasers are pumped with an outside source such as a flash lamp, arc lamp, or another laser. This energy is then absorbed by the dopant, raising the atoms to an excited state. Solid-state lasers are sought after because the active medium is relatively easy to handle and store. Also, because the wavelength they produce is within the transmission range of glass, they can be used with fiber optics.  [c.705]

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.  [c.900]

For organometailic compounds, the situation becomes even more complicated because the presence of elements such as platinum, iron, and copper introduces more complex isotopic patterns. In a very general sense, for inorganic chemistry, as atomic number increases, the number of isotopes occurring naturally for any one element can increase considerably. An element of small atomic number, lithium, has only two natural isotopes, but tin has ten, xenon has nine, and mercury has seven isotopes. This general phenomenon should be approached with caution because, for example, yttrium of atomic mass 89 is monoisotopic, and iridium has just two natural isotopes at masses 191 and 193. Nevertheless, the occurrence and variation in patterns of multi-isotopic elements often make their mass spectrometric identification easy, as depicted for the cases of dimethylmercury and dimethylplatinum in Figure 47.4.  [c.349]

Laser action can be induced in Nd ions embedded in a suitable solid matrix. Several matrices, including some special glasses, are suitable but one of the most frequently used is yttrium aluminium garnet (Y3AI5O12), which is referred to as YAG.  [c.349]

In order to make an efficient Y202 Eu ", it is necessary to start with weU-purifted yttrium and europium oxides or a weU-purifted coprecipitated oxide. Very small amounts of impurity ions, particularly other rare-earth ions, decrease the efficiency of this phosphor. Ce " is one of the most troublesome ions because it competes for the uv absorption and should be present at no more than about one part per million. Once purified, if not already coprecipitated, the oxides are dissolved in hydrochloric or nitric acid and then precipitated with oxaflc acid. This precipitate is then calcined, and fired at around 800°C to decompose the oxalate and form the oxide. EinaHy the oxide is fired usually in air at temperatures of 1500—1550°C in order to produce a good crystal stmcture and an efficient phosphor. This phosphor does not need to be further processed but may be milled for particle size control and/or screened to remove agglomerates which later show up as dark specks in the coating.  [c.290]

Ima.g esetters. AH modem imagesetters use a laser light source to expose the media. Imagesetters should not be confused with color film recorders, which use similar technology to expose fuU-color images onto a single piece of film. Many different laser technologies are in use, each requiring different media sensitivities (see Lasers). Helium neon, HeNe, lasers produce a visible red light (633 nm) and use media that must be handled under green safelight conditions. Argon ion, Ar", lasers produce blue light (488 nm) and aHow more convenient amber safelights to be used. Other laser sources include far red laser diodes (785 nm), frequency-doubled yttrium aluminum garnet (YAG) lasers (532 nm), and infrared laser diodes (826 nm). The light produced by these lasers is focused to a tiny spot and modulated to control the placement of marks on the medium. In general, laser diodes can be modulated directly by controlling current flow to the diode, whereas gas lasers, eg, argon ion, require external beam modulation through an acousto-optic modulator (AOM) or similar device (see Light generation).  [c.37]

Another application is in tire oxidation of vapour mixtures in a chemical vapour transport reaction, the attempt being to coat materials with a tlrin layer of solid electrolyte. For example, a gas phase mixture consisting of the iodides of zirconium and yttrium is oxidized to form a thin layer of ytnia-stabilized zirconia on the surface of an electrode such as one of the lanthanum-snontium doped transition metal perovskites Lai j.Srj.M03 7, which can transmit oxygen as ions and electrons from an isolated volume of oxygen gas.  [c.242]

Solid oxide fuel cells consist of solid electrolytes held between metallic or oxide elecU odes. The most successful fuel cell utilizing an oxide electrolyte to date employs Zr02 containing a few mole per cent of yttrium oxide, which operates in tire temperature range 1100-1300 K. Other electrolytes based  [c.244]

Me3Si)2NH, Me3SiCl, Pyr, 20°, 5 min, 100% yield. ROH is a carbohydrate. Hexamethyldisilazane (HMDS) is one of the most common silylat-ing agents and readily silylates alcohols, acids, amines, thiols, phenols, hydroxamic acids, amides, thioamides, sulfonamides, phosphoric amides, phosphites, hydrazines, and enolizable ketones. It works best in the presence of a catalyst such as X-NH-Y, where at least one of the groups X or Y is electron withdrawing." Yttrium-based Lewis acids also serve as catalysts.  [c.117]

See pages that mention the term Yttrium oxo salts : [c.56]    [c.16]    [c.198]    [c.328]    [c.521]   
Chemistry of the elements (1998) -- [ c.949 ]