Garnets 348 oxide

K. J. Standley, "Electrical Properties of Ferrites and Garnets," Oxide Magnetic Materials, 2nd ed.. Clarendon Press, Oxford, UK, 1972. 

Magnetic garnet films are deposited on GGG substrates from solutions of the garnet oxides dissolved in PbO-B203 melts. 

Relationship between the temperature and ionic conductivity for the garnet oxide Li-Ta-Ti-O. (Adapted from Fergus, J.W., /. Power Sources 195 4554-4569,2010.)... 

Yttrium oxide also is used to produce yttrium-iron-garnets, which are very effective microwave filters. 

Chemical Vapor Deposition. In chemical vapor deposition (CVD), often referred to as vapor transport, the desired constituent(s) to be deposited are ia the form of a compound existing as a vapor at an appropriate temperature. This vapor decomposes with or without a reducing or oxidizing agent at the substrate— vapor interface for film growth. CVD has been used successfully for preparing garnet and ortho ferrite films (24,25). Laser-assisted CVD is also practiced. 

Coated abrasives, such as sheets, disks, and dmms, are used for polishing and finishing. Here, too, the abrasives, such as aluminum oxide and siHcon carbide, have replaced the flint and garnet of common sandpaper. These industrial coated abrasives are manufactured from cloth or tough paper base. 

Titanium Silicates. A number of titanium siUcate minerals are known (160) examples are Hsted in Table 19. In most cases, it is convenient to classify these on the basis of the connectivity of the SiO building blocks, eg, isolated tetrahedra, chains, and rings, that are typical of siUcates in general. In some cases, the SiO units may be replaced, even if only to a limited extent by TiO. For example, up to 6% of the SiO in the garnet schorlomite can be replaced by TiO. In general, replacement of SiO by TiO bull ding blocks increases the refractive indices of these minerals. Ti has also replaced Si in the framework of various zeofltes. In addition, the catalytic activity of both titanium-substituted ZSM-5 (TS-1) and ZSM-11 (TS-2) has received attention (161), eg, the selective oxidation of phenol, with hydrogen peroxide, to hydroquinone and catechol over TS-1 has been operated at the 10,000 t/yr scale in Italy (162). 

Garnets have played an important role in the development of highly sophisticated microwave devices since the development of yttrium—iron garnet, yttrium iron oxide [12063-56-8]. The iron is strongly constrained to be trivalent in order to maintain electrical neutraUty in the crystal, which is essential for low microwave losses. Garnets have lower values of saturation magneti2ation than spinels, but provide superior performance in microwave devices because they have a narrower resonance line width. 

A U.S. Bureau of Mines survey covering 202 froth flotation plants in the United States showed that 198 million tons of material were treated by flotation in 1960 to recover 20 million tons of concentrates which contained approximately 1 billion in recoverable products. Most of the worlds copper, lead, zinc, molybdenum, and nickel are produced from ores that are concentrated first by flotation. In addition, flotation is commonly used for the recoveiy of fine coal and for the concentration of a wide range of mineral commodities including fluorspar, barite, glass sand, iron oxide, pyrite, manganese ore, clay, feldspar, mica, sponumene, bastnaesite, calcite, garnet, kyanite, and talc. 

In the ceramics field many of the new advanced ceramic oxides have a specially prepared mixture of cations which determines the crystal structure, through the relative sizes of the cations and oxygen ions, and the physical properties through the choice of cations and tlreh oxidation states. These include, for example, solid electrolytes and electrodes for sensors and fuel cells, fenites and garnets for magnetic systems, zirconates and titanates for piezoelectric materials, as well as ceramic superconductors and a number of other substances... 

So-called hexagonal ferrites such as BaFe -Oi9 are ferrimagnetic and are used to construct permanent magnets. A third type of ferrimagnetic mixed oxides are the garnets, Mj FejOjj, of which the best known is yttrium iron garnet (YIG) used as a microwave filter in radar. 

Nearly no eddy current losses occur in electrically insulating magnetic materials. This is one of the reasons for the importance of oxidic materials, especially of spinels and garnets. Another reason is the large variability of the magnetic properties that can be achieved with spinels and garnets of different compositions. The tolerance of the spinel structure to substitution at the metal atom sites and the interplay between normal and inverse spinels allow the adaptation of the properties to given requirements. 

Figure 15.1 Comparison of the hot hardnesses of three strong oxides and the strong intermetallic compound, Ni3Al. Yttrium aluminum garnet is the hardest of all oxides at high temperatures.

Fig. 7 Creep-resistance of the eutectic fiber consisting of interpenetrating phases of alpha-alumina and yttrium-aluminum-garnet (YAG) up to very high temperatures compared with other types of oxide fibers... 

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