Iron garnets

Group III with electronic configuration 5s 4d . The principal ore is gadolinite (a silicate also containing lanthanides). Y2O3 containing Eu is used as a red phosphor in colour television. Yttrium iron garnets are used as microwave filters. 

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

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. 

See p. 500 of ref. 24 for a description of Ihe garnet structure which is also adopted by inany. synthetic and non-silicaie coniponnds these have been much stndied recently becan.se of their important optical and magnetic properties, e.g. ferrimagnetic vitriuni iron garnet (YIG), y> Fe (Al" b4),. 

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. 

Kalk-echtlieit. /. fastness to lime, -einlagerung, /. calcareous deposit, -eisengranat, m. lime-iron garnet, andradite. -eisenstein, m, ferruginous limestone, kalkempfindlich, a. sensitive to lime. Kalkempfindlichkeit, /. sensitiveness to lime, kalken, kalken, v.t. lime. 

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. 

YIG (yttrium iron garnet), Y3Fe5012, has the same structure as garnet. Which are the appropriate sites for the Y3+ and Fe3+ ions If the electrostatic valence rule is insufficient for you to come to a decision, take ionic radii as an additional criterion. 

In yttrium iron garnet Y3Fe5012 ( YIG ) a ferrimagnetic coupling (superexchange) is active between the octahedral and the tetrahedral sites. Since the tetrahedral sites are in excess, the magnetic moments do not compensate each other. The magnetic properties can be varied by substitution of yttrium by lanthanoids. 

Garnet, yttrium iron garnet, cI160, structural type... 

Among the best-known garnets Y3Fe2Fe3012 (Y3Fe5012 yttrium-iron garnet YIG) for its magnetic properties and applications, Y3A15012 (YAG, important laser host material). 

The most important apphcation of this metal is as control rod material for shielding in nuclear power reactors. Its thermal neutron absorption cross section is 46,000 bams. Other uses are in thermoelectric generating devices, as a thermoionic emitter, in yttrium-iron garnets in microwave filters to detect low intensity signals, as an activator in many phosphors, for deoxidation of molten titanium, and as a catalyst. Catalytic apphcations include decarboxylation of oxaloacetic acid conversion of ortho- to para-hydrogen and polymerization of ethylene. 

Yttrium alloys have many applications. The metal doped with rare earths such as europium is used as phosphor for color television receivers. When added to iron, chromium, vanadium, niobium, and other metals it enhances resistance of these metals and their alloys to high temperature oxidation and recrystallization. It is a deoxidizer for vanadium and other nonferrous metals. Yttrium-aluminum garnets are used in lasers and in jewelery gemstones. Yttrium-iron garnets are used as transmitters and as transducers of acoustic energy. 

The oxide is used in phosphors that form red color in color television tubes. Also, it is used in gas mantles and acetylene hghts. Other uses are in yttrium-iron garnets for microwave filters in lasers, and as a stabdizer for high temperature in refractories. 

Recently, spherical yttrium iron garnet (Y1G) particles over a broad range of sizes were obtained by hydrolysis at 90°C of acidic urea solutions containing the respective metal salts (33). 

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