Garnets yttrium iron garnet

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

The absorption due to relaxation between the possible directions of the Jahn-Teller distortions was observed initially in experiments done on the crystals of aluminum oxide (corundum), yttrium aluminum garnet, yttrium iron garnet, and lithium gallium spinel doped with 2>d ions [10,11]. 

Now we will overview some experiments that reveal the specificities of the Jahn-Teller effect in diluted crystals. First of all, we will discuss a justification of their relaxation origin. We have mentioned before that the first experiments were done on the crystals of aluminum oxide (corundum), yttrium aluminum garnet, yttrium iron garnet, and lithium gallium spinel doped with a number of 3d ions [10,11]. The main result was the discovery of attenuation maximum which was considered to be observed at cot 1 and reconstruction of the relaxation time temperature dependence. In some experiments reported later both the velocity and attenuation of ultrasound were measured as functions of the temperature. They were done on ZnSe and ZnTe crystals doped with transition metals. These crystals have the zinc-blende structure with the Jahn-Teller ion in tetrahedral coordination. The following... 

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. 

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. 

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. 

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. 

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). 

Magnetic properties are important in the function of electronic devices. An example is the use of yttrium iron garnet (YIG) in microwave devices. On applying an external magnetic field to a YIG disk, the input, say energy of one particular frequency selectively passes to the output. Thin films based of YIG within which magnetic waves can pass have proven to be useful. The use of lanthanides in magnetic devices as transducers is listed in Table 12.18. 

Small amounts of Y or La are used to dope BaTiC>3 which is the main component of all PTCs (positive temperature coefficient). Demand for PTC thermistors is high. Yttrium iron garnets are used in soft ferrites at very high frequencies (microwave region) for radar equipment. 

Yttrium iron garnet (YIG) is used in devices that process microwaves. Growing YIG and LnIG films on perfect crystals obtained from gadolinium gallium garnet (GGG) is involved in ceramics which have technological applications. 

Yttrium compounds are frequently useful host materials for later Ln + ions, as mentioned in Section 5.4.4 Eu Y2O2S is the standard material for the red phosphor in virtually all colour and television cathode ray tubes, whilst Eu Y203 is used for energy-efficient fluorescent tubes. Yttrium oxide is used to stabilize zirconia (YSZ), yttrium iron garnets (YIG) are used in microwave devices, and of course YBa2Cu307 is the classic warm superconductor. Yttrium, like scandium, is naturally monoisotopic. Y has I = 1/2 though signals can be difficult to observe, valuable information can be obtained from NMR studies. 

Monophosphate tungsten bronzes with pentagonal tunnels NASICON = Sodium super ionic conductor NLO = Nonlinear Optical PLZT = Lead lanthanum zirconium titanate PZT = Lead zirconium titanate SBT = Strontium Bismuth Tantalate, SrBi2Ta209 SOFC = Solid oxide fuel cell TTB = Tetragonal tungsten bronze YAG = Yttrium iron garnet 3D = Three-dimensional TEOS = Tetraethylorthosilicate. 

In ionic crystals it seems reasonable that the background level should fall to zero at suitably chosen positions in the unit cell so that a moment integration may 3neld the local moment directly. Such a procedure was followed for integration around the octahedral and tetrahedral Fe3+ sites in yttrium iron garnet (72), where the position of the yttrium ion was chosen as the backgound level. This technique is particularly useful in such cases where there is more than one type of magnetic ion per unit cell. 

NiO (56) (Section 4.1). The only way to avoid such a calibration apart from extrapolation using a particular shape for f(>e) is to estimate the total spin by integration of the moment density determined by Fourier transformation of single crystal data, which carries its own problems (Section 3.7) as well as being a vastly more time-consuming experiment. This procedure has been carried out (73) however for octahedral and tetrahedral Fe + in yttrium iron garnet (YIG). 

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