Y2O3

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. 

Figure Bl.26.17. (a) Observed and calculated ellipsometric [A(1), T(>l)] spectra for the Y2O3 film on vitreous silica. Angle of incidence 75°. (b) Best-fit model of the Y2O3 film on vitreous silica (Chindaudom P and Vedam K 1994 Physics of Thin Films vol 19, ed K Vedam (New York Academic) p 191).

Yttrium oxide is one of the most important compounds of yttrium and accounts for the largest use. It is widely used in making YVOr europium, and Y2O3 europium phosphors to give the red color in color television tubes. Many hundreds of thousands of pounds are now used in this application. 

The thermal barrier eoatings have an insulation layer of 100-300 pm thiek, and are based on Zr02—Y2O3 and ean reduee metal temperatures by 90-270 °F (50-150 °C). This type of eoating is used in eombustion eans, transition pieees, nozzle guide vanes, and also blade platforms. 

S. Bebelis, and C.G. Vayenas, Non-Faradaic Electrochemical Modification of Catalytic Activity 6. The epoxidation of Ethylene on Ag/Zr02(8mol%) Y2O3, J. Catal. 138, 588-610(1992). 

P. Tsiakaras, and C.G. Vayenas, Oxidative Coupling of CH4 on Ag catalyst-electrodes deposited on Zr02(8mol% Y2O3), J. Catal. 144, 333-347 (1993). 

To avoid this phase change, zirconia is stabilized in the cubic phase by the addition of a small amount of a divalent or trivalent oxide of cubic symmetry, such as MgO, CaO, or Y2O3. The additive oxide cation enters the crystal lattice and increases the ionic character of the metal-oxygen bonds. The cubic phase is not thermodynamically stable below approximately 1400°C for MgO additions, 1140°C for CaO additions, and below 750°C for Y2O3 additions. However, the diffusion rates for the cations are so low at Xhtstsubsolidus temperatures that the cubic phase can easily be quenched and retained as a metastable phase. Zirconia is commercially applied by thermal spray. It is also readily produced by CVD, mostly on an experimental basis. Its characteristics and properties are summarized in Table 11.8. 

Two types of reactors were used One was a CSTR type consisting of an Y2O3 (8mol%)-stabilized Z1O2 (YSZ) tube (length 15 cm, diameter 2 cm) closed flat at one end with an appropriately machined water-cooled stainless steel reactor cap attached to the other end, thus allowing for continuous gas feed and... 

MIECs may be made nonuniform to the extent that they become n-type on one side and p-type on the other side, thus forming pn or pin (/ = intrinsic) junctions. Zr02 + 10 mol % Y2O3 subject to an oxygen partial pressure, Pq, gradient at elevated temperatures becomes p-type near the high (P —l atm) side and n-type near the low P,... 

As it has been mention in preceding section, the vast effect of the mechanism of adsorption-caused change in electrophysical characteristics of adsorbent is provided by availability of defects [32]. However, various admixtures play similarly important role on effects of properties of oxides including the sensitivity of their electrophysical properties to adsorption [4, 5]. Small amounts of admixtures (of the order of 0.5 -1 mol.-%) can both increase the sensitivity of oxide for instance to oxygen (addition of Y2O3 to calcium oxide over pressure interval lO -10 Torr [189]) and decrease it (addition of Ga203 to ZnO [190]), or can result in insensitivity of electric conductivity on the pressure of the gas in question (as it is the case with respect to O2 while adding 0.5 -1 mol.-% of lithium to NiO [190]). 

---