Yttrium oxide structures

Goldschmidt has classed also with the ionic crystals the C-modification of the sesqui-oxides, cubic crystals with 16 M2O3 in the unit of structure. The inter-atomic distances reported by him are 2.16-2.20 A. for scandium oxide and 2.34-2.38 A. for yttrium oxide, in good agreement with the radius sums 2.21 A. for Sc+3-0= and 2.33 A. for Y+3-0". 

A common feature of all the new ceramic superconductors is that they are cuprates, that is, they are complex copper oxides. The structure of YBCO is given in Fig. 19.3, which also shows that it is related to the perovskite structure (Fig. 4.17). Synthesis of YBCO is remarkably easy appropriate amounts of dry yttrium oxide (Y203), copper oxide (CuO), and barium carbonate (BaC03) are ground together into a fine, well-mixed... 

Cubic zirconia (Zr02), with a Mohs hardness of 8, is a beautiful, usually colorless, stone that is made synthetically. Although not as hard as diamond, cubic zirconia has much fire and brilliance, and it is popular as an imitation diamond. Zirconia normally has a monoclinic crystalline structure at room temperature, but when heated to about 2,300°C (4,172°F), it takes on a cubic structure. Ordinarily, it would revert to the monoclinic structure on cooling, but the addition of yttrium oxide (Y203) or calcium oxide (CaO)... 

Some Rare Earth Oxide-Fluorides and Other Compounds with Fluorite-Derived Structures Related to Both the Baddeleyite and Yttrium Trifluoride Structure Types... 

Evans, W.J. and Sollberger, M.S. (1988) Synthetic and structural studies on the formation of a tetradecametallic yttrium oxide alkoxide chloride complex an example of how molecular yttrirrm oxygen frameworks form extended arrays. Inorganic Chemistry, 27, 4417 423. 

Al-Yassir, N. and Le Van Mao, R., Thermal stabihty of alumina aerogel doped with yttrium oxide, used as a catalyst support for the thermocatalytic cracking (TCC) process An investigation of its textural and structural properties, Appl. Catal. A, 317, 275, 2007. 

The structure of non-centrosymmetric hexagonal YIn03 at atmospheric pressure has been found to be of the LnMn03 type. The indium(iii) ions were located in five-co-ordinate trigonal-bipyramidal sites, and the yttrium(m) ions were seven-coordinate. YIn03 was reported to transform at temperatures above 1000 °C into a cubic solid solution with the c-type rare earth oxide structure. 

From the results of Table 2, it appears, depending on the amount of yttrium oxide present in zirconium oxide, that the crystal structure of the support changes from monoclinic (pure ZrOg = ZYg) to pure cubic ZY g. The presence of half of a monolayer of VgOg appears, for the first two samples, to help the... 

Yttrium oxide crystallizes in the Bixbyite (C) structure, with two inequivalent types of yttrium sites in the unit cell these sites have C2 and Csi symmetry. As electric-dipole transitions are forbidden in Csi sites (with an inversion symmetry), data on the energy levels and other optical properties of these sites are sparse and do not cover a wide range in energy. For this reason, our tabulation of data concentrates on the C2 sites. In particular, all the crystal-field parameters and energy levels given here are those appropriate for C2 sites. The C3i sites (and their interaction with C2 sites) have been studied primarily by means of far-infrared spectroscopy (Bloor and Dean, 1972), electron paramagnetic resonance (Schafer, 1969), energy-transfer studies (Heber et al., 1970), and similar methods. 

Crystal Structure and Properties of Single Crystal Yttrium Oxide... 

Joliet F, Noguera C, Thromat N et al (1990) Electronic structure of yttrium oxide. Phys Rev B 42 7587-7595... 

ZrO has a monocHnic crystal structure (M) at room temperature but is tetragonal (T) at sintering temperature. The transformation temperature is about 1200°C. If zirconium oxide is mixed with stabiHzers such as yttrium oxide Y Oj (about 6%) before sintering, the tetragonal structure remains (metastable) to room temperature. 

Yada, M., Ohya, M., Machida, M., and Kijima, T. (2000) Mesoporous gallium oxide structurally stabilized by yttrium oxide. Langmuir, 16 (10), 4752-4755. 

In many applications rare earths are used as additives. As mentioned in sect. 2, yttrium oxide is doped into zirconia to stabilize the appropriate structure for ionic conduction. 

Figure 2.6 (a) TEM image of a lamellar yttrium oxide-benzoate nanohybrid. (Reproduced from Ref. [128].) (b) HRTEM image of tungsten oxide hybrid nanostructures synthesized with deferoxamine mesylate as a structure-directing ligand. (Reproduced from... 

Meso-Macroporous Yttrium Oxides The self-formation phenomenon was also used for the preparation of hierarchically porous yttriiun oxides by a controlled polymerization of yttrium butoxide in aqueous media [12,141,144], The synthesized yttrium oxides are 0.5-2 pm in size and are covered by a smooth surface. The fissure particles with funnel-hke and parallel macrochannels below the smooth surfeice were observed by higher resolution SEM observations (Figure 32.13b). The yield of the synthesis as well as the amount of macropores per particle continuously decreases with increasing initial synthesis pH values. The macropore diameters are 1-5, 2-8, and 5-10 pm for syntheses carried out in acidic, neutral, and basic media, respectively. The macropore walls are formed by a regation of mes-ostructured nanoparticles giving a supplementary interparticle porosity centered at 30 nm. A third level of porosity is demonstrated by the inhomogeneous pores centered at 3-7 nm for syntheses in acidic and neutral media and 5-15 nm in an alkaline medium. As for all the previously described compositions, the meso-macroporous yttria structures are amorphous at the atomic scale. 

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