Yttrium oxide , crystal structure

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. 

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". 

Yttrium-barium-copper oxide compounds YBa2Cu306+x (x = 0.6-1), generally abbreviated to 123, with a Tc of 90K which is above the temperature of liquid nitrogen, are of great importance (2). As noted earlier, Tc is governed principally by the crystal structure... 

A breakthrough in superconductor technology came with the discovery24 of yttrium barium copper oxide, YBa2Cu307, whose crystal structure is shown here. When heated, the material readily loses oxygen atoms from the Cu-O chains, and any composition between YBa2Cu307 and YBa2Cu3Ob is observable. 

The tetraphenylporphyrin scandium complexes were previously reported and now crystal structures have been determined for the p-toly derivatives (ttp). Both scandium and yttrium form (ttp)MCl complexes150,151 but whereas the scandium compound is five-coordinate the yttrium compound coordinates solvent molecules forming seven or eight-coordinate complexes. Reaction of (ttp)ScCl with water forms an oxide dimer [Sc(ttp)]20,151 whereas for yttrium the cation [Y(ttp)(H20)3]+ has been observed.152 The structure of [Sc(ttp)]20 is shown in Figure 7, the bridging oxygen is disordered over two sites with 50% occupancy of each site. The reaction of... 

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... 

YSZ exhibits purely oxygen ionic conduction (with no electronic conduction). The crystalline array of Zr02 has two oxide ions to every zirconium ion. But in Y2O3 there are only 1.5 oxide ions to every yttrium ion. The result is vacancies in the crystal structure where oxide ions are missing. So, oxide ions from the cathode leap from hole to hole until they reach the anode [1]. 

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

Yttrium aluminum garnet (Y3AI5O12 or YAG) has a cubic crystal structure with a large cell parameter and a melting point close to that of corundum (Table I). Compression creep tests performed on YAG single crystals show that (1) it is the most creep resistant oxide presently known, and (2) its creep resistance is not strongly dependent on the crystal orientation (contrary to what is observed for corundum) [103-104]. 

Type 11 superconductors are normally limited by the Ginzburg-Landau ratio k = X/ > l/ /l. One special attribute of a high-temperature superconductor (HTS) materials is its small coherence length in comparison with a low-temperature superconductor (LTS), and its anisotropy due to the two-dimensional (2-D) character of the layered crystal structures. The coherence length is on the order of unit cell dimensions, where For example, yttrium barium copper oxide (YBCO)... 

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. 

Manthiram, A., Swiimea, J.S., Sui, Z.T., Steinfink, H., and Goodenough, JJl. (1987) The influence of oxygen variation on the crystal structure and phase composition of the superconductor yttrium barium copper oxide (YBa2Cu307 J. /. Am. 

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