Barium Yttrium Copper Oxide Crystals

The high-temperature superconductors are a remarkable set of materials that present us with fascinating scientific and technological challenges. The cuprate Ba2YCu307, the first material with a T 77 K, has a tripled perovskite structure with Cu occupying the small perovskite B site while Ba and Y are ordered on the perovskite A site. Bulk crystals are key to 

The oxygen content of Ba2YCu0307, is a function of the temperature and oxygen partial pressure during annealing as shown in Fig. 3. Inside the crystal, oxygen moves by a solid-state diffusion process. The diffusion constant is temperature-dependent but is relatively slow, D = 

3 X 10 cm /s at 400°, and diffusion is mainly in the a-b plane. Thus, long anneals are required to obtain homogeneous, fully oxygenated crystals. For millimeter-sized crystals, as-grown crystals should be annealed at 400-450° for 4 weeks. Crystals can be sealed under oxygen in a clean, degassed 

All members of the lanthanoid series Ba2RECu307 with the exceptions of Ce, Tb, and Sc form tripled perovskites that are isomorphous with Ba2YCu307. Crystals of these phases can also be grown from BaCu02/Cu0-based melts. 

Crystals of BajYCU3O7 are shiny metallic gray and grow with a thin platelet shape. Fully oxygenated crystals are orthorhombic, space group Pmmm, with lattice constants a = 3.8265(4) k, b = 3.8833(2) A, and c = 11.6813(10) A at 293 K. The X-ray powder patterns is given in Table I. 

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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. 

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)... 

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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