YBCO superconductor

Bhattacharya, R. N. Phok, S. Spagnol, P Chaudhuri, T. 2006. Electrodeposited biaxially textured buffer layer for YBa2Cu307 5 (YBCO) superconductor oxide films. J. Electrochem. Soc. 153 C273-C276. 

When multicomponent alkoxide solutions, or a single alkoxide and a soluble inorganic salt, are mixed, a multicomponent alkoxide may result. In this way, such complex oxides such as the YBCO superconductor (cf. Section 6.1.2.4) can be formed. Sol-gel processing can also be used to coat fibers for composites and to form ceramics with very fine pore sizes called xerogels. A xerogel commonly contains 50-70% porosity, a pore size of 1-50 nm, and a specific surface area exceeding 100 m /g. 

Fig. 6.27. Structure of the YBCO superconductor (adapted from Ceder (1994)).

Murakami, M., Flux pinning of melt textured processed YBCO superconductors and their applications, in Studies of High Temperature Superconductors, Vol. 9 (A. V. Narlikar, ed.). Nova Science, New York, 1991, pp. 1. 

The transition temperature (Tc) for the YBCO superconductor is 95 K. Higher T s are found with other ceramic high-temperature superconductors, but these materials are not being used commercially. What are some of the other materials and what are some of the factors that are limiting their use ... 

The manganates have the layered perovskite structure similar to that found in the YBCO superconductor (see Section 7.16). This similarity is particularly interesting and may lead to increased understanding of both types of material. The nature of the interactions in the manganites is complicated. They show a metal-insulator transition and a ferromagnetic-antiferromagnetic transition associated with CMR. 

To date, many of the ceramic superconductors contain copper and share a common structural feature copper and oxygen atoms bonded together in planar sheets. In YBCO superconductors, the Cu—O planes are widely separated. In bismuth superconductors, the Cu—O planes occur in "sandwiches" consisting of two closely spaced sheets separated by a layer of group 2 ions. These sandwiches are separated from one another by several layers of bismuth oxide. In the thallium superconductors, the Cu—O planes are stacked in groups of three, like triple-decker sandwiches. 

TABLE 1 Composition of Two Microemulsions for Synthesizing Nanoparticles of YBCO Superconductors... 

Faiz et al. (1996) have applied micro-PIXE analysis to study solute distributions in a single crystal sample of YiBa2Cu307 5 high temperature superconductor (YBCO) of dimensions 1.3 mm x 1.5 mm x 75 pm. It contained a small secondary crystal overgrowth of dimensions 340 x 340 x 100 pm3. The interface region between the smaller crystal and the base crystal was covered with a material which appeared to be residual flux. The instrument employed a 2.5 MeV focused proton beam of about 4 pm resolution, which could scan an area of 500 x 500 pm2 on the sample surface. The microbeam current was kept low (typically about 30 pA) to avoid any damage to the sample. 

The temperature of decomposition of carbonates of the YBCO high-temperature superconductor to oxides [97] ... 

Non-stoichiometric compounds are of potential use to industry because their electronic, optical, magnetic, and mechanical properties can be modified by changing the proportions of the atomic constituents. This is widely exploited and researched by the electronics and other industries. Currently, the best known example of non-stoichiometry is probably that of oxygen vacancies in the high temperature superconductors such as YBCO (1-2-3) (YBa2Cu307 J. The structure of these is discussed in detail in Chapter 10. 

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... 

This discovery stimulated what can only be described as frenzied research in many laboratories throughout the world which quickly resulted in the discovery of YBa2Cu307, the so-called T23 phase, or YBCO, with a transition at a temperature as high as 93 K. There are also bismuth-based high-Tc superconductors, which are described below. 

Figure 2.20. Comparison of the crystal structures of Ocft-right) LSCO, YBCO, and BSCCO superconductors, respectively. Reproduced with permission from Prof. Hoffman s webpage at Harvard University http //hoffman.physics.harvard.edu/research/SCmaterials.php...

A recent preprint [38] dealing with the chain buckling distortion in the high temperature superconductor, YBCO, is an example of such an analysis and which urgently calls for a new approach to the problem. Our method should be a viable alternate in the near future in addressing such problems. For this we need to provide the functional of two variables, the electron density and the ion coordinate. 

The discovery of high-77 superconductors in the late 1980s led to the need to produce homogeneous and high-purity complex metal oxide species, a need that could be met by the use of sol-gel techniques. The first sol-gel routes to yttrium barium copper oxide (YBCO) involved coprecipitation,222 but latterly, routes based on the hydrolysis and condensation of yttrium and barium alkoxides with copper methoxyethoxide have been developed. It is found that the hydrolysis ratio used in the production of the gel can affect the temperature of the onset of Tc and the sharpness of the transition to superconductivity.223... 

---