Yttrium barium copper oxide Totally Explained

Everything about Yttrium Barium Copper Oxide totally explained

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Yttrium barium copper oxide, often abbreviated YBCO, is a chemical compound with the formula Y Ba₂Cu₃O₇. This material, a famous "high-temperature superconductor", achieved prominence because it was the first material to achieve superconductivity above the boiling point of nitrogen.

History

Seventy-five years after the discovery of superconductivity, Georg Bednorz and Alexander Müller, working at IBM in Zurich Switzerland, discovered that certain semiconducting oxides became superconducting at the then relatively high temperature of 35 K. In particular, the lanthanum barium copper oxides, an oxygen deficient perovskite-related material proved particularly promising.
Building on the motif discovered by Bednorz and Müller, Maw-Kuen Wu and his graduate students, Ashburn and Torng at the University of Alabama in Huntsville in 1987 and Paul Chu and his students at the University of Houston in 1987 (see superconductor page for info), discovered YBCO. Their work led to a rapid succession of new high temperature superconducting materials, ushering in a new era in material science and chemistry.
YBCO was the first material to become superconducting above 77 K, the boiling point of nitrogen. All materials developed before YBCO became superconducting only at temperatures near the boiling points of liquid helium or liquid hydrogen (T_b = 20.28 K). The significance of the discovery of YBCO is the breakthrough in the refrigerant used to cool the material to below the critical temperature.

Synthesis

YBCO was first synthesized by heating a mixture of the metal carbonates at temperatures between 1000 to 1300 K. ť 4BaCO₃ + Y₂(CO₃)₃ + 6 CuCO₃ → 2 YBa₂Cu₃O_{). This modest coherence length means that the superconducting state is more susceptible to local disruptions from interfaces or defects on the order of a single unit cell, such as the boundary between twinned crystal domains. This sensitivity to small defects complicates fabricating devices with YBCO, and the material is also sensitive to degradation from humidity.
Applications in technology
Several commercial applications of high temperature superconducting materials have been realized. For example, superconducting materials are finding use as magnets in magnetic resonance imaging, magnetic levitation, and Josephson junctions.

   YBCO has yet to be used in many applications involving superconductors for two primary reasons:

First, while single crystals of YBCO have a very high critical current density, polycrystals have a very low critical current density for example, only a small current can be passed while maintaining superconductivity. This problem is due to crystal grain boundaries in the material: when the grain boundary angle is greater than about 5 degrees the supercurrent can't cross the boundary. The grain boundary problem can be controlled to some extent by preparing thin films via CVD or by texturing the material to align the grain boundaries.
A second problem limiting the use of this material in technological applications is associated with processing of the material. Oxide materials such as this are brittle, and forming them into wires by any conventional process doesn't produce a useful superconductor.
Finally, it should be noted that cooling materials to liquid nitrogen temperature is often not practical on a large scale, although many commercial magnets are routinely cooled to liquid helium temperatures.

The most promising method developed to utilize this material involves deposition of YBCO on flexible metal tapes coated with buffering metal oxides. Texture can be introduced into the metal tape itself (the RABiTS process) or a textured ceramic buffer layer can be deposited, with the aid of an ion beam, on an untextured alloy substrate (the IBAD process). Subsequent oxide layers prevent diffusion of the metal from the tape into the superconductor while transferring the template for texturing the superconducting layer. Novel variants on CVD, PVD, and solution deposition techniques are used to produce long lengths of the final YBCO layer at high rates. Companies pursuing these processes include American Superconductor, Superpower (a division of Intermagnetics General Corp), Sumitomo, Fujikura, Nexans Superconductors, and European Advanced Superconductors. A much larger number of research institutes have also produced YBCO tape by these methods.
Surface modification of YBCO
Surface modification of materials has often led to new and improved properties. Corrosion inhibition, polymer adhesion and nucleation, preparation of organic superconductor/ insulator/high-Tc superconductor trilayer structures, and the fabrication of metal/insulator/ superconductor tunnel junctions have been developed using surface modified YBCO.

   These molecular layered materials are synthesized using cyclic voltammetry. Thus far YBCO layered with alkylamines, arylamines, and thiols have been produced with varying stability of the molecular layer. It has been proposed that amines act as Lewis bases and bind to Lewis acidic Cu surface sites in YBa₂Cu₃O₇ to form stable coordination bonds.
Magnetic levitation
Similar to all superconductors, YBCO displays the Meissner effect as it's cooled and reaches its critical temperature. At the critical temperature and below, YBCO becomes perfectly diamagnetic and excludes all magnetic fields from passing through it by developing an internal magnetic field that perfectly balances the externally applied magnetic field. This internal field causes any magnet on the surface of the superconductor to levitate.
See full article Meissner Effect

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