High temperature superconducting ceramics

High temperature strength, 13 470 High temperature superconducting ceramic, 23 836-851... 

Evaporative decomposition erf solutions and spary pyrolysis have been found to be useful in the preparation of submicrometer oxide and non-oxide particles, including high temperature superconducting ceramics [819, 820], Allowing uniform aerosol droplets (titanium ethoxide in ethanol, for example) to react with a vapor (water, for example) to produce spherical colloidal particles with controllable sizes and size distributions [821-825] is an alternative vapor phase approach. Chemical vapor deposition techniques (CVD) have also been extended to the formation of ceramic particles [825]. 

Routes to monomeric , mononuclear , monolanthanide alkoxides, enolates, siloxides and aryloxides - an expanded title which will put the scope of the article in a more concrete form. The synthesis of mononuclear alkoxides, in particularly homoleptic derivatives [1], was decisively stimulated by the discovery of high temperature superconducting ceramics based on YBa2Cu307<, where yttrium represents the lanthanide elements [2]. The support of volatile and highly soluble molecular precursors is a prerequisite for synthesizing thin films of these materials by means of MOCVD [3] and sol gel processes [4], respectively. More recently, lanthanide alkoxide reagents became established in... 

Objects made of high-temperature superconducting ceramics include wires, cylinders, pellets, and tubes. (Photo courtesy of Argonne National Laboratory.)... 

YBCO Also known as 1-2-3, YBCO is an acronym commonly used to define the high-temperature superconducting ceramic yttrium-barium-copper oxide, the chemical formula of which has one yttrium, two barium, and three copper atoms (hence 1-2-3). 

During the years following the discovery of high-temperature superconducting ceramics in 1986 (Bednorz and Muller, 1986), highly exaggerated sales figures were promoted, in some cases with the clear expectation for scientists and... 

In the system Ba(Pb1.xBix)Os, the compound with x = 0.25 must be considered the first discovered ceramic material showing high-temperature superconductivity (7). Structure determinations have been carried out over the entire range of composition (8)-(ll) and the refined parameters are presented in Table 2. Superconductivity in this system exists only for values of x between 0.05 and 0.35. The value of the critical temperature increases with x, reaches a maximum value Tc 13K for x = 0.25, and then decreases. For x > 0.35, the material becomes a semiconductor. 

Challenges to Established Theories, It is interesting to note that some theoreticians struggle with describing how superconductivity occurs at high temperatures in the newer, ceramic superconductors. This is understandable because the classic theory of superconductivity is tied to metals. Most ceranuc superconductors discovered to date incorporate distinctive layers of copper and oxygen atoms, One question posed by some researchers, Is the mechanism of high-temperature superconductivity the same in hole superconductors as it is in electron superconductors ... 

Planar resonators - Equation (5.11) is not only valid for dielectric resonators. Any other type of electromagnetic resonator employing dielectric parts, like metal ceramic coaxial-type resonators (e.g. used as filters in mobile phones) and microstrip or coplanar resonators (used in microwave integrated circuits) have a Q-contribution due to dielectric losses. For the latter type of resonator the dielectric losses are negligible in comparison to metallic losses, unless high temperature superconducting metallization layers are applied. 

The discovery in 1986 of high-temperature superconductivity in ceramic cuprates of perovskite structure started a period of very intensive research of transition metal oxides. Soon afterwards, in 1993, the colossal magnetoresistance effect was discovered in manganite perovskites, again leading to an increasing research activity in the field of magnetic oxides. It is... 

The biggest explosion in materials chemistry and physics occurred in late 1986 when high-temperature superconductivity was discovered in a lanthanum cuprate, a material which was a ceramic and on which a few chemists had worked earlier. As stated in a report of the US National Academy of Sciences, this discovery changed the role of chemistry in the study of materials, and materials chemistry became a more significant part of materials science. It is around this time that even chemists started to consider solid state chemistry as an integral and important part of main-stream chemistry. 

Physicochemical properties of high-temperature superconductive complex oxides are substantially dependent on synthesis conditions, in particular, on homogeneity of the mixture of finely dispersed components. Mechanical activation allows to improve the ceramic technology of their preparation, in particular, YBa2Cu307 and YBa2Cu408. where x and y are parameters characterizing the lack of oxygen. 

SUPERCHAINS AND PLANES. The atomic structure of ceramic superconductors contains chains and planes of copper and oxygen atoms. Both chains and planes appear to contribute to high-temperature superconductivity in some of the new materials. (Courtesy Argonne National Laboratory.)... 

But things can be better, and the taming of high-temperature superconductivity will assure that. We have seen how the new ceramics would affect the power, transportation, medical, defense, and electronics industries. The commercial applications will without question have a revolutionary impact on society. And, perhaps, the most important impacts have not yet even been anticipated. 

These "high-temperature" superconducting materials are very interesting. First, they are not metals. They are ceramics. A ceramic is a clay-like material. It often consists of sand, clay, brick, glass, or a stone-like material. 

In the fifteen years since publication of the first edition of Comprehensive Coordination Chemistry (CCC, 1987), group 5 chemistry has been part of the intensive development of ceramic, optical, and magnetic materials based upon metal borides, nitrides, phosphides, oxides, and sulfides. A major impetus came from the discovery of the high-temperature superconducting oxides. In addition, the search for new routes to these materials via sol-gel or chemical vapor deposition techniques has spurred growth in metal amido, oxo, alkoxo, thio, and carboxylato chemistry. 

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