Transition elements high-temperature superconductors

Calculations using the methods of non-relativistic quantum mechanics have now advanced to the point at which they can provide quantitative predictions of the structure and properties of atoms, their ions, molecules, and solids containing atoms from the first two rows of the Periodical Table. However, there is much evidence that relativistic effects grow in importance with the increase of atomic number, and the competition between relativistic and correlation effects dominates over the properties of materials from the first transition row onwards. This makes it obligatory to use methods based on relativistic quantum mechanics if one wishes to obtain even qualitatively realistic descriptions of the properties of systems containing heavy elements. Many of these dominate in materials being considered as new high-temperature superconductors. 

Transition and rare earth metal oxides are the fundamental ingredients for the advanced smart and functional materials. Many functional properties of inorganic materials are determined by the elements with mixed valences in the structure unit [1], by which we mean that an element has two or more different valences while forming a compound. The discovery of high-temperature superconductors is a successM example of the mixed valence chemistry, and... 

A large number of metal alkoxides are available commercially (see Table 6.2). These are mostly the derivatives of main group or early transition elements M (III), M(rv), and M(V). The availability is dictated by request Thus, the derivatives of Al, Ti, and Zr are large-scale products offered by multiple producers. The alkoxides of rare earth elements became broadly available in the 1990s in connection with the studies of high-temperature superconductor materials, produced then in particular by sol-gel synthesis. Their accessibility strongly declined since then as they are used at the moment mostly as additives to luminescent materials and the desired quantities have apparently decreased. 

Soft metallic elements such as Al, In, Pb, Hg, Sn, Zn, Tl, Ga, Cd, V and Nb are type I superconductors. Alloys and chemical compounds such as Nb3Sn, V3Ga, and lZa3In, and some transition elements, are type II superconductors. Type II substances generally have a higher Tc than do type I superconductors. The recently discovered transition metal oxide superconductors have generated intense interest because they are type II superconductors with very high transition temperatures. Table 13.1 summarizes Tc for selected superconductors. 

Although several other types of exotic superconductors (e.g., organic superconductors, heavy-fermion f-electron superconductors, magnetically ordered superconductors, multinary rare-earth, actinide, and transition-metal superconductors) have been investigated intensely since 1986, the cuprate superconductors have received by far the most attention because the highest values of the superconducting critical temperature are found in this class of materials. Rare-earth and actinide elements are key constituents of many of the high-temperature cuprate superconductors and have played a prominent role in the development of the first and some of the more important cuprate superconductors. 

The observation of superconductivity at 18 K in Kj(C6o (Ref. 1) demonstrated the possibility of obtaining high superconducting transition temperatures in the doped fullerenes. In this paper we report the observation of superconductivity at 28 K on doping of Cso with rubidium. This transition temperature is dramatically higher than previously observed in any molecular, elemental, or in-termetallic superconductor, and is surpassed only by Bao.6Ko.4Bi03 and the cuprate superconductors. 

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