Superconductivity elements

Figure 4.11. Superconducting elements in the Periodic Table (adapted from Cheetham and Day...

Superconducting elements in the Periodic Table. A further example of the applications of the Table is shown in Fig. 4.11, where for the different elements an indication is given of their superconductivity behaviour. A correlation exists between this behaviour and the position in the Periodic Table. 

In the course of the broad research effort on preparing radically new superconducting materials, other inorganic systems were found to exhibit this phenomenon a sampling of these are presented below. The unusual feature of these materials is the fact that few contain "the best" superconducting elements in their chemical formulations. 

Figure 6.7 The superconducting elements. Reprinted, by permission, from I. Amato. Stuff, p. 68. Copyright 1997 by Ivan Amato.

Table 6.1 Critical Temperature and Critical Magnetic Field of a Number of Superconducting Elements...

Staff Range of CriticalTemperatures Observed for Superconductive Elements in Thin Films Condensed Usually at Low Temperatures, in Handbook of Chemistry and Physics, CRC Press, Boca Raton, Florida, 73rd Edition (1992-1993). 

The discussions in the informal and friendly atmosphere of Erice was on new experimental data showing that high Tc in doped cuprate perovskites is related with the nanoscale phase separation and the two component scenario, the two-band superconductivity in magnesium diboride and the lower symmetry in the superconducting elements at high pressure. 

Occurrence of superconductivity and the Tc associated with the superconducting elements have not been correlated with other physical attributes, such as atomic number, ionization potential, atomic orbital, crystal structure, etc. 

The second characteristic property called perfect diamagnetism means that the superconductor material does not permit an applied magnetic field B to penetrate into its interior. Those that totally exclude the applied magnetic field are known as Type I, and they are the superconducting elements such as tin, mercury, and lead, which have the respective transition temperatures 3.7, 4.1, and 7.2K. Other superconductors called Type II are also perfect conductors of electricity, but their magnetic properties are more complex. They totally exclude magnetic fields when the applied field is low, but only partially exclude them when the applied field is larger. Thus, in... 

Superconducting elements, as this comparison of motors demonstrates, make for a smaller and lighter shipboard engine. 

TABLE 2. Range of Critical Temperatures Observed for Superconductive Elements in Thin Films Condensed... 

Superconductivity is a rather common phenomenon in metals at low temperatures. In the rare earth group however, the only superconducting element at normal pressure is lanthanum. Most rare earth metals are magnetic due to their incomplete 4f shell. The magnetism inhibits the formation of Cooper pairs and thus inhibits superconductivity. Similarly, magnetism prevents superconductivity in the 3d-transition period beyond vanadium (cf. fig. 10.1). 

Tawe 294. Critical Temperature oe Superconductive Elements (sheet i oe 2)... 

A complete discussion of all the parameters causing premature quenching is beyond the scope of this paper. However, it appears that the major part of the problem is in the method of connecting superconducting elements together. Probably the resistance at the junction is so high that the I R loss heats the end of the superconductor above its transition temperature. As soon as a portion of the superconductor heats above its transition temperature, the I R loss in creases and the whole superconductor breaks down by heat conduction along the element. The most successful junctions have been made with a heli-arc welder, but these are still far from perfect. 

The BCS theory, however, developed in 1957 by three physicists, John Bardeen, Leon Cooper, and Robert Schrieffer, does estabhsh a model for the mechanism behind superconductivity. Bardeen, Cooper, and Schrieffer received the Nobel Prize in physics in 1972 for their theory. It was known that the flux quantum was inversely proportional to twice the charge of an electron, and it had also been observed that different isotopes of the same superconducting element had different critical temperatures. Actually, the heavier the isotope, the lower the critical temperature is. The critical temperature, in K, of an isotope with an atomic mass, M, expressed in kg.moT can be predicted by the following equation ... 

Figure 2 Superconducting tables in the periodic table. Superconductors at ambient conditions are noted in gray colour brown is used for superconducting elements at high pressure. No superconductivity has been reported for the rest of the elements...

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