8- superconducting critical temperature

Fig. 3.—The curve represents the calculated values of the superconductivity critical temperature. The circles are the experimental values for the elements and for binary alloys between adjacent elements.

Figure 7 Superconducting critical temperature as a function of x in Ba2YCusOx (58).

In 1908, Kamerlingh Onnes succeeded in liquefying helium, and this paved the way for many new experiments to be performed on the behaviour of materials at low temperatures. For a long time, it had been known from conductivity experiments that the electrical resistance of a metal decreased with temperature. In 1911, Onnes was measuring the variation of the electrical resistance of mercury with temperature when he was amazed to find that at 4.2 K, the resistance suddenly dropped to zero. He called this effect superconductivity and the temperature at which it occurs is known as the (superconducting) critical temperature, Tc. This effect is illustrated for tin in Figure 10.1. One effect of the zero resistance is that no power loss occurs in an electrical circuit made from a superconductor. Once an electrical current is established, it demonstrates no discernible decay for as long as experimenters have been able to watch ... 

We report in Fig. 13 the superconducting critical temperature Tc obtained by aluminium [143], carbon [183,184] and scandium [177] substitutions as a function of the superconducting gap ratio Aa/Aj,. The experimental results clearly show that the critical temperature increases by increasing the gap ratio as it was shown by theoretical calculations for a superlattice of wires in Fig. 8. In Fig. 13 we report the experimental ratio 2Aa /Tc and 2Ak/7 c for... 

Fig. 9. Correlation of superconducting critical temperature, Tc, vs. N, the number of naturally-occurring stable isotopes. The shaded curves should be considered only as showing the trend and the possibility of separating into two groups. The Tc data are obtained from Properties of Selected Superconductive Materials Natl. Bureau of Stand. Technical Note (1972). The number, N, is obtained from American Institute of Physics Handbook (McGraw-Hill Book Company, 1972. () - superconducting only under high pressure, - radioactive, and - represents more than one Tc for the same element under different physical environment.

Phase Equilibrium Diagrams - Constitution of Binary Alloys, M. Hansen (1958) R.P. Elliott (1965) and F.A. Shunk (1969), McGraw-Hill, New York Superconducting Critical Temperature Properties of Selected Superonducting Materials, B.W. Roberts, NBS Technical Note 724 (1972). 

Table 12.3 Superconducting Critical Temperatures Tc(Kelvin, at 1 bar) or Tc (Kelvin) at Applied Pressure P(kbar) for Selected Organic, Intercalated Graphite, (SN)X, and Fulleride Superconductors3...

Fig. 12.26. A plot of the maximum superconducting critical temperature with time showing, in addition, the important discoveries of the Meissner effect, the microscopic Bardeen, Cooper and Schrieffer (BCS) theory and the temperature barrier, set by the boiling point of liquid nitrogen. (Reproduced by courtesy of Dr. J.M. Bell,...

M. Rabinowitz, Quantum-gas model estimate for a wide range of superconducting critical temperatures. Intern. J. Theor. Phys. 28, 137-146 (1989). 

Table 3. Superconducting critical temperatures (/Kelvin, at 1 bar) or (/Kelvin, at applied pressure P/kbar) for organic, intercalated graphite, (SN),, and fulleride superconductors (updated from [71] TCE is 1,1,2-trichloroethylene BCDE is 1-bromo-1,2-dichloroethylene BDCE is 2-bromo-l,l-dichloroethylene DBCE is 1,2-dibromo-1-chloroethylene, TBE is 1,1,2-tribromoethylene).

Table I. Superconducting Critical Temperatures for the Samples Prepared in This Study as Determined by Resistivity vs.

TABLE I Crystallographic lattice parameters and superconducting critical temperatures (T for the La185Sr0.i5Cii1 xMxO4(M=Ni,Zn) and YBa2Cu3 xNix07 y series... 

The relation of sample preparation conditions, including oxygen concentration, annealing and hot isostatic pressing, to the superconducting critical temperature of the title materials is described. New synthetic materials are examined and characterized by a variety of techniques, including magnetic susceptibility measurements, ESR, electron microscopy and X-ray diffraction. 

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