The best performance superconductor should have the highest Jc, and Hirr and the lowest surface resistance Rs at 77 K. Our original superconductor CuBa2Ca3Cu4O12-y (Cu-1234) has a high Tc &gt
117 K (= one and a half times of 77 K) even in over-doping state, a low superconducting anisotropy (γ = 1.6), a long coherence length along c-axis (ξc = 1 nm) and a small penetration depth (λc = 220 nm). Therefore, it is capable of becoming the best performance superconductor with a high Jc {50 MA/cm2 (77 K, 0 T), 0.5 MA/cm2 (77 K, 10 T)}, a high Hirr {30 T (77 K)}and a low Rs {30 μΩ (77 K, 10 GHz)}. These superconducting properties are derived from its unique composition, lattice structure and electronic structure. The prediction is going to be proved with the experimental data of Tc, Jc, Hirr and hole concentration, NMR, specific heat and photoemission measurements and band calculation. Sustainable high Tc (&gt
117 K) in over-doped Cu-1234 were achieved by the selective over-doping effect, and high Tc's of 126 K in Cu1-xTlx-1234 and 132 K in Cu1-xTlx-1223 were achieved by homogeneous optimum-doping effect by band structure engineering. The results show the effectiveness of band theory and Fermi liquid theory for approaching to the best performance superconductor from over-doping side. The two kinds of superconducting transitions at Tc = 117 K and Tc2 = 60 K have been observed for over-doped Cu-1234 by NMR and specific heat measurements indicating the weak coupling of two superconducting-order-parameters (d + is or d + id). These weak-coupling two order parameters in Cu-1234 are expected to contribute to the enhancement of superconducting performance. A new self-assembling epitaxy (SAE) techniques for the preparation of Cu(Tl)-1234 and -1223 thin films has been developed by combining Tl-1234 self-assembling effect and amorphous phase epitaxy (APE) effect. The thin films of Cu1-xTlx-1223 (x ∼ 0.5) have achieved a high Jc = 20 MA/cm2 (77 K, 0 T) and Jc = 0.4 MA/cm2 (77 K, 10 T), and its data extrapolate a high (Hirr)ab ∼ 30 T at 77 K. © 2001 Elsevier Science B.V. All rights reserved.