Origin of the 110-K superconducting transition in the Bi-Sr-Ca-Cu-O system

Relationship between the TC of Smart Meta-Superconductor Bi(Pb)SrCaCuO and Inhomogeneous Phase Content

A smart meta-superconductor Bi(Pb)SrCaCuO (B(P)SCCO) may increase the critical transition temperature (T_C) of B(P)SCCO by electroluminescence (EL) energy injection of inhomogeneous phases. However, the increase amplitude ΔT_C (ΔTC=TC−TC,pure) of T_C is relatively small. In this study, a smart meta-superconductor B(P)SCCO with different matrix sizes was designed. Three kinds of raw materials with different particle sizes were used, and different series of Y₂O₃:Sm³⁺, Y₂O₃, Y₂O₃:Eu³⁺, and Y₂O₃:Eu³⁺+Ag-doped samples and pure B(P)SCCO were prepared. Results indicated that the T_C of the Y₂O₃ or Y₂O₃:Sm³⁺ non-luminescent dopant doping sample is lower than that of pure B(P)SCCO. However, the T_C of the Y₂O₃:Eu³⁺+Ag or Y₂O₃:Eu³⁺ luminescent inhomogeneous phase doping sample is higher than that of pure B(P)SCCO. With the decrease of the raw material particle size from 30 to 5 μm, the particle size of the B(P)SCCO superconducting matrix in the prepared samples decreases, and the doping content of the Y₂O₃:Eu³⁺+Ag or Y₂O₃:Eu³⁺ increases from 0.2% to 0.4%. Meanwhile, the increase of the inhomogeneous phase content enhances the ΔT_C. When the particle size of raw material is 5 μm, the doping concentration of the luminescent inhomogeneous phase can be increased to 0.4%. At this time, the zero-resistance temperature and onset transition temperature of the Y₂O₃:Eu³⁺+Ag doped sample are 4 and 6.3 K higher than those of pure B(P)SCCO, respectively.

High Tc Superconductors using Solution Techniques

We have investigated different solution techniques to synthesize the Cu-based superconductors in the thick film form. Thick films of YBa2Cu3O7 have been produced using controlled precipitation techniques. Bi-based and Tl-based materials have been deposited by spraying of ionic solutions. The numerous difficulties encountered during each process are analyzed in order to propose new synthesis procedures such as a new method, based on the precipitation of hydroxides only, which is described as a prospective for lowering the synthesis temperature and shortening the reaction time.