Polymerized complex synthesis of a pure 93 K Y₂Ba ₄Cu₇O_15-d superconductor without the need of high oxygen pressure and additive catalysts

High-purity ceramic material of the superconducting phase Y ₂Ba₄Cu₇O_14.82 (247) has been synthesized at 870°C by the polymerized complex method using neither high oxygen pressure nor additive catalysts. The method is based on the formation of a polymer-metal complex precursor which is prepared through polyesterification between metal citrate complexes and ethylene glycol. Apart from the fact that high oxygen pressure is unnecessary, the present preparation technique offers more convenient and easier fabrication of highly pure 247 material compared with other wet chemical routes since it eliminates many steps such as centrifugation, filtration, aging, and pH control. X-ray diffraction and Raman scattering analyses show that the material is single-phase without any indication of secondary phases. Zero-resistance has been achieved at 88.0 K with a transition width narrower than 4 K. Complex ac magnetic susceptibility measurements confirm the presence of a single bulk superconducting 247 phase with T_c(onset)=93.0 K and ΔT_c (10%-90%)=4.5 K.