錯体重合法によるY₂Ba₄Cu₇O_14+dの1気圧酸素雰囲気下での合成

抄録

High-purity ceramic sample of the superconducting Y₂Ba₄Cu₇aO_14.82 (247) phase has been prepared at 870°C by the polymerized complex method using neither high oxygen pressure nor the additive catalysts. The method is based on the formation of a polymer complex which is obtained through polyesterification between metal citrate complexes and ethylene glycol. Apart from not requiring high oxygen pressure, the present preparation technique offers more convenient fabrication of highly pure 247 compound compared with other wet chemical routes since it eliminates many steps such as aging and pH control. X-ray diffraction and Raman scattering analyses have shown that the material is virtually of single-phase without any indication of secondary phases. Zero resistance has been achieved at 88.0K with a transition width narrower than 4 K. Complex magnetic susceptibility measurements have confirmed the presence of a single bulk superconducting 247 phase with Tc(onset)=93.0 K and ΔTc(10-90%)=4.0 K.