CHEMICAL SYNTHESIS AND CHARACTERIZATION OF SUPERCONDUCTING YBA2CU4O8 AT AMBIENT-PRESSURE

A monophasic high-T-c superconductor YBa2Cu4O8 with T-c(onset) 80 K and fme grain size has beeen synthesized under oxygen at 1 bar employing metal-ethandiol/citric acid (EG/CA) polyester complex precursors. In addition to the preparation, we report the results of infrared (IR) spectra, thermogravimetric analysis (TGA), and X-ray diffraction (XRD) relevant to preparation of the YBa2Cu4O8 superconductor. The effect of temperature of preparation and precursor compositions (i.e. EG/CA molar ratio) on the purity and superconductivity of the YBa2Cu4O8 compound was investigated. The temperature dependence of resistivity and normal-state resistivity of the samples varied systematically with the EG/CA ratio in the precursors. T-c(onset) and the width of the superconducting transition for YBa2Cu4O8 samples were determined to be 80 K for all samples and 6 - 9 K, respectively; the latter depended on the corresponding EG/CA ratios in the precursors. The Meissner fraction of YBa2Cu4O8 samples determined from dc magnetization tests was independent of the EG/CA ratio. Polyester precursors can potentially be applied in large-scale preparation of high T-c ceramic-oxide superconductors and superconducting thin firms.