Chemical Synthesis and Characterization of Superconducting YBa 2 Cu 4 O 8 at Ambient Pressure

A monophasic high‐T c superconductor YBa 2 Cu 4 O 8 with T c(onsel) , 80 K and fine 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 YBa 2 Cu 4 O 8 superconductor. The effect of temperature of preparation and precursor compositions (i.e. EG/CA molar ratio) on the purity and superconductivity of the YBa 2 Cu 4 O 8 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 YBa 2 Cu 4 O 8 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 YBa 2 Cu 4 O 8 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 films.