Synthesis and characterization of YBa2Cu4O8 high transition temperature superconductor powders from xerogel precursors

After succeeding in the preparation of YBA2Cu3O7 high Tc superconductors powders using the xerogel method, the next logic step was to scale the technique to the related and difficult to synthesize, but environmentally stable, YBa2Cu4O8(1,2,4). The xerogel precursor was as simple to prepare as the original YBCO xerogel, by means of the same metal salts-gelling agent system. Extensive heat treatment research was done using a combination of X-ray diffraction and TGA analysis to determine the best temperature profile to obtain the superconducting powders. The features and comparison between a single step and a multiple step calcination procedure are discussed. The results of this synthesis are as encouraging as the one presented for the YBCO. XRD of the xerogel shows non large range scattering. The XRD shows a phase purity above 99% which is congruent with the linear behavior of the product in TGA analysis up to the 1,2,4 decomposition temperature. Critical temperature of the final product is 80 K, and the material shows a large magnetic field dependence (low Maissner effect). The particle size of the superconducting powders is smaller than 0.3 microns