Comparison of the oxalate co-precipitation and the solid state reaction methods for the production of high temperature superconducting powders and coatings

摘要

High quality orientated YBa_2Cu_3O_(7-x) (x = 0.1-0.2) (YBCO) superconducting coatings were produced by the electrophoretic deposition technique. The fine particle YBCO powder used, was produced by the oxalate co-precipitation method on Au/Si and Pt/Si wafers. The optimized thermal treatment for both, powders and coatings, was followed by thermal analysis (thermogravimetry (TG) and differential scanning calorimetry (DSC)). The powders and coatings obtained, were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), optical microscopy, magnetic susceptibility and electrical resistivity measurements. It resulted that by the oxalate co-precipitation method finer and more homogeneous nanocrystalline YBCO powders were produced in comparison to the solid state reaction method, leading to more favorable conditions for their thermal treatment, like lower sintering temperature and shorter duration of the sintering process, as well as better superconducting properties, expressed by the shape and value of the corresponding magnetization curves. Furthermore, the production of the coatings was achieved in a shorter electrophoresis time by the powders from the co-precipitation method and the coatings produced were orientated having improved superconducting properties in comparison to those obtained by the solid state reaction method.