Effects of silver addition on reaction diffusion in YBCO composite thick film

The temperature dependence of electrical resistivity of YBa2Cu3 O7-x/Ag composite thick films is studied. The films are prepared by reaction diffusion between a high melting point Y2BaCuO substrate and low melting point Ba3Cu5O8 coating layer. Addition of Ag2O to the coating layer aided diffusion and formed a laminated layer composed of Ag and the superconducting layer on top of the substrate. The granularity parameters such as weak link resistivity ρwl and percolative conduction factor α arising due to current frustration caused by misalignment of grains and sample defects like voids and cracks are estimated from residual resistivity, ρo and slope of the curves dρ/dT. Ag is shown to significantly modify microstructure in YBCO/Ag composites in terms of drastic reduction of weak link resistivity and provide better alignment of anisotropic YBCO grains. (author)