Intragranular and intergranular superconducting properties of bulk melt-textured YBCO

We have investigated the superconducting properties of bulk melt-processed YBCO using different experimental techniques. First, single domain material s (i.e. containing no grain boundaries) have been studied. Electrical resis tivity, current-voltage characteristics, M-H loops, and A,C. susceptibility . have been measured for different field and current directions. The intrag ranular properties are characteristic of high-quality melt-processed YBCO m aterial,,vith a critical current density J(c)(T=77K, B=1T//c) > 10(4) A/cm( 2). The anisotropy ratio J(c)(ab)/ J(c)(c) is found to be close to 3. Both magnetic and transport measurements show that defects in the microstructure do not significantly impede the current flow inside the single domain. The se results were compared to those measured on samples containing one "natur al" single grain boundary which sometimes appears during the grain growth p rocess. The intergranular properties show a much stronger current and magne tic field dependence than that measured within the grain and these differen ces are discussed.