SUPERCONDUCTOR SCIENCE & TECHNOLOGY, cilt.18, ss.82-86, 2005 (SCI İndekslerine Giren Dergi)
Samples of YBa2Cu3O7-delta, having about 30% Y2BaCuO5, were prepared with a melt-process method by adding B2O3 up to 0.5 wt% to the oxides. The structural and superconducting properties of the samples were studied by x-ray diffraction, x-ray fluorescence, scanning electron microscope, magnetization and magneto-optic techniques. B2O3 additions during the melt-processing enlarge intergrain regions that weaken the conduction links between the grains. T-c drops by 1.0-6.0 K, and at 50 K J(c) decreases from about 1.6 x 10(4) to 1.8 x 10(3) A cm(-2) with B2O3 additions up to 0.5 wt%. A secondary peak was observed in the J(c) versus field plot of the boron-free sample that decreases with boron additions. At 50 K the intragrain J(c) values of the boron-free sample were about 12% higher than the intergrain J(c) value, and such differences increase with B2O3 additions. These observations, together with the enlargements of the intergrain regions with B2O3 additions, suggest that most of the boron atoms take part and reside at grain boundaries.