Electrical and magnetic studies of YBa2Cu3O7:Y2BaCuO5 composites

The superconducting and normal-state properties of YBa 2 Cu 3 O 7 :Y 2 BaCuO 5 composites with varying mass ratios and final sintering temperatures were investigated by using electrical resistivity and AC susceptibility techniques. By increasing the Y 2 BaCuO 5 concentration, the normal-state resistivity of the composites changes from a metallic-like behavior to a semiconducting-like behavior. Although the onset temperature of the superconductivity was unaffected by the presence of Y 2 BaCuO 5 , the zero-resistance temperature decreased with increasing Y 2 BaCuO 5 content. Increasing the Y 2 BaCuO 5 fraction also leads to a stronger AC magnetic field dependence, implying weaker intergranular coupling. By increasing the final sintering temperature from 900°C to 1050°C, the intergranular coupling can be improved. These results indicate that the presence of insulating Y 2 BaCuO 5 does not affect the intrinsic superconducting properties of the YBa 2 Cu 3 O 7 grains but has a strong effect on the intergranular coupling.