Factors influencing the critical current of Y-Ba-Cu-O superconductor

Effects of doping V on the superconducting oxide YBa{sub 2}Cu{sub 3{minus}{ital x}}V{sub {ital x}}O{sub {ital y}} have been studied. It was found that when {ital x}{le}0.6, there is a decrease, in the superconducting phase ratio of volume to the size of grain and an increase in {ital J}{sub {ital c}}, mass density and hardness of the samples, whereas the sample synthesis conditions, critical temperature {ital T}{sub {ital c}} and superconducting phase structure are not sensitive to the {ital x} values. These suggest that the impurity V stays mainly on the grain boundaries and can improve the connection between the grains considerably. In certain cases, it is more important to improve the grain connection than to increase the superconducting phase ratio.