Precipitation from Gd/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub 7/ superconductor in low oxygen partial pressure

Precipitation behavior of second phases from Gd/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub 7/ solid solution was studied by processing in low oxygen partial pressure. With the decrease of solid solubility in the low oxygen partial pressure, Gd/sub 2/BaCuO/sub 5/ and CuO were precipitated from the solid solution as second phases. This resulted in an increase in the superconducting transition temperature up to that of GdBa/sub 2/Cu/sub 3/O/sub 7/ and an enhancement in the critical current density. The amount and size of the second phases can be controlled by the oxygen partial pressure, processing temperature and the starting composition, thus providing a useful method to introduce flux pinning centers for the improvement of critical current density.