PREPARATION OF HIGH-DENSITY YBA2CU3OX CERAMICS WITH IMPROVED SUPERCONDUCTING PROPERTIES BY HOT-PRESSING UNDER CONTROLLED-ATMOSPHERE

High-density YBa2Cu3Ox (relative sintered density ≥97%, as hot pressed) ceramics with an improved superconducting temperature (Tc) of 95 K and a critical current density (J c) of 700 A/cm2 at 77 K, 0 T have successfully been produced by using hot pressing under a carefully controlled ambient gas system, followed by an appropriate oxygenation process. The obtained results indicate that in the oxygenation process of an YBa2Cu3Ox crystal the phase transition from the tetragonal phase (nonsuperconducting) to orthorhombic I phase (Tc≥90 K) occurs much easier than from orthorhombic II phase (Tc≊60 K) to orthorhombic I phase. This may also demonstrate a possible solution to the oxygenation problem in high-density YBa2Cu3Ox ceramics usually with degraded superconducting properties.