DESTRUCTION AND RECOVERY OF SUPERCONDUCTIVITY IN BI-PB-SR-CA-CU-O SYNTHESIZED UNDER HIGH-PRESSURE

The high-T(c) superconductors (Bi, Pb)2Sr2Ca2Cu3Ox (2223 phase) are hot-pressed from the superconducting powder-mixtures under high pressure up to 5.4 GPa. Although the as-pressed sample synthesized under 40 MPa shows superconductivity, the as-pressed sample synthesized under 5.4 GPa does not. The as-pressed sample synthesized under 5.4 GPa consists of a mixture of an unknown phase and the 2223 phase having a longer c-lattice parameter (2223'). Microscopic structures of the pressed samples are examined by high-resolution transmission electron microscopy. In the as-pressed samples, curved c-planes, which are caused by high pressure, are observed. In the 2223' of the as-pressed sample synthesized under 5.4 GPa, the c-planes are particularly heavily distorted. Recovery of the microstructures and superconductivity occurs through annealing.