ENHANCEMENT IN FLUX-PINNING AND IRREVERSIBILITY FIELD BY MEANS OF A SHORT-TIME ANNEALING TECHNIQUE FOR HGBA2CA2CU3O8.4 SUPERCONDUCTOR

We have successfully prepared mercury-based high-temperature supercond uctors of composition HgBa2Ca2Cu3O8+delta by means of the encapsulatio n and short-time annealing technique. By measuring the hysteresis loop s, the critical current density J(c) is determined by using Bean's mod el. Scaling behaviours of the pinning-force density are discussed. By using the short-time annealing technique, the irreversibility line and the flux-pinning properties of the Hg-1223 specimen were enhanced by the introduction of more lattice defects, such as screw dislocations, intergrowth structures and stacking faults, into the Hg-1223 specimen. Furthermore, it is shown that the temperature dependence of the irrev ersibility line H-irr exhibits different features within two temperatu re regions. In the low-temperature region H-irr is proportional to [1- (T/T-c)(2)](6.3), while in the high-temperature region H-irr is propor tional to [1-(T/T-c)(2)](1.5). The observed H-irr can be clarified by comparison with the theoretical model.