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We present measurements of the magnetization hysteresis on neutron-and proton-irradiated YBa2Cu307 z single crystals. The crystals were irradiated to Auences of 2X 10' n cm (E")0. 1 MeV) and 1X10' p cm (E~=3.5 MeV), respectively. The magnetization was measured for both field directions. We observed increases of the hysteresis by a factor of 5 at 10 K and 1 T for H~~c for the neutronirradiated sample and a factor of 9 for the proton-irradiated sample. For H~~ab the hysteresis increased by a factor of 8 and 6, respectively. The irradiated crystals were annealed at 100, 200, and 300'C in air for 8 h each. The irradiation-induced decrease of T, is fully recovered after the final annealing step for both types of irradiation. The magnetization hysteresis for H~~ab decreases almost to its preirradiation level after annealing at 300'C for both types of irradiation. In contrast, for H~~c, 50% of the initial neutron-irradiationand 30% of the proton-irradiation-induced enhancements of the magnetization hysteresis are still maintained after the final annealing. The differences in annealing between neutron-and proton-irradiated samples are attributed to the different amount of point defects created by these types of irradiation.

For Bi 2 Sr 2 CaCu 2 O y (2212), it is shown that an oxygen gradient, as opposed to a temperature gradient, can be used to produce large bulk forms of the 2212 superconductor with highly textured microstructures from an oxygen-deficient melt held at a constant temperature. Material produced in this manner was found to have transition temperatures between 85 and 92 K, high critical current densities below 20 K, and modest critical current densities at 77 K.

The solidification processes for the compositions Bi 2 Sr 2 CaCu 2 O y (2212) and Bi 2 Sr 1.75 Ca 0.25 CuO y (2201) were determined as a function of oxygen partial pressure. During solidification in argon, the superconducting phases were generally not observed to form for either composition. The solidification processes for the compositions Bi2Sr2CaCu20y (2212) and Bi2Sri.75Cao.25CuOy (2201) were determined as a function of oxygen partial pressure. During solidification in argon, the superconducting phases were generally not observed to form for either composition. In both cases, the solidus is lowered to approximately 750 °C. Solidification of Bi2Sri 75Ca0.25CuOy in Ar resulted in a divorced eutectic structure of Bi2Sr2_A:Cax0>, (22JC) and Cu2O while solidification of Bi2Sr2CaCu20>, in Ar resulted in a divorced eutectic structure of Bi2Sr3_xCa;c03, (23x) and Cu2O. Solidification of Bi2Sri.75Cao.25CuOy in O2 resulted in large grains of 2201 interspersed with small regions containing the eutectic structure of 22* and CuO/Cu2O. Solidification of Bi2Sr2CaCu2Oy in partial pressures of 1%, 20%, and 100% oxygen resulted in multiphase samples consisting of 2212, 2201, some alkaline-earth cuprates, and both divorced eutectic structures found during solidification in Ar. For both compositions, these latter structures can be attributed to oxygen deficiencies present in the melt regardless of the overpressure of oxygen. These eutectic structures are unstable and convert into the superconducting phases during subsequent anneals in oxygen. The formation process of the 2212 phase during solidification from the melt was determined to proceed through an intermediate state involving the 2201 phase.

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