No abstract

Dense (Bi, Pb), Sr,Ca,Cu,O, bars were fabricated by sinter forging. The bars were highly phase-pure and exhibited strong textures in which t h e c axes of the platelike grains were preferentially aligned parallel to the pressing direction. Transport critical current densities increased with texture, reaching a maximum of 8 x io3 A cm-2 at 77 K in a seif-field. Optimal processing in air occurred at 845-850 "C.

No abstract

Very dense Bi,Sr,CaCu,O, bulk specimens were fabricated by hot isostatic pressing or sinter forging. The specimens exhibited textures in which the c-axes were aligned preferentially perpendicular to the top and bonom faces. Fracture toughness was found to be dependent on orientation, with the values ranging from 2.7 to 3.9 MPaThe average Vickers hardness for the specimens was ~7 0 0MPa. Elastic anisotropy determined by velocity of sound measurements was consistent with textures determined by x-ray diffraction.

YBa 2 Cu 3 O x was deformed from 850 to 980 °C in oxygen partial pressures of 10 3 to 10 5 Pa. Steady-state creep rate, e, for P(O 2 ) from 10 4 to 10 5 Pa could be expressed as e = Aa yo (GS)" 28±06 exp -(970 ± 130 kJ/mole)/R7; where A is a constant, a-the steady-state stress, GS the average grain size, and R and T have their usual meanings. For P(O 2 ) from 10 3 to 3 x 10 3 Pa, the activation energy decreased to about 650 kJ/mole and for a given temperature creep kinetics were much faster. The data and microscopic observations indicated that creep occurred by diffusional flow. Comparisons with diffusion data for YBa 2 Cu 3 O;E suggested that Y or Ba may be rate-controlling diffusing species.