HIGH-TEMPERATURE DEFORMATION AND FRACTURE OF BI-SR-CA-CU-O SUPERCONDUCTORS

Dense polycrystalline Bi2Sr2CuOx (2201), Bi2Sr2CaCuOx (2212), and (Bi, Pb)2SrCa2Cu3Ox (2223) specimens were compressed in air at 730-835-deg rees-C. All of the materials exhibited an apparent steady-state creep response. Strain rate was proportional to stress to the 3.1-3.8 power. Apparent activation energies for the deformation processes were 520 /- 50 kJ/mole for the 2201, 630 +/- 210 kJ/mole for the 2212, and 960 +/- 210 kJ/mole for the 2223. Transmission electron microscopy reveale d substantial generation and propagation of basal-plane dislocations d uring deformation. Few nonbasal-plane dislocations were observed. Inte rgranular fracture was evident in all deformed samples, and intragranu lar fracture was evident along the basal planes of some grains. It is suggested that the kinetics of fracture were determined by dislocation motion within the grains.