Microstructural and mechanical characterization of bulk BSCCO (2223) superconductor

Bi_1.84Pb_0.34Sr_1.91Ca_2.03 Cu_3.06O_x bulk superconductor was prepared by hot pressing and pressureless sintering reaching relative density values in the 96-99 and 85-90% range, respectively. The hot-pressed specimens exhibited a textured microstructure with the "c"-axis preferentially aligned parallel to the direction of sintering pressure application, while the plastic flow into the particles, during hot pressing, favours the grain growth in the direction perpendicular to the pressure application. Both density and microstructure texturing results were greatly influenced by sintering temperature and pressure. More specifically for pressureless sintered samples, high cold uniaxial pressure was first applied to prepare highly dense green bodies characterized by unusually high degree of texture orientation. They were subsequently pressureless sintered to form links between grains by the activation of diffusion process and partial melting at the grain boundary. Mechanical characterizations, supported by microstructural evaluations, underline the anisotropic character of the material, its intrinsic brittleness and the low hardness.