Anisotropic thermal and mechanical properties of bulk high-Tc Bi-based superconductors

Superconducting powders with nominal composition Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06Ox were prepared by two different routes: by solid-sate reaction of the respective oxides and carbonates and by pyrolysis of organic precursors. Highly dense superconducting specimens characterized by textured microstructure were prepared by hot pressing. The thermal-expansion coefficients of different typologies of samples were measured by dilatometric tests in both directions parallel and perpendicular to the pressure application direction. Structural rearrangement s occurring during thermal treatments were studied. As regards mechanical characterization, microhardness, flexural strength and fracture toughness were evaluated and related to the microstructure anisotropic degree of the sample.