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

Abstract

Superconducting powders with nominal composition Bil.saPb0.~Srl.91Ca2.0aCu3.060 ~ were prepared by two different routes: by solid-state 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 rearrangements 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.