Superconducting properties and mechanical strength of MgO fibres reinforced bulk Bi-2212 superconductor ceramics

摘要

Fabrication of bulk superconductors with optimum superconducting properties and stable mechanical behaviour is essential for the application of high-temperature superconducting ceramics in power engineering. In such application, high critical current density J_c and excellent mechanical stability are among the most important properties. In this study, 3-8 wt-%MgO fibres are added to Bi-2212 superconductor powder. The MgO fibres are prepared in-house using the sol-gel route. The Bi-2212/MgO fibres compounds are heat treated, followed by partial-melting and slow-cooling. The mechanical strength of the samples is studied by conducting the compression test. From the results, the addition of 5%MgO fibres is found to improve the texture of the Bi-2212/MgO fibres ceramics without degrading the transition temperature T_c if compared with the other samples. In addition, the J_c values are enhanced due to the addition of the MgO fibres that significantly improved the texture of the compounds and the grain connectivity within the grains. Significantly higher stiffness, strength and toughness are observed in MgO added samples at room temperature.