Obtención y propiedades superconductoras de granos tipo aguja basadas en el Bi(2212)

The grain size of a policrystalline sample is related with the critical current density (J c ) that it can transport. Increasing that grain size improves the J C value of the material and so its practical application possibilities. In this work we describe the obtainment of a needle-like superconducting microstructure based on Bi(2212). The size of these needles reached 100 μm in diameter and 1.5 mm in length in our last experiments. We also make a deep study of the formation steps for this microstructure (using an scanning electronic microscope (SEM)) and the changes in the composition of this microstructure during its formation. The superconducting properties are very promising: the critical current density (J c ) at 77.4 K and absence of magnetic field, is 2,300 A/cm 2 , and the magnetisation under a magnetic field of 50 G in an SQUID magnetometer shows T c =91 K. The measurement of the resistivity versus temperature, and the EDS analisys let us make a model for the composition of the needle-like grains.