Superconducting properties of MgB2 with addition of other AlB2 type diborides and carbon sources, prepared using high energy ball milling and HIP

L. B. S. DA SILVA; V. C. VELLOSO METZNER; G. SERRANO; A SERQUIS; E. HELLTROM; D. RODRIGUES JR.

La Haya

Conferencia; Superconducting Centennial Conference EUCAS-ISEC-ICMC 2011; 2011

EUCAS-ISEC-ICMC

Magnesium diboride (MgB2) is one of the most promising superconductors for practical applications, due to its properties and characteristics, and to the low price of the precursor elements. The application can be enhanced with the improvement of the superconducting properties. The operation temperature can be kept by cryocoolers around 20K. In this work, additions of other diborides with the same crystal structure of MgB2 and some carbon sources (SiC, graphite, and carbon nanotubes) are studied, in an attempt to improve the superconducting properties of the material via doping and simultaneously creation of new pinning centers in the superconducting matrix. To reduce the problem with weak links and to improve the densification and intergrain connectivity, high energy ball-milling and hot isostatic pressing (HIP) were used. Magnetic measurements using SQUID were performed to analyze the superconducting phase. X-ray diffraction was used to determine the formation of new phases and verify the doping in the superconducting phase. The pinning mechanisms acting in the samples could be verified through the curves of volumetric pinning force versus applied magnetic field, using the Dew-Hughes approach. Scanning and transmission electron microscopy (SEM and TEM) were performed to analyze the distribution and the size of phases formed during the preparation. TEM was also used to analyze the MgB2 grain boundaries, fundamental to determine the pinning mechanisms acting in the material.