Doping and Nanotubes Addition Effects on the Superconducting Properties of MgB2

A. SERQUIS; G. SERRANO; B. MAIOROV; M. JAIME; F. BALAKIREV; G. PASQUINI; A. J. MORENO; L. CIVALE

Sydney, Australia

Conferencia; IUMRS-ICEM08 Symposium R: Superconductors, Electronic and Magnetic Materials; 2008

IUMRS

One of the most important issues for MgB2 magnet applications is the simultaneous enhancement of its critical current density (Jc) and the upper critical field (Hc2). Thus, on one hand, the pinning force may be improved by the incorporation of defects (nano particle doping, chemical substitutions, etc.). On the other hand, the doping level affects the intraband scattering coefficients and the diffusivity of the two bands of this peculiar superconductor, and these changes may cause a significant Hc2 variation. In particular, we analyze the correlated enhancement of Hc2 and critical current densities Jc obtained by SiC, single or double wall carbon nanotubes and titania nanotubes additions, to understand the role of C substitution and other defects in MgB2 superconducting properties of this material. The microstructure and phase composition of the samples are observed by Scanning Electron Microscopy (SEM) and X-Ray Diffractometry (XRD). Critical temperatures (Tc) and Jc are determined by magnetization and transport measurements. Four-probe transport measurements were performed using a 50 T pulsed magnet to determine Hc2(T). By means of magnetization was also studied the normalized time relaxation rate S=dlnJ/dlnt and pinning energy in the various samples. The different relations between the superconducting properties and the microstructural characteristics are discussed.