Doping effects on the superconducting properties of bulk and PIT MgB2

A. SERQUIS; G. SERRANO

MgB2 Superconductor Research” Nova Science Publishers, Inc

Nova Science Publishers, Inc.

Lugar: Hauppauge NY; Año: 2008; p. 211 - 246

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. Here we first present a review of different kind of doping and substitutions in the superconducting properties of MgB2 bulk samples. In particular, we analyze the correlated enhancement of Hc2 and critical current densities Jc obtained by SiC,single (sw) or double (dw) wall carbon nanotubes (CNT) doping, to understand the role of C substitution and other defects in MgB2 superconducting properties.In second place we describe our recent progress in the processing, microstructures and superconducting properties of MgB2conductors prepared by PIT. Several sheath materials (stainless steel, copper and titanium) are used to fabricate SiC doped MgB2 wires and tapes. The microstructure and phase composition of the samples are followed by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-Ray Diffractometry (XRD). Critical temperatures (Tc), Jc and Hc2 are determined by magnetization and transport measurements. The correlation between the superconducting properties and the microstructural characteristics is discussed.