Correlated enhancement of HC2 and Jc of carbon nanotube-doped MgB2

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

SUPERCONDUCTOR SCIENCE AND TECHNOLOGY

Institute of Physics (IOP)

Año: 2007 vol. 20 p. 12 - 15

0953-2048

The use of MgB2 in superconducting applications still awaits the development of a MgB2-based material where current-carrying performance and critical magnetic field are optimized simultaneously. We achieved this by doping MgB2 with double-wall carbon nanotubes (DWCNT) as a source of carbon in polycrystalline samples. The optimum nominal DWCNT content for increasing the critical current density, Jc, is in the range 2.5–10 at.% depending on field and temperature. Record values of the upper critical field, Hc2(4 K) = 41.9 T (with extrapolated Hc2(0) ≈ 44.4 T), are reached in a bulk sample with 10 at.% DWCNT content. The measured Hc2 versus T dependences for all samples are successfully described using a theoretical model for a two-gap superconductor in the dirty limit first proposed by Gurevich and co-workers.