INVESTIGADORES
SERQUIS Adriana Cristina
congresos y reuniones científicas
Título:
Effects of doping on the superconductivity of MgB2
Autor/es:
A SERQUIS
Lugar:
Rio de Janeiro
Reunión:
Conferencia; Avanços e Perspectivas da Ciência no Brasil, América Latina e Caribe; 2007
Institución organizadora:
Brazilian Academy of Sciences - TWAS
Resumen:
The strong potential
for commercial applications of MgB2 is due to a unique combination
of characteristics, such as a high transition temperature Tc~39K, chemical
simplicity, lightweight and low cost of the raw materials. In addition, the
absence of weak-link behavior at grain boundaries in polycrystalline samples
allows the use of simple Powder In Tube (PIT) methods to fabricate wires and
tapes. 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 I will 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 I will describe our recent
progress in the processing, microstructures and superconducting properties of
MgB2 conductors prepared by PIT. Several sheath
materials (stainless steel, copper and titanium) are used to fabricate SiC and
carbon nanotubes (CNT) doped MgB2 wires and tapes The microstructure
and phase composition of the conductors are followed during the deformation and
heat treatment processes by Scanning Electron Microscopy (SEM) 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.