Crystallographic texture study of nano-SiC-doped MgB2 wires

MELONE MAURO; MORÁN MAURICIO; MALAMUD FLORENCIA; MALACHEVSKY MARÍA TERESA; SERQUIS ADRIANA

Conferencia; APPLIED SUPERCONDUCTIVITY CONFERENCE; 2020

MgB2 superconductor has great potential for technological applications based on its critical temperature (Tc=39 K), low cost of the raw materials, chemical simplicity, and absence of weak-link limitations to the critical current density (Jc) [1]. Its hexagonal crystallographic structure (space group P6 /mmm) presents a two-band gap. This gives a low anisotropy in the critical field (Hc2) when compared with high-Tc compounds [1]. Even though, this Hc2 anisotropy has an impact on the Jc [2], making it several times higher along the ab plane than in the c direction. It is well-know Jc can increase up to 100 times by adding small amounts of nano-SiC, due to carbon doping in the MgB2 structure and the formation of nano-Mg2Si precipitates that behave as pinning centers [1]. In this case, Jc anisotropy may be modified, since carbon doping affects the two-band gap energy [3]. Some of this knowledge is used in Powder-in-Tube (PIT) wires, which is the most employed method. Several studies report a crystallographic anisotropy of PIT-tapes and its influence on the Jc [4]. Nevertheless, none of them studied the crystallographic texture of nano-SiC-doped wires made by drawing. This study could provide useful information to improve the final products. In this work, we prepared Ti sheathed MgB2 wires by PIT with two different cross-sections: one circular and one hexagonal. We employed Grade 2 Ti and a mixture of 95 at % MgB2 (325 mesh, Alfa Aesar) and 5 at % SiC (20-30 nm) to assemble two superconducting PIT wires. Diameter reduction proceed by wire drawing, with some intermediate short annealing time. We analyzed the drawing effect on the crystallographic texture of both the Ti sheath and the MgB2 core using X-ray diffraction (XRD) pole figures. We evaluated the critical current density of the wires in two different directions using a SQUID magnetometer. We finally studied the influence of the mechanical deformation on the crystallographic texture and the superconducting properties, assessing the use of different dies in the process.