Superconductivity of nano-TiO2-added MgB2

✍ Scribed by H. Kishan; V.P.S. Awana; T.M. de Oliveira; Sher Alam; M. Saito; O.F. de Lima

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 854 KB
• Volume: 458
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/j.physc.2007.02.014

✦ Synopsis

We report on the synthesis, phase formation, microstructure, and magnetization, of nano(n)-TiO 2 -added MgB 2 polycrystalline compounds. The added n-TiO 2 amounts are varied from 1% to 15% in weight (wt). All the studied samples are near single phase with small amounts of un-reacted Mg/MgO up to 10 wt%. The 15 wt% n-TiO 2 added sample seems to be a multi-phase compound with unusual broadening of the main MgB 2 reflection and additional unidentified lines in its X-ray diffraction (XRD) pattern. The superconducting transition temperature (T c ), as measured by magnetization experiments, decreases marginally with n-TiO 2 addition, for example the T c s are at 37.5 K and 35.5 K, respectively, for pristine and 10 wt% n-TiO 2 -added samples. This indicates that Ti has not significantly substituted into the host MgB 2 lattice. The grain morphology of these compounds reveals porous regions and does not change much with TiO 2 addition. High resolution transmission electron microscopy (HRTEM) studies revealed the presence of n-TiO 2 in these samples. The critical current density (J c ) of the MgB 2 -n-TiO 2 samples, as estimated using the Bean model, shows better performance under magnetic fields above 3 T than pristine MgB 2 for up to 4 wt% of addition, and decreases rapidly for additions above 6 wt%. We conclude that n-TiO 2 helps in enhancing the flux pinning centers in MgB 2 superconductor and hence improves the J c (H) performance for additions up to 4 wt% in fields above 3 T.