Akademik Veri Yönetim Sistemi
Journal of Materials Science: Materials in Electronics, cilt.23, sa.11, ss.1965-1970, 2012 (SCI-Expanded)
This study deals with not only investigate the effect of the copper diffusion on the microstructural and superconducting properties ofMgB 2 superconducting samples employing dc resistivity as a function of temperature, scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements but also calculate the diffusion coefficient and the activation energy of copper for the first time. Electricalresistivity measurements indicate that both the roomtemperature resistivity value and zero resistivity transition temperatures (Tc) increase with increasing the diffusionannealing temperature from 650 to 850 °C. SEM measurements show that not only the surface morphology and grain connectivity improve but also the grain size of the samples increases with the increase in the diffusion-annealing temperature up to 850 °C. As for the XRD results, all the samples contain the MgB2 phase only and exhibit the polycrystalline superconducting phase with more intensity of diffraction lines, leading to the increasement in the lattice parameter a and c. Additionally, the diffusion coefficient is observed to increase from 6.81 × 108 to 4.69 × 10-7 cm2 s-1 as the diffusion-annealing temperature increases, confirming that the Cu diffusion at lower temperatures is much less significant. Temperature dependence of the Cu diffusion coefficient is described with the aid of the Arrhenius relation D = 3.75 × 10-3 exp (-1.15 ± 0.10 eV/kBT) and the corresponding activation energy of copper inMgB2 systemis found to be about 1.15 eV. The possible reasons for the observed improvement in microstructural and superconducting properties of the samples due to Cu diffusion are also discussed. © Springer Science+Business Media, LLC 2012.