Portal de Periódicos da CAPES

Effects of heat treatment temperature on the formation of MgB 2 bulk superconductors prepared using MgB 4 and Mg powder

2017; Volume: 19; Issue: 1 Linguagem: Inglês

10.9714/psac.2017.19.1.042

2287-6251

S.H. Kim, Wangu Kang, Y.J. Lee, Byung‐Hyuk Jun, C.J. Kim,

Boron and Carbon Nanomaterials Research

The effects of the heat treatment temperature ( $600^{\circ}C-1050^{\circ}C$ ) on the formation of $MgB_2$ and the superconducting properties have been examined. The self-synthesized $MgB_4$ and commercial Mg powders were used as raw materials for the formation of $MgB_2$ . The superconducting critical temperatures ( $T_cs$ ) of $MgB_2$ bulk superconductors prepared at $600^{\circ}C-850^{\circ}C$ were as high as 37-38 K regardless of the heat treatment temperature. However, because $MgB_4$ is more stable than $MgB_2$ at above $850^{\circ}C$ , no superconducting signals were detected in the susceptibility-temperature curves of the samples prepared above $850^{\circ}C$ . As for the critical current density ( $J_c$ ), the sample heat-treated at a low temperature ( $600^{\circ}C$ ) for a prolonged period (40 h) showed a Jc higher than those prepared at $650^{\circ}C-850^{\circ}C$ for a short period (1 h). The FWHM (full width at half maximum) result showed that the grain size of $MgB_2$ of the $600^{\circ}C$ sample was smaller than that of the other samples. The high $J_c$ of the $600^{\circ}C$ sample is attributed to the presence of large numbers of grain boundaries, which can act as flux pinning centers of $MgB_2$ .