Explore Investigation On The Preparation Of High Dense MgB₂ Superconductor

The discovery of superconductivity in the simple MgB₂ crystalline intermetallic compound has aroused the extensive interests of world scientists to investigate the structure of MgB₂, the mechanism of superconduction, the synthesis methods and prospects for its commercial use. In this paper, aiming at the poor tightness of MgB₂ bulks with sintering method, which would affect superconductivity, it was clarified the forming process of MgB₂ phase and the effects on the tightness of MgB₂ bulks from three important technical parameters: sintering temperature, doping elements and sintering pressure, then the better sintering techniques benefiting for forming high density MgB₂ bulks were acquired. XRD, DSC, and SEM were adopted to analyze the MgB₂ bulks sintered at different temperature: 650℃, 700℃, 750℃and 850℃, the alloy of Mg1-xZrxB₂ (x=0.05, 0.1 and 0.2) and the alloy of Mg0.8Zr0.2B₂ sintered at different pressure: vacuum and 1.15atm. The result showed that the tightness of MgB₂ bulks sintered at 750℃is good, the same as Mg1-xZrxB₂ alloy sintered with x=0.1 and Mg0.8Zr0.2B₂ alloy sintered at 1.15atm.Just because of getting no high dense MgB₂ bulks with conventional sintering methods, scientists are finding a simple technique to fabricate MgB₂ bulks. So the method of high frequency melting was tried preparing MgB₂ bulks in the paper. But the primary problem in the method was the choice of suitable alloys which decided whether MgB₂ phase came into being or not. By analysis, two groups of alloys were chose, Mg1-xZrxB₂ (x=0.05, 0.1and 0.2) and Mg-Ag-Cu-B. XRD, DSC, OM and SEM were also adopted to analyze the alloys. With the increase of proportion of Zr, though the ability of grains connecting could be improved in the alloy of Mg1-xZrxB₂, MgB₂ phase formed as the secondary phase. However, MgB₂ phase formed as the primary phase in the alloy of Mg-Ag-Cu-B, so the alloy could be an ideal composition of alloy for preparing superconductor of MgB₂ bulks with the method of high frequency inductive melting.