MgB2 bulk superconductors are synthesized by the solid state reaction of (MgB4+xMg) precursors withexcessive Mg compositions (x=1.0, 1.4, 2.0 and 2.4). The MgB4 precursors are synthesized using (Mg+B) powders. Thesecondary phases (MgB4 and MgO) present in the synthesized MgB4 are removed by HNO3 leaching. It is found thatthe formation reaction of MgB2 is accelerated when Mg excessive compositions are used. The magnetization curves ofMg1+xB2 samples show that the transition from the normal state to the superconducting state of the Mg excessive sam-ples with x=0.5 and x=0.7 are sharper than that of MgB2. The highest Jc-B curve at 5 K and 20 K is achieved forx=0.5. Further addition of Mg decreases the Jc owing to the formation of more pores in the MgB2 matrix and smallervolume fraction of MgB2.

1. 서 론
 2. 실험방법
 3. 결과 및 고찰
 4. 결 론
 Acknowledgement
 References

• 정현덕(한국기술교육대학교 신소재공학과, 한국원자력연구원 중성자응용기술부) | Hyeondeok Jeong
• 김찬중(한국원자력연구원 중성자응용기술부) | Chan-Joong Kim
• 전병혁(한국원자력연구원 중성자응용기술부) | Byung-Hyuk Jun
• 김설향(한국원자력연구원 중성자응용기술부, 성균관대학교 물리학과) | Seolhyang Kim
• 박해웅(한국기술교육대학교 신소재공학과) | Hai-Woong Park Corresponding Author