Effect of starting composition and annealing temperature on irreversibility field and critical current density in MgxB2

✍ Scribed by G.J. Xu; R. Pinholt; J. Bilde-Sørensen; J.-C. Grivel; A.B. Abrahamsen; N.H. Andersen

• Publisher: Elsevier Science
• Year: 2006
• Tongue: English
• Weight: 172 KB
• Volume: 434
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/j.physc.2005.12.002

✦ Synopsis

Bulk samples of Mg x B 2 with starting composition of 0.5 6 x 6 1.3 were prepared using a solid-state reaction route. Their structure and critical current density (J c ) were investigated. The experimental results show that the starting composition Mg x B 2 , as well as the sintering temperature, has a significant influence on J c and H irr . The lattice parameter a increases with x and c shows a maximum value around x = 0.9. All the samples possess a J c value about 10 6 A/cm 2 in self-field for x > 0.5. However, at high magnetic field the Mg-deficient samples exhibit higher J c values. The highest irreversibility field of H irr = 5.2 T at 20 K was reached for x = 0.8 with sintering temperature of 800 °C, which is 0.8 T higher than that of the stoichiometric MgB 2 sample. It is suggested that the formation of MgB 4 nanoparticles is responsible for the increase of H irr and J c .