1 Risø National Laboratory for Sustainable Energy, Technical University of Denmark2 unknown3 Department of Management Engineering, Technical University of Denmark4 Department of Energy Conversion and Storage, Technical University of Denmark5 Department of Wind Energy, Technical University of Denmark6 Department of Physics, Technical University of Denmark
Bulk samples of MgxB2 with starting composition of 0.5 <= x <= 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 MgxB2, 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 degrees C, which is 0.8 T higher than that of the stoichiometric MgB2 sample. It is suggested that the formation of MgB4 nanoparticles is responsible for the increase of H-irr and J(c). (c) 2005 Published by Elsevier B.V.
Physica C: Superconductivity and Its Applications, 2006, Vol 434, Issue 1, p. 67-70