Influences of heat treatment and doping on microstructure and superconducting properties of MgB2 superconductor

The microstructure and superconducting properties of pure, Ti and Zr doped MgB2, which synthesized by solid reaction method. The heat treatment temperature are varied from 650 to 800 degrees C at ambient pressure. It is found that heat treatment temperature have obvious effect on grain size and MgB2 grains are greatly refined at 750 degrees C. Besides, Zr does not occupy the atomic site in the MgB2 crystal structure, but forms ZrB2 particles in the MgB2 matrix. The results of superconducting properties show that Mg0.9Zr0.1B2 have the highest J(c) value sintered at 800 degrees C. It is argued that the microstructure features with good grain connectivity of the Zr doped MgB2 fabricated at optimize heat treatment temperature may take the responsibility for the enhancement of J(c) in Zr-doped MgB2 bulk superconductor. The results show a good potential to fabricate high performance MgB2 bulks and wires at ambient pressure on an industrial scale. (c) 2006 Elsevier B.V. All rights reserved.