Superconducting at 40 K MgB2 -samples were obtained by direct reaction from elements in molybdenum crucibles under argon pressure. Pressure allows to provide annealing at temperature up to 1400C, that resulting in rise of Tc and compactness of the ceramics, suggesting that there is a homogeneity range of composition for the compound.

Hyoung Joon Choi, David Roundy, Hong Sun, Marvin L. Cohen, & Steven G. Louie Department of Physics, University of California at Berkeley, Berkeley, CA 94720, USA. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. Magnesium diboride is remarkable not only for its unusually high transition temperature of 39K for a sp-bonded metal [1] and its reduced isot...

We present fabrication and optical time-resolved photoresponse characterization of MgB2 superconducting thin films. The films were prepared on crystalline and flexible plastic substrates by vacuum co-deposition of B and Mg precursors and high-temperature annealing in an Ar or vacuum atmosphere. The post-annealed films exhibited very smooth surfaces and amorphous structures with nanocrystal incl...