Low temperature synthesis of MgB2

We report the synthesis of MgB2 with bulk superconducting properties by conventional solid state methods at temperatures as low as 550 degreesC. Mg deficiencies of the type Mg1-xB2 were tested. T-c was found to decrease by about 1 K at large x, though the amount of nonstoichiometry, if any, is likely to be very small. For specific processing conditions, indications of the 25-30 K transition often seen in thin films were seen in the bulk materials. The lower temperature transition may be associated with the grain boundaries. These results indicate that it should be possible to fabricate MgB2 with bulk properties in in situ thin films at temperatures of 600 degreesC or less. (C) 2002 American Institute of Physics.