Microwave properties of superconducting MgB2

Measurements of 10 GHz microwave surface resistance, R-s, of dense MgB2 wir e and pellet are reported. Significant improvements are observed in the wir e with reduction of porosity. The data lie substantially above the theoreti cal estimates for a pure Bardeen-Cooper-Schrieffer s-wave superconductor. H owever, the R-s (20 K) of the wire is an order of magnitude lower than that of polycrystal YBa2Cu3O6.95 and matches with single-crystal YBa2Cu3O6.95. The results show promise for the use of MgB2 in microwave applications. (C) 2001 American Institute of Physics.