Superconducting properties of Hg-1223 prepared by using fluorides

A new approach involving the use of fluorides has been adopted to synthesize phase-pure Pb-substituted Hg-1223 superconductors under ambient conditions. A representative sample is characterized using x-ray, SQUID magnetometer, and ac susceptibility techniques. In a measuring field of 1 G, a sharp diamagnetic onset is observed at 132 K and perfect flux screening persists up to 122 K. On approaching T_c the irreversibility llle follows a power law with exponent α=2.2. From the ac susceptibility data, in the context of the Bean critical state model, the critical current density at helium temperatures is estimated to be 1.5×10⁶ A/cm².