PRESSURE-INDUCED ENHANCEMENT OF T(C) ABOVE 150-K IN HG-1223

The recently discovered homologous series HgBa2Can-1CunO2n+2+delta pos sesses remarkable properties. A superconducting transition temperature , T(c), as high as 133 kelvin has been measured in a multiphase Hg-Ba- Ca-Cu-O sample and found to be attributable to the Hg-1223 compound. T emperature-dependent electrical resistivity measurements under pressur e on a (>95%) pure Hg-1223 phase are reported. These data show that T( c) increases steadily with pressure at a rate of about 1 kelvin per gi gapascal up to 15 gigapascals, then more slowly and reaches a T(c) = 1 50 kelvin, with the onset of the transition at 157 kelvin, for 23.5 gi gapascals. This large pressure variation (as compared to the small eff ects observed in similar compounds with the optimal T(c)) strongly sug gests that higher critical temperatures could be obtained at atmospher ic pressure.