SUPERCONDUCTIVITY, MICROSTRUCTURE AND PRESSURE EFFECT ON T(C) OF HG-BASED COMPOUNDS PREPARED UNDER HIGH-PRESSURE

High-temperature superconductors of the mercury-based system were synt hesized under high temperature and high pressure. The measurements of resistance and DC magnetic susceptibility for the samples prepared at 20-35 kbar and 850-degrees-C for 1-3.5 h show that the as-synthesized sample (1) prepared at 20 kbar, 850-degrees-C for 1.5 h was a multipha se of Hg-1212 and Hg-1223 phases and showed superconducting transition s of both 132 and 120 K. The sample (2) prepared at 30 kbar, 850-degre es-C for 3.5 h has Hg-1212 as the major phase with only a small amount of impurity phase. The intergrowth of Hg-1212/Hg-1223 was found in th e sample (1). The dependence of pressure on T(c) for the Hg-1212 and H g-1223 phases, measured under hydrostatic pressure, shows that dT(c)/d p is 0.17 and 0.23 K/kbar, respectively, in the pressure range below 1 0 kbar.