Transport study of Hg-based high temperature superconductors

Polycrystalline superconductors Hg/sub 1/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub 8+/spl delta// were synthesized from oxides by the solid state reaction. Thermoelectric power, thermal conductivity and electrical resistivity of the Hg-based high temperature superconductors were measured in a broad temperature range between 20 and 300 K. The influence of magnetic fields up to 0.35 T was also studied. The superconducting transition starts at about 136 K and is completed in a relatively narrow temperature interval as revealed by thermoelectric power and resistivity measurements. The transition interval broadens in a magnetic field. The experimental data are used to determine and discuss the figure of merit for the Hg1223 superconductor. The figure of merit increases in an external small magnetic field.