Hg0.95Re0.05Ba2Ca2Cu3O8+delta superconductor: sample preparation and transport properties under hydrostatic pressure

Samples of the Hg1-xRexBa2Ca2Cu3O8+delta superconductor (Hg, Re-1223), with low rhenium (Re) content (x = 0.05), have been produced with the help of a novel thermobaric analysis technique which could monitor the total pressur e inside the quartz tube during synthesis at high temperature. The sample q uality was verified by means of Rietveld analysis of the x-ray diffraction data. and by ac susceptibility measurements. The formation and stability of the Hg, Re-1223 phase has also been investigated by varying the oxygen con tent of the Re0.05Ba2Ca2Cu3O8+delta precursor, and the mercury filling fact or (ff(Hg) = 0.00 to 0.014 g cm(-3)). It was observed that the reduction of oxygen content in the precursor (Re0.05Ba2Ca2Cu3O8+delta) and the increase of the mercury partial pressure inside the quartz tube enhanced the yield of the superconductor phase. Resistance measurements as a function of temperature under hydrostatic pres sure (0-1.0 GPa) show an increase in the superconducting transition tempera ture which can be fitted with a parabolic curve. The reduction of the latti ce volume induced by external hydrostatic pressure is similar to the one in duced by chemical pressure due to rhenium (Re) doping (0.00 < x < 0.10); ho wever Te does not depend on the chemical pressure. This behaviour can be un derstood on the basis of the pressure-induced charge transfer model (PICTM) modified by Almasan et al.