ENCAPSULATION METHOD FOR THE SYNTHESIS OF NEARLY SINGLE-PHASE SUPERCONDUCTING HGBA2CA2CU3O8+DELTA WITH T(C)GREATER-THAN-OR-EQUAL-TO-135-K

Nearly single-phase polycrystalline samples of HgBa2Ca2Cu3O8+delta were successfully synthesized under relatively simple and unprecedented synthesis conditions, i.e. at a ''low'' temperature ( < 700-degrees-C) and for a ''long'' period of time (5-168 h), using mono-oxide powders of Hg, Ba, Ca, and Cu as starting materials. A pressed powder mixture was heated t 665-degrees-C for approximately 75 h in an evacuated fused quartz tube, and then post-annealed in flowing O2 gas to exhibit a Meissner signal below 135.4 K. Zero resistance of this sample was observed at 133.9 K.