HGSR2CUO4- A NEW 78 K SUPERCONDUCTOR BY MO SUBSTITUTION(DELTA )

A new series of strontium-based (Hg, Mo)-1201 superconducting compound s has been synthesized. The highest T-c of the series (78 K) is found for the nominal composition (Hg0.85Mo0.15)Sr2CuO4+delta with lattice c onstants: a = 3.787 Angstrom and c = 8.844 Angstrom. X-ray diffraction and SEM with EDX analysis confirm that Hg and Mo are indeed incorpora ted in the structure. High-pressure oxygenation at 250 bar and 325 deg rees C, and also at 1 bar, reduces the T-c indicating that the samples are overdoped. The a-axis increases and c-axis decreases with increas ing Mo concentration, suggesting that Mo substitutes in the Hg-O layer rather than in the CuO2 layer.