SUPERCONDUCTIVITY OF A NEW SERIES OF MERCURY-BASED CUPRATES (HG, M) SR-2 (ND, CA) CU2OZ (M=NB, TA)

A new series of mercury-based superconducting layered cuprates Hg0.75N b0.25Sr2(Nd1-xCax)Cu2O2 (0 less than or equal to x less than or equal to 0.4) has been synthesized. X-ray diffraction indicated that the com pounds exhibit the 1212 structure with a space group of P4/mmm. The in vestigation of superconductivity determined by an electrical-resistanc e measurement shows that the samples are superconducting; a T-c (onset ) of 80 K is found in the sample Hg0.75Nb0.25Sr2Nd0.6Ca0.4Cu2O2. By su bstitution of Ta for Nb, the isostructural cuprates can be synthesized with a similar superconducting behavior.