Transport and CuK-XANES studies of (Hg,Cr)Sr-2(Ca,Y)Cu2O6+delta

Abstract

The nominal (Hg0.7Cr0.3)Sr-2(Ca0.7Y0.3)Cu2O6+delta, referred to as (Hg,Cr)-1212, were successfully synthesized at high temperature in partial vacuum. The samples were subsequently annealed in Ar or O-2 annealed at 300degreesC under ambient pressure. No T-c was observed in any of these samples down to 12 K which is in contrast to high pressure synthesized Y-free (Hg,Cr)-1212 phase where the latter exhibits a superconductivity at similar to80K. The divalent state of Cu,as shown by XANES in the as-prepared (Hg,Cr)-1212, is not affected either by Ar or O-2 annealing. Depletion of holes due to trivalent Y substitution at the Ca-site, and a relatively higher 'a' lattice parameter ( greater than or equal to3.851 Angstrom) are the apparent reasons for the non-superconducting nature of the samples.