Transport and Cu K-XANES Studies of (Hg,Cr)Sr2(Ca,Y)Cu2O6 + δ

The nominal (Hg0.7Cr0.3)Sr2(Ca0.7Y0.3)Cu2O6 + δ, referred to as (Hg,Cr)-1212, were successfully synthesized at high temperature in partial vacuum. The samples were subsequently annealed in Ar or O2 annealed at 300°C under ambient pressure. No Tc 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 ∼80 K. The divalent state of Cu, as shown by XANES in the as-prepared (Hg,Cr)-1212, is not affected either by Ar or O2 annealing. Depletion of holes due to trivalent Y substitution at the Ca-site, and a relatively higher 'a' lattice parameter (≥3.851 A) are the apparent reasons for the non-superconducting nature of the samples.