Synthesis and characterization of (Tl_0.5Pb_0.5)Sr_3−xNd_xCu₂O₇ (0.5≤× ≤0.9)

Abstract

Rare earth substituted thallium cuprates of the type Tl_0.5Pb_0.5Sr_3−xNd_xCu₂O₇ have been synthesized having 1212 structure. A single phase region exists for x = 0.5 to 0.9. X-ray diffraction data suggest that the rare earth substitution occurs mainly at the Sr site rather than at the Tl site. No Superconductivity is observed for all the compounds down to 4.2 K. The compounds are semiconducting and this suggests that the Tl 6s/Pb 6s bands do not overlap with Cu 3d bands at the Fermi level in agreement with band structure calculations for one Tl---O layer cuprates.