Synthesis and characterization of (Hg, Bi)-based 1212-type cuprate superconductor (Hg0.67Bi0.33)Sr2(Y0.67Ca0.33)Cu2O6+δ (δ=0.68)

Abstract (Hg, Bi)-based 1212-type compound (Hg 0.67 Bi 0.33 )Sr 2 (Y 0.67(1) Ca 0.33(1) Cu 2 O 6+δ was synthesized by using the sealed quartz tube method. The T c(onset) based on resistance and AC susceptibility measurements was up to 100 K. Rietveld refinements of the structure of (Hg, Bi)-1212 were carried out in the tetragonal symmetry with space group P4/mmm. The lattice parameters are a =3.80960(8) A and c =12.0157(4) A. The refined Y:Ca ratio is 0.67(1):0.33(1) while the refined occupancy factor of the oxygen atoms located in the (Hg, Bi)-layer is 0.68(2). The results in the present experiment are explained based on the concept of mixed Cu valencies.