A comparison of the structural evolution induced by changing the hole-doping level in three series (Hg, Tl)-22(n - 1)n (n = 2, 3) samples

Three series of (Hg, Tl)-22(n - 1)n (n = 2, 3) samples were synthesized by a high-pressure technique. One series of samples was prepared by substituting Y for the Ca site in (Hg_0.7, Tl_0.3)₂Ba₂(Y_x, Ca_1-x)Cu₂O_8-2δ (x = 0.4, 0.6, 0.8 and 0.9), while two other series were prepared by annealing (Hg_0.7, Tl_0.3)₂Ba₂(Y_0.8, Ca_0.2)Cu₂O_8-2δ and (Hg_0.6, Tl_0.4)₂Ba₂Ca₂Cu₃O _10-2δ samples in Ar. The crystal structures of the samples were determined by x-ray Rietveld refinement. The variation tendencies of their lattice parameters as well as several particular inter-planar distances with the change of the hole doping level in these three series were investigated and compared with one another. Based on the comparison, a qualitative explanation for the structural evolution tendency under hole doping for these series was proposed.