New shear-like structure: The 2212-related cuprate Bi₁₆Sr₂₈Cu₁₇O_69+δ

The strategy of shearing mechanism has been applied to the 2212 bismuth cuprate Bi₂Sr₂CaCu₂O₈. A new compound has been synthesized, Bi₁₆Sr₂₈Cu₁₇O_69+δ; it crystallizes in a monoclinic cell with a = 48.40 (1) Å, b = 5.495 (1) Å, c = 16.283 (4) Å, and β = 109.96 (2)°. This phase exhibits 2212 ribbons running along c that are 9 Bi atoms wide, and shifted by 5.3 Å with respect to each other; these ribbons are interconnected through thin layers involving CuO₆ octahedra. In spite of its close relations with an ideal (101)-shear “2212” structure, this cuprate cannot be considered as such and is termed (101)-collapsed “2212” cuprate in agreement with previous works on (010)-collapsed “2201” cuprates. The rupture of the [CuO₂]_∞ layers and the possibility of using these phenomena for creating columnar defects in high-T_c superconducting cuprates are also discussed.