Crystal structure of DyBa2Cu4O8: A new 77 K bulk superconductor

Abstract
Single‐crystal x‐ray diffraction data from DyBa2Cu4O8 are used to confirm the structure of RBa2Cu4O8 (R=Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, and Tm), all of which have been synthesized in bulk and display substantial Meissner diamagnetism. The structure is orthorhombic, space group Ammm, with a=3.846 3(3), b=3.872 6(3), and c=27.237(2) Å. Copper‐oxygen layers parallel to (001) are dimpled as in the 1‐2‐3 structure. Unique copper‐oxygen strips parallel to (100) have copper in distorted square‐planar coordination. Magnitudes of oxygen anisotropic thermal vibrations are significantly less than in the 1‐2‐3 structure; thus the oxygen content of 1‐2‐4 is expected to be significantly more stable.