CRYSTAL-STRUCTURES OF STAGE-N IODINE-INTERCALATED COMPOUNDS IBI2NSR2NCANCU2NOX

The crystal structure of stage-3 iodine-intercalated superconducting IBi6Sr6Ca3Cu6Ox has been determined by transmission electron microscopy to belong to the space group Pma2 with lattice parameters a = 5.4 angstrom, b = 5.4 angstrom and c = 49.4 angstrom. Iodine atoms intercalated between every three Bi-O bilayers expand the distance between the Bi-O layers by 3.6 angstrom and alter the atomic stacking across Bi-O layers from the staggered configuration characteristic of host superconducting Bi2Sr2CaCu2Ox to an aligned configuration characteristic of stage-1 iodine-intercalated superconducting IBi2Sr2CaCu2Ox. Higher-stage intercalation has also been observed as stacking faults which predominantly contain both stage-2 and stage-3 phases. The space groups and c-axis dimensions of the higher-stage phases have been deduced to be Pma2 with c = 3.6 + 15.3n angstrom when stage number n is odd, and Bbmb with c = 2 (3.6 + 15.3n) angstrom when n is even.