The fourth member of the tubular family [Bi2Sr2CoO6](n)[Sr8Co6O16-delta]: Bi5.8Sr15.2Co10O40-delta

A new cobaltite, Bi5.8Sr15.2Co10O40-delta, with a tubular structure derived from the 2201-type has been synthesized. This oxide represents the n = 4 m ember of the large structural [Bi2Sr2MO6](n)[Sr8M6O16+/-delta] family (M = Cu, Mn, Co). Its average structure, similar to that of the copper-based pha se, crystallizes in the space group Fmmm with cell parameters a 5.4650(5) A ngstrom, b = 34.042(2) Angstrom, and c = 23.574(1) Angstrom. Its complex cr ystal chemistry has been studied using XRPD and HREM techniques. This struc ture can be described as an intergrowth along b, of two types of (010) slic es: "2201"-type slices [Bi2Sr2CoO6] that are four octahedron thick and coba lt-deficient perovskite-related slices [Sr8Co6O16-delta] that are one octah edra thick. The study of the magneto-transport properties of this new cobal tite shows an antiferromagnetic behavior below 80 K and a large decrease by 500 of the resistivity at room temperature by annealing under oxygen press ure.