Abstract
All the high- T c oxide superconducors known to date are copper-based oxides (cuprates) in the layered perovskite crystal structures that contain a planar network of copper and oxygen (CuO 2 plane). In searching for possible new superconducting metal oxides without Cu ions, we have examined the layered tetragonal pnictides M 4Pn 2O (M=Ca, Sr, Ba and Pn=As, Sb, Bi) because their structures are considered as an anti-perovskite with alternate stacking of two kinds of layers; conducting M 2Pn 2 block layers sandwiched by insulating perovskite-based M 2O layers. Compounds were prepared by melting stoichiometric amounts of the components in tantalum tube all sealed under an argon atmosphere. The samples have been characterised by scanning electron microscopy, powder X-ray diffraction (XRD), metallographic examination and electrical resistivity. For these stoichiometric compounds no superconductive transition is observed.
Published Version
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