One-dimensional ceramic oxide superconductors

摘要

This application describes ceramic oxide superconductors, their precursors and methods of preparation. The superconductors contain no copper, but comprise the transition metals Nickel or Cobalt (M^T) together with bulky cations of Groups 2 and 1 of the Periodic Table (M²⁺ and M¹⁺) such as Ba²⁺ and K¹⁺. Their hexagonal crystal structure comprises parallel chains of highly covalent, octahedrally coordinated oxygen around the transition metal, which exhibits its highest valence +4. The octahedra are facet-linked forming polyacid chains or macroanions that run the full length of crystallites or single crystals along the c axis. The chains are separated by distances that prevent covalency or orbital overlap among them. They are held together by coulombic forces from the cations located between them that also run parallel to the c axis. Electrical current, carried by holes, can only flow within the chains. Thus the materials are one-dimensional superconductors of composition M²⁺_(1-x)M¹⁺_xM^TO_3-delta.