A New Superconducting Phase of Sodium Cobalt Oxide

A new superconducting sodium cobalt oxide (see Figure, left) has been synthesized through soft-chemical modification using α-NaCoO2 as a parent compound, in place of the γ-Na0.7CoO2 used to make the first cobalt oxide superconductor (see Figure, right). A three-layer periodicity of the CoO2 stacking sequence exists in the present material, in contrast to a two-layer one in the previous. The new oxide has a superconducting transition at 4.6 K.