Superconductivity in three-layer Na0.3CoO2·1.3H2O

The observation of superconductivity at 4.3 K in a new crystalline form of Na0.3CoO2·1.3H2O is reported. The new superconductor has three layers of CoO6 octahedral per crystallographic unit cell, in contrast to the previously reported two-layer superconductor. The three-layer cell occurs because the relative orientations of neighboring CoO2 layers are distinctly different from what is seen in the two-layer superconducting phase. This type of structural difference in materials that are otherwise chemically and structurally identical is not possible to attain on the layered copper oxide superconductors. The synthesis and stability of the new phase are described.