抄録
We prepared single-phase Nax(H3O)zCoO2·y'H2O with varying amount of Br2 volume in acetonitrile, and examined the Na+ content (x), H3O+ content (z), H2O content (y') and Tc. By changing the amount of Br2 during preparation, the amount of x in Nax(H3O)zCoO2·y'H2O was controlled from 0.282 to 0.359. It was found that superconductivity is not correlated with Co valence but with y'/x, that is, the coordination number of Na+ with H2O, and secondly with x⁄x+z, that is, the ratio of Na+ ion in the (Na+ + H3O+) site, suggesting that shielding effect of Nax(H3O)zCoO2·y'H2O governs superconductivity.
