Effects of Mn and Ti doping on superconductivity in Na0.3CoO2 · 1.3H2O and charge ordering in Na0.5CoO2

The superconductivity in Na0.3Co1−xMxO2 · 1.3H2O and the charge ordering in Na0.5Co1−xMxO2 have been investigated for M = Mn and Ti substitution for Co. Single-phased Na0.5Co1−xMxO2 (0 ⩽ x ⩽ 0.1, M = Mn, Ti) materials were prepared by Na deintercalation from Na0.75Co1−xMxO2; the hydrated Na0.3Co1−xMxO2 · 1.3H2O (0 ⩽ x ⩽ 0.1, M = Mn, Ti) materials were prepared by Na deintercalation and then water intercalation. Measurements of physical properties demonstrated that the superconductivity in Na0.3Co1−xMxO2 · 1.3H2O is evidently influenced by the Co-site doping and completely ceases at x = 0.02 for Mn doping and x = 0.01 for Ti doping. Analysis of resistivity and magnetization on Na0.5Co1−xMxO2 revealed that Mn doping has much stronger influence than Ti doping on both the charge ordering and the low-temperature physical properties.