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

Abstract: The superconductivity in Na0.3Co1−x M x O2 ·1.3H2O and the charge ordering in Na0.5Co1−x M x O2 have been investigated for M=Mn and Ti substitution for Co. Single-phased Na0.5Co1−x M x O2 (0⩽ x ⩽0.1, M=Mn, Ti) materials were prepared by Na deintercalation from Na0.75Co1−x M x O2; the hydrated Na0.3Co1−x M x O2 ·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−x M x O2 ·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−x M x O2 revealed that Mn doping has much stronger influence than Ti doping on both the charge ordering and the low-temperature physical properties. [Copyright &y& Elsevier]