| Layered cobalt oxides NaxCoO2 have been widely studied for their high thermoelectric power. The thermoelectric properties can be improved by the incorpration of dopants into the layer structured oxides. NaxCoO2 has attracted significant interest because of the novel 5K superconductivity in Na0.35CoO2·1.3 H2O.The crystal structure,the layer distance and superconductivity can be influenced by the incorpration of dopants into the layer structures.Nao.7CoO2 and Nao.7Co1-xFexO2(x=0.03,0.07,0.10) were synthesized by solid state reaction method. The XRD results showed that Fe could be partially substituted for Co in the Na0.7CoO2 lattice. The lattice parameters c increased with Fe doping. The electric property test showed that the electrical conductivity,σ, obviously decreased for the reason of Fe substitution. The Seebeck coefficient, a, increased with Fe doping, which can be attributed to the increase of the specific heat, Ce. The degree of the increase of Seebeck coefficient was less than that of the decrease of the electrical conductivity, so that, Fe doping led to a decrease in the power factor,α2σ.and Nao.7Co0.9M0.1O2(M= Fe,Ni,Cu) were synthesized by sol-gel method. Na0.7Co0.9M0.1O2 crystallized in a hexagonal crystal structure(P63/mmc) with an increasing lattice parameters c.Na0.3CoO2 and Na0.3Co0.9M0.1O2 were obtained by NaC1O4 saturated solution. The electric property test showed that the electrical conductivity,σ, obviously decreased for the reason of substitution. The Seebeck coefficient,α, increased with doping.The element doping led to a decrease in the power factor,α2σ. The presence of Fe,Ni and Cu had a detrimental effect on superconductivity and led to abnomal magnetic property.The organic-inorganic complex was synthesized by Nao.3CoO2 and CH3CH2NH2. The XRD results showed that the lattice parameters c was increased.The IR test showed the exist of C-H and N-H. No superconductivity was found in the complex. |
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