| La2NiO4+δ(B-site doped) is adopted as the cathodic material of SOFC, and analyse the doped possibility of Fe and Co in La2NiO4+δ. In this dissertation, La2Ni1-xFexO4+δ and La2Ni1-xCoxO4+δ series compounds were synthesized. The influence of composition and sintering conditions on the structure, nonstoichiometric oxygen and mixed conducting properties of the resulting products have been investigated.Using corrisponding nitrates as precursors, and ethylene diamine tetra acetic acid (EDTA) as precursors, La2Ni1-xFexO4+δ and La2Ni1-xCoxO4+δ powders were prepared by sol-gel method. Substituting partial Ni with Fe at the B-site caused an aberrance of the [BO6] octahedron, to the advantage of the oxidation reaction. Fe mainly exists in the high values states such as Fe3+, The Fe substitution increased the oxygen nonstoichiometry, and the ionic conductivity. The FT-IR spectrums also reveale that the induced Fe may strengthen the Ni-O bond asymmetric vibration, which facilitates the mobility of non-stoichiometric interstitial oxygen ion in the lattice. AC impedance spectroscopy measurements were used to study the ionic conductivity as well as the ionic conductivity dependence on the coefficient x at the low temperature. The ionic conductivity increase with the increase of temperature is in accordance with the conduction mechanism of small polarons.The influence of Co substitution at the B-site on the structure and mixed conducting properties was investigated. Substituting partial Ni with Co at the B-site caused an increase in the length of Ni/Co-O bond in ab plane and La-O2 bond along the c axis. The presence of Co3+ and Co4+ restrains the oxidization of Ni2+ to Ni3+ in La2Ni1-xCoxO4+δ ceramics, leading to a reduction of Ni3+ content. The Co substitution increased the oxygen nonstoichiometry, at higher temperature, the ionic conductivity increase with the increase of coefficient x was also in accordance with the conduction mechanism of small polarons.
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