La_2Ni_(1-x)Fe_xO_(4+δ)复合氧化物的合成及表征

Preparation and Characterization of La_2Ni_(1-x)Fe_xO_(4+δ)

以EDTA为配位体,采用溶胶-凝胶法合成了La2Ni1-xFexO4+δ系复合氧化物,XRD结果表明,所有样品都具有K2NiF4型结构。通过碘量法测定结果表明Ni/Fe的平均化合价和样品的非化学计量氧含量,均随x的增加而增大;当x=0.2时,非化学计量氧含量最高为0.2462。通过FT-IR发现Fe的引入导致Ni-O键的振动加强,这有利于间隙氧离子的活动。交流阻抗法测定样品的离子电导率随x的增加而逐渐增大,同一样品离子电导率在低温段随温度的升高而增大,表现出小极化子占主要的电导作用。

With nitrates and ethylene diamine tetra acetic acid （EDTA） as precursors, La2Ni1-xFexO4＋δ powder was prepared by sol-gel method. XRD results indicate that the complex oxides have K2 NiF4 structure. The iodometric titration was used to determine both the oxidation state of Ni/Fe ions and the oxygen nonstoichiometry in La2Ni1-xFexO4＋δ. It has been found that the both mentioned above will increase with the increase of coefficient x. The oxygen nonstoichiometry reached at 0.2462 when x = 0.2. Fr-IR spectrums revealed 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. The ionic conductivity increases with the increase of coefficient x. The changes of conductivity with temperature below 650℃ are in accordance with the conduction mechanism of small polarons.