层状化合物La_2Ni_(1-y)Co_yO_(4+δ)的合成、结构与性能

Preparation, Structure and Properties of La_2Ni_(1-y)Co_yO_(4+δ) Layered Compounds

采用氨基多羧酸配合物法合成La2Ni1-yCoyO4＋δ（y=0～0.2）超细粉料，研究陶瓷样品的结构和混合导电性能.研究结果表明，La2Ni1-yCoyO4＋δ具有正交结构（Fmmm空间群），Co离子取代增加了钙钛矿层中ab平面上Ni/Co—O键的键长、岩盐层中沿c轴方向上La—O键的键长和非化学计量氧含量，并有利于改善材料的烧结性能.随着Co离子含量的增加，总电导率的峰值温度向高温移动，高温段总电导率随温度的变化趋于平缓，但总电导率水平出现降低；增加Co离子含量还有利于提高氧离子导电性能.Co离子取代对陶瓷样品混合导电性能的影响与晶体结构参数的变化紧密相关.

La2Ni1-yCoyO4＋δ（y =0-0. 2） fine powders were synthesized by a polyaminocarboxylate complex method, and the structure and mixed conducting properties of the resulting ceramics were investigated. X-ray diffraction Rietveld refinement results indicate that La2Ni1-yCoyO4 ＋δ compositions have an orthorhombic structure with Fmmm space group. The substitution of partial La3＋ with Co at the B-site caused an increase in the length of Ni/Co-O1 bond in the ab plane and La/Sr-O2 bond along c axis. Moreover, it was detected that the oxygen nonstoichiometry（6） became larger with increasing Co content. The cobalt substitution resulted in a shift of the temperature for the electrical conductivity maximum to higher temperature direction and a decline of electrical conductivity together with a modification of oxygen ionic conducting properties. The effect of cobalt substitution on the mixed conducting properties of La2NiO4＋δ ceramic can be interpreted with respect to the variation in crystal structure parameters.