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采用溶胶-凝胶(sol-gel)法制备La0.6A0.4MnO3(A代表Cu,Ag,Na)多晶样品材料,用X射线衍射(XRD)以及X射线光电子能谱(XPS)对其进行了研究,发现La0.6Cu0.4MnO3,La0.6Na0.4MnO3均为单相菱面体钙钛矿结构,而La0.6Ag0.4MnO3则由菱面体结构的钙钛矿相和立方结构的金属Ag相组成。对LaMnO3母体进行A位掺杂,随着离子半径不同的金属阳离子的掺入,会导致样品产生晶格畸变,从而使样品的晶格常数,晶胞体积发生变化,变化趋势与掺入的金属阳离子半径有关。随着掺杂离子半径的增大,样品晶格常数、晶胞体积也相应增大。La在La0.6A0.4MnO3(A代表Cu,Ag,Na)中均以正三价形式存在,表明La在化合物中是起稳定作用的组分。随着低价态的金属阳离子(Cu2+,Ag+,Na+)替代La3+,将有更多的Mn3+通过Mn-O-Mn的双交换作用变为Mn4+,从而满足试样整体电荷守恒。
La0.6A0.4MnO3 (Cu, Ag, Na) polycrystalline samples were prepared by sol-gel method and characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy The study found that La0.6Cu0.4MnO3, La0.6Na0.4MnO3 are single-phase rhombohedral perovskite structure, and La0.6Ag0.4MnO3 by the rhombohedral structure of the perovskite phase and the cubic structure of the metal Ag phase composition . A-site doping of LaMnO3 matrix, with the addition of metal ions with different ionic radius, will lead to sample lattice distortion, so that the lattice constant of the sample, the unit cell volume changes, the trend of change with the incorporation of metal Cation radius related. With the increase of doping ion radius, the lattice constant and the unit cell volume of the sample increase accordingly. La exists in the ortho-trivalent form in La0.6A0.4MnO3 (A represents Cu, Ag, Na), indicating that La is a stable component in the compound. With the replacement of La3 + with lower valence metal cations (Cu2 +, Ag +, Na +), more Mn3 + will be converted into Mn4 + by double exchange of Mn-O-Mn to satisfy the overall charge conservation of the sample.