首页> 外文会议>Structure-Property Relationships of Oxide Surfaces and Interfaces II >EFFECT OF LANTHANUM MANGANITE MODIFICATION BY CALCIUM AND/OR FLUORINE ON THE BONDING STRENGTH, MOBILITY AND REACTIVITY OF THE LATTICE AND SURFACE OXYGEN
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EFFECT OF LANTHANUM MANGANITE MODIFICATION BY CALCIUM AND/OR FLUORINE ON THE BONDING STRENGTH, MOBILITY AND REACTIVITY OF THE LATTICE AND SURFACE OXYGEN

机译:钙和/或氟改性镧锰对晶格和表面氧结合强度,流动性和反应性的影响

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Ca and/or F-modified samples of LaMnO_3 have been prepared by the Pechini method. The bulk structure of samples was characterized by TEM, EXAFS and XRD, while the surface composition was studied by SIMS. Thermal analysis, O_2 TPD, H_2 TPR and isothermal pulse/flow samples reduction by CO were applied to characterize the accessible surface/bulk oxygen mobility and reactivity. A reasonable description of the experimental energetic spectrum of the surface oxygen for various types of regular and defect surface sites on the perovskite faces was achieved by using semiempirical Interacting Bonds Method in the slab approximation with a due regard for the surface face termination and relaxation. Fluorine was found to decrease the surface coverage by reactive weakly bound oxygen forms while increasing the bulk oxygen excess and mobility. Calcium generated reactive weakly bound oxygen forms while decreasing the oxygen excess in the lattice and converting the regular M-O oxygen forms into the bridging ones through migration to the surface.
机译:已通过Pechini方法制备了LaMnO_3的Ca和/或F改性样品。用TEM,EXAFS和XRD对样品的整体结构进行了表征,而用SIMS研究了其表面组成。应用热分析,O_2 TPD,H_2 TPR和通过CO降低等温脉冲/流量样品来表征可及的表面/大量氧的迁移率和反应性。通过在平板近似中使用半经验相互作用键方法,并适当考虑了表面端面的终止和松弛,对钙钛矿表面上各种类型的规则和缺陷表面部位的表面氧的实验高能谱进行了合理的描述。发现氟通过反应性弱结合的氧形式减少表面覆盖,同时增加大量的氧过量和迁移率。钙生成的反应性弱结合氧形式,同时减少了晶格中过量的氧,并通过迁移到表面将规则的M-O氧形式转变为桥联形式。

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