【作者】 杨美琦；

【导师】 冯守华；

【作者基本信息】 吉林大学 ， 无机化学， 2010， 硕士

【摘要】 本论文主要研究在水热体系下A,B位共掺杂的钙钛矿型锰基氧化物的合成方法。对锰酸镧母体化合物进行A位Ca离子和B位Fe离子共掺杂系列化合物的水热合成反应条件进行了系统的探索,确认了产物的结构组成。首次在水热条件下合成了B位Fe掺杂双钙钛矿型稀土锰氧化物,对合成方法及反应条件进行了详细的说明。在第一章绪论中,我们介绍了关于钙钛矿结构的锰基复合氧化物的相关基础知识及基本理论,对掺杂钙钛矿及双钙钛矿的研究现状进行了总结;在第二章实验部分,我们介绍了在水热条件下合成La-Ca-Mn-Fe-O系列化合物的反应条件,实现了对A位和B位离子的可控性调变,并初步讨论了由于掺杂而引起的结构,磁电性质等方面的变化情况;在第三章实验中,我们首次利用水热方法得到了双钙钛矿化合物Ln2FeMnO6(Ln=Gd, Tb, Dy, Ho)系列样品,并对其组成,结构与晶体形貌进行说明。更多还原

【Abstract】 The traditional method of the synthesis of perovskite manganese oxide compounds is high-temperature solid-phase method, although the operation method is simple, easy to master, but the shortcoming of this method is also very typical,for example, the high cost of high-temperature sintering, with intermediate repeatedly grinding, and there are always many vise production as multi-phase or mixed phase. It causes disadvantage for further chemical and physical tests.In this thesis, we mainly discuss the synthetic method and reaction conditions of A, B site doped perovskite type manganese oxide compounds by hydrothermal system, focus on the composition and structure of the product, and part of the series magnetic compounds were characterized. The purpose of this study is to get to the information of the synthesis of ions doped manganite in both A and B site, and achieve the controllability of the composition modulation.1. A Series of compounds with the formula La-Ca-K-Fe-Mn-O has been synthesized under mild hydrothermal conditions, respectively, A site of Ca ions and B-site of Fe ion doping was carried out in detail the composition of the modulation, including the two Part: a)Ca_xLa_yK_1-x-yMnFeO₆（0.1=<x<0.5） Series samples with the changes quantum of Ca²⁺ doped in A site and a detailed study of the compound of preparation conditions, analysis of the product structure, structure and doping effect on the impact of B-bit architecture; b) La_0.5Ca_0.5Mn_1-xFe_xO₃（0.1=<X<0.5） Series samples with the changes quantum of Fe³⁺ doped in B site, introductions of the best synthesis conditions, the product structure was analyzed and gave rise to an analysis of the magnetic changes.Compared with conventional solid-phase synthesis methods, hydrothermal synthesis has a low reaction temperature, the high quality product, uniformed size distribution, regular crystal morphology, etc.. Studies have shown that hydrothermal reaction system conditions require accurate conditions, reactant ratios, crystallization temperature, the alkalinity of reaction system and other conditions were limited to very small changes in range. As the composition of the system complexity, we have adopted a variety of test methods for their valence state, structure and composition. A more detailed analysis and find that the increase in the amount of Ca ion doping on A-site results few changes of the bond length or bond angle of BO₆ octahedron. With the Fe³⁺ doping in B site, changes happen in BO₆ octahedron and with the increasing of Fe³⁺, ferromagnetic of the system weakened while anti-ferromagnetic phase significantly increases.2. A series of double perovskite of B-site Fe, Mn-doped compounds Ln2MnFeO₆ （Ln = Gd, Tb, Dy and Ho） have been synthesized by hydrothermal mothed for the first time. Optimise reaction conditions were reported in this study. The structure and component of this new compound was detected by many instruments. X-ray powder diffraction was used to confirmed its structure by an initial, ICP combination EDS spectra to confirm its composition, further observation of morphology was shown by SEM, the series of work illustrate that the compounds were of high purity, clear crystal structure, and show the advantages of hydrothermal synthesis method one more time. Because few reports about the compound, to make clear the focus on the next stage of the study, we did DSC thermal analysis, found that there is a phase transition about 300℃regularly, whereby we put forward the next stage of the study direction.更多还原