含铅、铋的过渡金属化合物的结构与磁电性质研究
发布时间：2018-11-01 19:07
【摘要】：由于6s2孤对电子效应,含有Pb~(2+)和Bi~(3+)离子的化合物通常表现出来独特的物理性质,例如铁电性和非线性光学效应等,在材料学领域备受关注。本文围绕含有Pb~(2+)和Bi~(3+)的化合物Pb3Mn7O15和Mn Bi2S4开展研究。本文根据这两个化合物的结构特点,结合元素的化学性质,设计合成新固溶体;进而利用衍射技术(包括X射线粉末衍射、中子衍射),电子显微技术(包括扫描电镜等),结合其他一系列物理、化学性质测量,研究所得化合物的结构及相变特点;再测量其电学与磁学性质,并讨论结构和性质的关系。主要研究结果如下:1.发现了以Mn O2和Pb O为原料合成Pb3Mn7O15的最佳条件:合成温度为850℃,Pb O过量5 wt%。Pb3Mn7O15在室温下为正交结构(Pnma),随着温度的上升,在t=142℃时,转变为六方结构(P63/mcm);当温度升至300℃时,转变为另外一种六方结构;这两个相转变过程是可逆的。随着温度的进一步上升至950~1 000℃,Pb3Mn7O15发生分解,分解产物为Mn3O4和Pb O。在750~800℃之间,Pb4Mn9O20可以转化为Pb3Mn7O15,该转变为不可逆转变2.发现了两个新固溶体Pb3Nix Mn7-x O15-δ(0≤x≤0.6)和Pb3Cox Mn7-x O15-δ(0≤x≤0.5)。固溶体在不同的掺杂量具有出不同的晶体结构。Pb3Nix Mn7-x O15-δ在0≤x≤0.2时为正交相(Pnma),在0.2≤x≤0.6为六方相(P63/mcm)。Pb3Cox Mn7-x O15-δ在0≤x≤0.25时为正交相(Pnma),在0.25≤x≤0.5为六方相(P63/mcm)。Ni/Co掺杂元素在固溶体中均以正三价离子存在,而且倾向于优先占据Kagome层内的Mn离子位点。Ni3+/Co3+掺杂扰乱层内Mn离子之间的磁相互作用,使其磁有序温度降低或消失。固溶体均表现半导体导电性,随着Ni、Co掺杂量的增加,化合物的电阻率下降。3.发现了一个新的固溶体Mn1 x CuxBi2S4(0.1≤x≤0.45)。其中Cu以+1价离子的形式存在,Mn以+2价离子的形态存在,Bi以+3价离子的形态存在。Cu+离子掺杂会向化合物中引入带有正电荷的空位,其取代过程可用下式来描述:Mn~(2+)→Cu~+ + hole~+空位的存在导致Bi~(5+)和Mn~(3+)的形式上存在,同时导致化合物的晶胞体积随掺杂量x的增加而增大。掺杂量的增加导致磁性离子Mn2+之间的相互作用被稀释,导致其低温反铁磁有序状态在掺杂量为0.2≤x≤0.4样品消失。
[Abstract]:The compounds containing Pb~ (2) and Bi~ (3) ions usually exhibit unique physical properties, such as ferroelectric properties and nonlinear optical effects, due to the solitary pair electron effect of 6s2, which has attracted much attention in the field of materials science. In this paper, Pb3Mn7O15 and Mn Bi2S4 compounds containing Pb~ (2) and Bi~ (3) were studied. According to the structural characteristics of the two compounds and the chemical properties of the elements, a new solid solution was designed and synthesized. Furthermore, the structure and phase transition characteristics of the compounds were studied by means of diffraction (including X-ray powder diffraction, neutron diffraction), electron microscopy (including scanning electron microscopy, etc.) and a series of other physical and chemical measurements. The electrical and magnetic properties are measured and the relationship between the structure and the properties is discussed. The main results are as follows: 1. The optimum conditions for the synthesis of Pb3Mn7O15 using Mn O 2 and Pb O as raw materials were found: the synthesis temperature was 850 鈩，
本文编号：2304832
[Abstract]:The compounds containing Pb~ (2) and Bi~ (3) ions usually exhibit unique physical properties, such as ferroelectric properties and nonlinear optical effects, due to the solitary pair electron effect of 6s2, which has attracted much attention in the field of materials science. In this paper, Pb3Mn7O15 and Mn Bi2S4 compounds containing Pb~ (2) and Bi~ (3) were studied. According to the structural characteristics of the two compounds and the chemical properties of the elements, a new solid solution was designed and synthesized. Furthermore, the structure and phase transition characteristics of the compounds were studied by means of diffraction (including X-ray powder diffraction, neutron diffraction), electron microscopy (including scanning electron microscopy, etc.) and a series of other physical and chemical measurements. The electrical and magnetic properties are measured and the relationship between the structure and the properties is discussed. The main results are as follows: 1. The optimum conditions for the synthesis of Pb3Mn7O15 using Mn O 2 and Pb O as raw materials were found: the synthesis temperature was 850 鈩，
本文编号：2304832
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