【摘要】：由于6s2孤對電子效應,含有Pb~(2+)和Bi~(3+)離子的化合物通常表現(xiàn)出來獨特的物理性質,例如鐵電性和非線性光學效應等,在材料學領域備受關注。本文圍繞含有Pb~(2+)和Bi~(3+)的化合物Pb3Mn7O15和Mn Bi2S4開展研究。本文根據(jù)這兩個化合物的結構特點,結合元素的化學性質,設計合成新固溶體;進而利用衍射技術(包括X射線粉末衍射、中子衍射),電子顯微技術(包括掃描電鏡等),結合其他一系列物理、化學性質測量,研究所得化合物的結構及相變特點;再測量其電學與磁學性質,并討論結構和性質的關系。主要研究結果如下:1.發(fā)現(xiàn)了以Mn O2和Pb O為原料合成Pb3Mn7O15的最佳條件:合成溫度為850℃,Pb O過量5 wt%。Pb3Mn7O15在室溫下為正交結構(Pnma),隨著溫度的上升,在t=142℃時,轉變?yōu)榱浇Y構(P63/mcm);當溫度升至300℃時,轉變?yōu)榱硗庖环N六方結構;這兩個相轉變過程是可逆的。隨著溫度的進一步上升至950~1 000℃,Pb3Mn7O15發(fā)生分解,分解產物為Mn3O4和Pb O。在750~800℃之間,Pb4Mn9O20可以轉化為Pb3Mn7O15,該轉變?yōu)椴豢赡孓D變2.發(fā)現(xiàn)了兩個新固溶體Pb3Nix Mn7-x O15-δ(0≤x≤0.6)和Pb3Cox Mn7-x O15-δ(0≤x≤0.5)。固溶體在不同的摻雜量具有出不同的晶體結構。Pb3Nix Mn7-x O15-δ在0≤x≤0.2時為正交相(Pnma),在0.2≤x≤0.6為六方相(P63/mcm)。Pb3Cox Mn7-x O15-δ在0≤x≤0.25時為正交相(Pnma),在0.25≤x≤0.5為六方相(P63/mcm)。Ni/Co摻雜元素在固溶體中均以正三價離子存在,而且傾向于優(yōu)先占據(jù)Kagome層內的Mn離子位點。Ni3+/Co3+摻雜擾亂層內Mn離子之間的磁相互作用,使其磁有序溫度降低或消失。固溶體均表現(xiàn)半導體導電性,隨著Ni、Co摻雜量的增加,化合物的電阻率下降。3.發(fā)現(xiàn)了一個新的固溶體Mn1 x CuxBi2S4(0.1≤x≤0.45)。其中Cu以+1價離子的形式存在,Mn以+2價離子的形態(tài)存在,Bi以+3價離子的形態(tài)存在。Cu+離子摻雜會向化合物中引入帶有正電荷的空位,其取代過程可用下式來描述:Mn~(2+)→Cu~+ + hole~+空位的存在導致Bi~(5+)和Mn~(3+)的形式上存在,同時導致化合物的晶胞體積隨摻雜量x的增加而增大。摻雜量的增加導致磁性離子Mn2+之間的相互作用被稀釋,導致其低溫反鐵磁有序狀態(tài)在摻雜量為0.2≤x≤0.4樣品消失。
[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，

本文編號：2304832