复合多铁性CoFe2O4-BaTiO3材料的制备和电磁性能研究.pdf

华中科技大学硕士学位论文 I 摘要复合多铁性材料由具有磁致伸缩效应的铁磁材料和具有压电效应的铁电材料复合而成,通过磁滞伸缩效应和压电效应之间的应力耦合作用,使得整个材料出现磁电耦合现象,即外加电场能导致材料磁化,反之,外加磁场能使材料极化。多铁性材料是近些年来凝聚态和材料学研究比较热门的一个方向。本文主要内容是对 CoFe 2 O 4-BaTiO 3复合陶瓷的制备工艺、结构、铁磁、铁电以及介电等性质进行研究。(1) 本文采用共沉淀法和硬酯酸溶胶凝胶两步湿化学方法制备了类核壳结构的 CoFe 2 O 4-BaTiO 3 复合陶瓷粉体。红外 FTIR 图谱表征结果表明我们已经成功地对 CoFe2O4 纳米颗粒用油酸进行了化学包覆,制备了能分散于正辛烷的磁流体,磁流体且能良好地分散于硬酯酸。通过 XRD 分析发现制备的复合粉体中只含 CoFe 2 O 4 和 BaTiO 3 这两个相,没有其他杂相,说明成功制备了 CoFe 2 O 4-BaTiO 3 复合陶瓷粉体。(2) 本文将 CoFe 2 O 4-BaTiO 3复合粉体制备成陶瓷块材,通过改变组份、烧结温度、保温时间、压片压力四个陶瓷制备工艺参数, 制备了不同系列的复合多铁性材料样品。通过对不同系列样品的铁电、介电、铁磁性能的研究,最终获得制备多铁陶瓷的最佳工艺参数。研究发现,样品 CoFe 2 O 4/BaTiO 3 (1 : 4),20Mpa 压力下压片, 1150 ℃保温 4h 时制备的陶瓷样品的铁电铁磁性最好。(3 本文对固相原位反应(In situ) 、冰乙酸溶胶凝胶复合方法(AAG) 、硬脂酸溶胶凝胶复合方法(SAG) 三种不同方法制备的陶瓷进行了铁电、介电、铁磁性能的分析, 发现 SAG 方法在提高其铁电性和介电性方面有很大的优势,但却对铁磁性能有抑制作用。综合来看, SAG 方法对于多铁性陶瓷的制备来说优点多于缺点,其在以后多铁性陶瓷制备过程中值得借鉴。关键词: 多铁性材料、核壳结构、铁电性、介电性、铁磁性、溶胶凝胶法华中科技大学硕士学位论文 II Abstract Composite multiferroic which operate by coupling the ic and electric properties between two materials, shows oelectric effect by coupling of oconstriction and piezoelectr icity. In this materials,external electric field can lead to ization, vice versa, polarization can be induced by ic field. Because of the potential of application, the re search of multiferroic e one of the important area in condensed matter physics. The main contents of this paper are as the following: (1) CoFe 2 O 4 –BaTiO 3 multiferroic core-shell-type nanostructures were synthesized by a two-step wet chemical procedur bining co-precipitation and sol – gel techniques. The nature of bonding of oleic acid with CoFe 2 O 4 nanoparticles is determined by Fourier transform infrared spectroscopy ,and the ferrofl uid was Prepared by the dispersation of the surface-modified ferrite into the surface-modi fied ferrite,which can disperse into the Stearic Acid imedia easily. X-ray diffraction confirmed the presence of both the CoFe 2 O 4 of spinel and the BaTiO 3 of perovskite phas es, and no secondary phases were detected by