發(fā)布時間：2019-04-09 20:32

【摘要】：多鐵性磁電材料是集磁有序和電有序共存于一體的材料。CoFe2O4/BaTiO3復合塊體材料作為多鐵性磁電復合材料的代表體系,燒結(jié)致密過程中兩相之間的離子擴散和體系過高的漏電流是導致材料鐵電耦合系數(shù)較低的主要原因。因此,研究CoFe2O4/BaTiO3陶瓷體系在高溫燒結(jié)過程中兩相之間的離子擴散和反應(yīng)機理對于提高其磁電性能具有重要的意義。以溶膠凝膠法為基礎(chǔ),通過改變BaTiO3在CoFe204溶膠凝膠工藝路線中的加入方式,即CoFe2O4凝膠階段、CoFe2O4前驅(qū)體階段、CoFe2O4粉體合成后,制備了三種復合方式的CoFe2O4/BaTiO3陶瓷,分別標記為CoFe2O4(L)/BaTiO3陶瓷、CoFe2O4(P)/BaTiO3陶瓷、CoFe2O4(E)/BaTiO3陶瓷。研究了不同復合方式的CoFe2O4/BaTiO3陶瓷在燒結(jié)過程中結(jié)構(gòu)變化與性能之間的關(guān)系。稀土元素在SrFe12O19磁鉛礦結(jié)構(gòu)中有一定的固溶度,高含量的稀土摻雜會導致稀土鐵酸鹽的生成,出現(xiàn)原位共生的SrFe12O19/REFeO3磁電復合體系。采用微波輔助煅燒溶膠凝膠法制備Pr和Dy摻雜的Sr1-xRExFe12O19(x=0.15、0.25、0.5),研究了Pr和Dy在SrFe12O19結(jié)構(gòu)中的固溶度以及摻雜對結(jié)構(gòu)和磁性能的影響。探索了Pr和Dy摻雜的原位共生SrFe12O19 REFeO3/α-Fe2O3三元復合體系的生長機理、磁性能和微觀結(jié)構(gòu)之間的聯(lián)系,主要結(jié)論如下：1.燒結(jié)過程中的Co2+擴散與燒結(jié)溫度和復合方式密切相關(guān)。離子擴散難以程度決定了六方相BaTiO3的生成溫度。1200℃燒結(jié)溫度下,CoFe2O4(L)/BaTiO3陶瓷最容易發(fā)生離子擴散,CoFe2O4(E)/BaTiO3陶瓷界面離子擴散最難,容易生成第三相BaFe12019.2.1020℃下燒結(jié)的CoFe2O4(L)/BaTiO3陶瓷的電性能均低于其他兩種復合方式,一方面來自于較低的燒結(jié)溫度導致的低致密化。另一方面源于相對匹配的晶粒尺寸和良好的界面接觸導致的滲漏導電和界面極化。3. CoFc2O4(E)/BaTiO3陶瓷的電極化性能較為優(yōu)異,其中CoFe2O4的極限摩爾復合比例比例低于40%。CoFe204(E)/BaTi03(l:9)陶瓷的電極化性能最大,為5.24μC/cm2。4.Pr3+在磁鉛石礦的SrFe12O19結(jié)構(gòu)中固溶度在x=0.25左右,在摻雜比例為x=0.5時,得到了SrFe12019/PrFeO3/α-Fe2O3三相共存的結(jié)構(gòu),但三相的結(jié)構(gòu)和分布存在較大不同,使得相與相之間的耦合較差,磁性能較差。Dy3+在摻雜比例為x=0.5時,由于DyFeO3和SrFe12O19的同步析出,使得兩相顆粒分布均勻,且尺度較小,有助于SrFe12019/DyFeO3/α-Fe2O3三相之間的磁性耦合,其矯頑力高達6783.80e。
[Abstract]:Fe _ 2O _ 4 / BaTiO3 composite block material is the representative system of multi-ferroelectric composite material, which is composed of magnetic order and electric order. The ion diffusion between the two phases and the high leakage current in the sintering process are the main reasons for the low ferroelectric coupling coefficient of the materials. Therefore, the study of ion diffusion and reaction mechanism between the two phases in the sintering process of CoFe2O4/BaTiO3 ceramics at high temperature is of great significance for improving its magnetoelectric properties. Based on the sol-gel method, three kinds of composite CoFe2O4/BaTiO3 ceramics were prepared by changing the adding mode of BaTiO3 in the CoFe204 sol-gel process, I. E., CoFe2O4 gel stage, CoFe2O4 precursor stage and CoFe2O4 powder synthesis. CoFe2O4 (L) / BaTiO3 ceramics, CoFe2O4 (P) / BaTiO3 ceramics and CoFe2O4 (E) / BaTiO3 ceramics were labeled respectively. The relationship between structure change and properties of CoFe2O4/BaTiO3 ceramics with different composite modes during sintering was studied. The rare earth elements have a certain solid solubility in the structure of SrFe12O19 magnetite. High content of rare earth doping will lead to the formation of rare earth ferrate and in situ symbiosis of SrFe12O19/REFeO3 magnetoelectric composite system. The microwave-assisted calcined sol-gel method was used to prepare Pr and Dy doped Sr1-xRExFe12O19 (x = 0.15, 0.25, 0.5). The solid solubility of Pr and Dy in SrFe12O19 structure and the effect of doping on the structure and magnetic properties were studied. The growth mechanism, magnetic properties and microstructure of the in-situ symbiotic SrFe12O19 REFeO3/ 偽-Fe2O3 ternary composite system doped with Pr and Dy were investigated. The main conclusions are as follows: 1. The diffusion of Co2 in sintering process is closely related to sintering temperature and composite mode. The difficult degree of ion diffusion determines the formation temperature of hexagonal phase BaTiO3. When sintered at 1200 鈩，

本文編號：2455517