bi4xndxti3o12的紫外光辐照化学合成工艺研究word格式论文.docxVIP

优秀毕业论文 精品参考文献资料 Classified Index: TB383 U.D.C: 666 Dissertation for the Master Degree in Engineering UV RADIATION CHEMICAL SYNTHESIS PROCESS OF Bi4-xNdxTi3O12 Candidate: Supervisor: Academic Degree Applied for: Speciality: Affiliation： Date of Defence: Degree-Conferring-Institution: Xiao Lihua Prof. Meng Qing-chang Master of Engineering Materials Science School of Mater. Sci. Eng. June, 2008 Harbin Institute of Technology 哈尔滨工业大学工学硕士学位论文 - I - 摘 要 本文采用溶胶-凝胶法(Sol-gel)通过紫外光辐照合成了钕掺杂钛酸铋BNT （Bi4-xNdxTi3O12, x=0, 0.25, 0.5, 0.75）粉体和薄膜。通过热重-差热分析(TG- DTA)、X射线衍射(XRD)、扫描电子显微镜(SEM)、原子力显微镜(AFM)等技 术手段对Sol-gel法制备的BNT粉体和薄膜进行了表征。 BNT溶胶胶体制备工艺优化过程表明，采用醋酸铋和硝酸钕及钛酸四丁酯 为原始组分，乙酸和乙二醇分别为催化剂和溶剂，可获得BNT透明溶胶。在凝 胶过程中，经紫外光辐照下制备的BNT（x=0.25）干凝胶粉体，在 350-400℃ 煅烧时主物相是Bi2O3和Bi2O3CO2，而在 450℃煅烧处理可获得单一钙钛矿相 BNT。紫外光辐照显著地的降低了BNT的晶化温度。研究表明，紫外光辐照促 进了凝胶在晶化过程中的化学反应： 2Bi2O3+3TiO2 Bi4Ti3O12；3Bi2Ti2O7+Bi2O3 2Bi4Ti3O12 通过溶胶-凝胶法在Pt(111)/Ti/SiO2/Si结构的基片上旋涂沉积BNT薄膜，经 紫外光辐照的薄膜于 300℃除去有机物，后经 500℃随炉热处理可得到均匀致 密的钙钛矿相BNT薄膜。薄膜平整致密，厚度约为 400nm。薄膜择优取向随着 Nd掺杂含量的增加趋向于c轴，其中以x=0.5，c轴择优取向最为明显。所得薄 膜具有较小的粗糙度，均在 2-4nm范围内。铁电性能测试结果表明，剩余极化 强度(Pr)和矫顽场(Ec)都随着Nd掺杂比例的增大而减小。 Bi4-xNdxTi3O12(x=0.25, 0.5, 0.75)薄膜的剩余 极化值 分别为 2.75μC/cm2 ， 11.59μC/cm2，10.24μC/cm2，其中钕掺杂量x=0.5 的薄膜表现出良好的铁电性 能。 关键词 Bi4-xNdxTi3O12薄膜；溶胶-凝胶；紫外光辐照；铁电性能 - II - Abstract With the help of ultraviolet irradiation, the ferroelectric BNT（Bi4-xNdxTi3O12, x=0, 0.25, 0.5, 0.75） powders and thin films were successfully synthesized by a sol-gel method. The crystallization process and structural characteristics of obtained BNT powders and thin films were analyzed by using TG-TDA, XRD, SEM and AFM methods. The transparent BNT solutions were prepared by using Bi(CH3COO)3 and Nd(NO3)3·5H2O, and Ti(C4H9O)4 as source materials, ethylene alcohol as a solvent and acetic acid (HOAc) as a catalyst. Under the condition of ultraviolet irradiation, the main constitutions of the BNT gel calcined at the range of 350°C to 400°C are Bi2O3 and Bi2O3CO2. The phase-pure BNT with layered pervoskite str