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西南科技大学本科生毕业论文
Southwest university of science and technology
本科毕业论文
水热法制备Gd诱导PbWO4分等级结构的
形成过程及机理研究
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学院名称 专业名称 学生姓名 学 号 指导教师
材料科学与工程学院
材料物理 刘旭冬 20060302 熊鹰 博士
二〇一〇年六月
西南科技大学本科生毕业论文 Ⅰ
3+
水热法制备Gd诱导PbWO4分等级结构的
形成过程及机理研究
摘要：纳米材料的控制合成是实现材料性能调控及其应用的基础，研究其控制合成机理尤为重要。本文以Na2WO4、Pb(NO3)2和Gd(NO3)3为原料，在不同比例的乙二醇（EG）与H2O溶剂中，采用简单的液相直接沉淀法合成钨酸铅(PbWO4)微晶，研究稀土阳离子Gd3+在PbWO4晶体的成核阶段对其低维有序结构的可控合成的机理。用XRD、SEM对样品的物相、微观形貌进行表征。结果表明：合成出来的最终样品均为纯的四方相钨酸铅微晶，且随着Gd3+掺入量的增加，（112）面和（200）面等衍射峰均向高角度方向漂移，这说明了Gd3+可能进入了PbWO4晶格并取代了Pb2+的位置，同时不同Gd3+掺入量对应的产物的SEM形貌有明显的差异，该结果表明Gd3+在PbWO4纳米晶体成核阶段可以对其进行微观结构及形貌（显微结构）的控制。此外，随着乙二醇比率的增加晶体沿纵轴方向的生长受到阻碍，乙二醇可能是在成核初期选择性的吸附在晶体某些表面控制其生长，从而达到对形貌的控制。
关键词：纳米材料； PbWO4晶体； Gd3+离子； 可制合成； 形貌
西南科技大学本科生毕业论文
Water hot legal system for the grade structure pbwo4 Gd3+ induce the formation of the research process and
mechanisms
Abstract: Controlled-synthesis of nanostructure materials is the basis of the modification of their properties and application. Especially, it is very important to explore the mechanism of controlled-synthesis. In this thesis, Gd3+-doped PbWO4 microcrystals were prepared by a facile liquid-phase precipitating method in the mixed-solvent system of ethylene glycol (EG)/H2O with different volume ratio, using Na2WO4, Pb(NO3)2 and Gd(NO3)3 as raw materials, and the probable mechanism for the formation of Gd
3+
-doped PbWO4 low-dimensional ordered-structure in the nucleation process under
the inducement of Gd 3+ ions was roughly explored. X-ray diffraction (XRD) results revealed that all of Gd 3+-doped PbWO4 was pure tetragonal lead tungstate and the reflection peak of (112) shifted obviously toward higher angle with increasing the Gd 3+ doping concentration, indicating that the Gd 3+ ions were likely to enter PbWO4 crystal lattice to substitute Pb2+ sites. Moreover, scanning electron microscopy (SEM) images showed that the morphology of Gd 3+-doped PbWO4 microcrystals remarkably varied with the concentration of Gd
3+
. These
above-mentioned phenomena suggested that in the nucleation stage of PbWO4 nanocrystals, Gd 3+ ions could modify not only the microscopic structure (such as defects) but also the morphology. Furthermore, it was found that the ratio of EG/H2O in the mixed solvent had obviously influence to the morphology of Gd
3+
-doped PbWO4 microcrystals, which could be possibly explained that in the
nucleation stage of Y-doped PbWO4 nanocrystals, EG was selectively adsorbed on some certain crystallographic planes to control the growth direction.
Keywords：Nanomaterials， PbWO4 crystals， Gd3+ ions， Controlled-synthesis， Morphology
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西南科技大学本科生毕业论文
目 录
摘 要………………………………………………………………………………..Ⅰ Abstract…………………………………………………….…………………………Ⅱ 第1章 绪 论……………………………………………………………..……........... 6
前言……………………………………………………………..……………………7 1.1 PbWO4单晶研究进展 ......................................................................................... 18 1.1.1 PbWO4的晶体结构 .......................................................................................... 18 1.1.2 掺杂PbWO4晶体的研究现状 ......................................................................... 18 1.2 钨酸盐材料的表征手段和常用计算公式 .......................................................... 18 1.2.1 物相表征和形态分析 ................................................................................... 18 1.2.2 成分分析 ....................................................................................................... 18 1.2.3 性质分析 ....................................................................................................... 18 1.2.4 常用的计算公式 ........................................................................................... 18 1.3 溶剂(水)热法制备PbWO4及其它钨酸盐微晶的研究进展 .............................. 18 1.4 本论文的选题背景与主要研究内容 .................................................................. 18 第2章 实验过程 ............................................................................................................. 18
2.1 实验药品及仪器 .................................................................................................. 18 2.2 实验方法 .............................................................................................................. 18 2.3 实验流程 .............................................................................................................. 18 2.4 本实验4个体系的PbWO4样品的制备 ............................................................ 19 2.5 对样品的结构及表面形貌的表征 ...................................................................... 18 第3章 结果与讨论 ......................................................................................................... 18
3.1 不同Gd3+参杂浓度下所制样品的表征 ............................................................. 21
3.1.1 0%EG/H2O体系下不同Gd3+-PbWO4的表征 2.1.2 30%EG/H2O体系下不同Gd3+-PbWO4的表征 3.1.3 50%EG/H2O体系下不同Gd3+-PbWO4的表征 3.1.4 70%EG/H2O体系下不同Gd3+-PbWO4的表征 3.2 不同乙二醇浓度下所制样品的表征 .................................................................... 22
3.2.1 5%Gd3+：PbWO4时不同浓度乙二醇的表征 ........................................... 24 3.2.2 15%Gd3+：PbWO4时不同浓度乙二醇的表征 ......................................... 26
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