【作者】 王婧；

【导师】 赵明磊；

【作者基本信息】 山东大学 ， 凝聚态物理， 2013， 硕士

【摘要】 在课题组近期的研究工作中原创性地发现了一类特殊的与宏观界面形成相关的非铁电性压电多晶材料(Applied Physics Letters,95,022904,2009)。这类利用传统陶瓷工艺制备的包含Na0.5Bi0.5TiO3和Bi12TiO20的复相多晶陶瓷块体具有自然产生的宏观极性,因而不需施加电场极化就具有较强压电效应。与普通的铁电压电陶瓷和极性玻璃陶瓷相比,这类特殊压电陶瓷的宏观对称性更低,其宏观压电响应信号呈现三斜晶系的特征,且压电厚度切变振动模式较强。初步研究表明,这一特殊压电效应的起源与材料是否具有铁电性并无直接联系。本文主要对可能具有类似压电特性的Ba(Ti, Zr, Sn)O3基自然极性陶瓷进行了探索,对相关材料的压电性能、基本原料要求、微观及宏观机理进行了相关研究。一、首先进行了BaTiO3基自然极性陶瓷的探索。主要研究了以BaTiO3和Bi203粉料为原料、以固相反应法合成的陶瓷的反常压电效应,探索相关机理。在实验中先合成BaTiO3粉料,然后以不同的摩尔比和Bi2O3粉料混合。利用传统制备电子陶瓷材料的固相反应工艺制备了BaTiO3基自然极性压电陶瓷。实验结果表明,这种自然极性陶瓷不需要极化就具有压电效应,压电系数d33最高可到达11pC/N,并且在温度高于BaTiO3相变点仍具有压电性。X射线衍射(XRD)显示生成样品的物相主晶相是BaTiO3和Bi12TiO20。通过拉曼光谱(Raman spectra)和X射线光电子能谱分析(XPS)的研究,认为自然极性和非晶相中的BiO5多面体、Ti06八面体的畸变有关,这些畸变单元可能是自然极性形成的微观条件。认为Bi12TiO20对样品自然极性的形成起到非常重要的作用,而自然极性形成的宏观条件需要进一步研究。二、进行了BaTiO3-xBi12TiO20自然极性陶瓷的物性研究。在实验中先分别合成BaTiO3和Bi12TiO20粉料,然后以不同的摩尔比混合。通过研究发现在BaTiO3和Bi12TiO20较大的配比范围内制备的样品具有自然极性,并且表现出的压电常数d33基本上是先增大后减小。进一步选取BaTiO3-0.083Bi12TiO20自然极性陶瓷研究,发现其中Bi12TiO20相对应拉曼光谱的峰位相对于Bi12TiO20陶瓷的标准峰位均往低波数移动。Bi12TiO20相低波数段拉曼峰(P1-P14)与Bi05结构有关,能够说明具体的畸变出现在BiO5多面体中。通过拉曼光谱和XPS的研究推测自然极性和畸变的BiO5多面体和Ti06八面体有关。通过差式扫描量热(DSC)的分析,在样品烧结温度以上,Bi12TiO20处于融化的状态。这样不规则固液交界面上可能有一个宏观的应力梯度,应力梯度使微观的畸变单元取向,这或许是宏观极性产生的驱动力。三、分别探索了Ba(Zrx,Ti1-x)O3-yBi12TiO20系复相陶瓷和Ba(Snx,Ti1-x)O3-y Bi12TiO20系复相陶瓷中可能存在的自然极性。首先合成纯相的Ba(Zrx,Ti1-x)O3(x=0.25,x=0.50,x=1)粉料,通过介电温谱可以看到相变点都移到了室温以下,在室温附近为立方相。通过固相反应可以制备Ba(Zrx,Ti1-x)O3-yBi12TiO20系复相自然极性陶瓷。发现在Zr逐渐取代Ti的过程中,自然极性仍然存在,但压电活性逐渐减小,当x=1时,压电性消失。通过退火发现自然极性的产生和温度梯度有一定的关系。以同样方法先合成Ba(Snx,Ti1-x)O3(x=0.25, x=0.50, x=1),再和Bi12TiO20以一定的比例混合制备出Ba(Snx,Ti1-x)03-yBi12TiO20系复相陶瓷。研究发现在纯相的BaSnO3为基础的钙钛矿结构中也有这种自然极性现象。更多还原

【Abstract】 We have originally found a kind of special piezoelectric polycrystalline materials(Applied Physics Letters,95,022904,2009).The polycrystalline ceramics which made by ordinary sintering technique have piezoelectric effect without polarization.Compared with the ordinary ferroelectric piezoelectric materials,a lower symmetry of piezoelectric tensors was found in these NBT-BT ceramics,and the macroscopic symmetry is generally described as∞mm, equivalent to the hexagonal polar crystal class6mm. The research suggests that the special piezoelectricity has no direct relation with the ferroelectricity.We carried a series of research about this new type of piezoelectric material s,basic material requirements,the natural polarity microscopic and macroscopic mechanism.1.Explore the self-poled BaTiO3basic perovskite.The major research is the BaTiO3-xBi2O3ceramic natural polarity. The BaTiO3ceramic powder were synthetized firstly,and they were mixed with Bi2O3in different molar radio,the radio is1:x.Using the ordinary sintering way, we prepared the self-poled BaTiO3ceramic.The experiment results show that, this kind of natural polarity ceramics have normal and reverse piezoelectric effect without polarization,the normal piezoelectric effect parameter d33max. is.11PC/N,and the piezoelectricity will not disappear when the temperature higher than the phase transition point,When the samples(x=0.25) sintered at880℃,they have piezoelectricity, but at1100℃, the piezoelectricity disappears.The XRD shows that the self-poled samples main phases are BaTiO3and Bi12TiO20.By combining Raman spectroscopy and x-ray photoelectron spectroscopy techniques,we have identified the polarization has relation to the expanded BiO5an slightly distorted TiO6units in the BaTiO3-Bii2TiO20ceramic. 2. The self-poled ceramics which BaTiO3and Bi12TiO20mixed directly have been studied in this part. First of all, a large proportion of BaTiO3and Bi12TiO20can make self-poled ceramics, and the strength firstly increases and then reduced.We select the BaTiO3-0.083Bi12TiO20samples, as you can see, the Raman spectrum peaks, relative to Bi12TiO20ceramic standard peak, shift to lower wave numbers.This result is similar to the the conclusion of the first part,so we conclude that there are amorphous phases formation; the low wave number peaks (P1-P14) are related to the BiOs structure,it states that the specific distortions appears in this polyhedron. By Raman spectroscopy and XPS study,we speculate that the natural polarity may relate to the distorted BiOs polyhedron and the TiO6polyhedron.Through the DSC(Differential Scanning Calorimetry) analysis, the samples sintering temperature is at the Bi12TiO20melting state.This solid-liquid state offer a macroscopic force in the interface, the force maybe the cause of macpolarity.The macroscopic polarization maybe due to the partial alignment of these distorted units located within the grain boundary amorphous phases.3. Research the polarity of theBa(Zrx,Ti1-x)O3-yBi12TiO20and the Ba(Sn,Ti)O3-y Bi12TiO20self-poled ceramic.Firstly,we synthesized the pure phase different proportions of Ba(Zrx,Ti1-x)O3, through XRD, we see that it can synthesize the pure phase Ba (Zrx, Ti1-X) O3(x=0.25, x=0.50, x=1), and through the dielectric temperature spectrum we can see transformation temperature are moved to a room temperature, at room temperature, the structure is cubic phase. For piezoelectric properties, in Zr gradually replace Ti process,the natural polarity still exist, but the piezoelectric activity declines, when x=1, natural polarity disappears. And we found natural polarity has a certain relationship with temperature gradient by annealing, the solid liquid interface state make polarization produced. Then synthetized Ba (Snx, Ti1-x) O3(x=0.25, x=0.50, x=1), with certain proportion mixing Bi12TiO20and found this natural polarity phenomenon in the pure phase BaSnO3based perovskite structure, further expand the self-poled ceramic range.更多还原