【作者】 赵静；

【导师】 路晓艳；

【作者基本信息】 哈尔滨工业大学 ， 建筑与土木工程（专业学位）， 2017， 硕士

【摘要】 铁电材料具有传感、驱动等多种功能,已经被广泛应用到电子机械、航天等领域。近年来弛豫铁电单晶因其良好的介电、电致伸缩和压电等性能受到国内外诸多研究者的关注。其中,钙钛矿固溶体铌锌酸铅-钛酸铅Pb(Mg1/3Mb2/3)O3-x Pb Ti O3(PMN-x PT)晶体是最典型的弛豫铁电晶体之一。PMN-x PT是由PMN和PT混合形成的复杂固溶体,随着PT组分x的变化,晶体内部会发生结构相变,造成性能上很大的差异。可见,晶体的宏观性能和微观畴结构是密切相关的。研究铁电晶体的畴结构能更好了解晶体的内在机理,揭示畴结构对宏观物性的影响,对提高材料的压电性能以及无铅压电材料的设计具有重要的意义和参考价值。本论文系统的研究了PMN-0.25PT、PMN-0.28PT、PMN-0.36PT三个组分(001)面铁电、介电、压电、畴结构的性能。通过实验测量介电和铁电极化性能在温度以及电场的变化情况,从实验上确定晶体的相变温度以及不同温度下的矫顽场。通过在晶体[001]C方向施加矫顽场附近大小的极化电场对晶体进行极化处理,观察极化后畴结构的变化,测试出相应的压电系数,进而获得不同极化条件下的压电系数的差异。将畴结构和压电性能进行关联,分析不同的畴形态和尺寸对压电性能的影响。随后改变晶体的温度,观察畴结构随温度的变化,着重关注在相变温度附近的现象,研究晶体在相变点时的行为以及相变前后的变化过程。此外,对于PMN-0.25PT晶体除了(001)面还研究了其他两个切面(011)面和(111)面的畴结构和性能,对比同一组分晶体沿着不同方向极化后畴结构和压电性能的差别。最后对于PMN-0.25PT沿着[100]C方向采用高温极化的技术,在极化过程中沿着[001]C方向观察畴结构对电场和温度响应,改变极化的温度和电场条件调控畴结构优化晶体的性能。本论文的研究给出了PMN-PT畴结构和宏观性能之间的关联,获得了畴尺寸与材料性能之间的关系,为进一步优化PMN-PT单晶性能提供了实验方法和依据。更多还原

【Abstract】 Ferroelectric materials have many functions,such as sensing,driving and so on,and have been widely used in electro-machanical,aerospace and other fields.Recently,PMN-PT has attracted the attention of many researchers because of its dielectric,electrostrictive,piezoelectric effects and other properties.Pb(Mg1/3Mb2/3)O3-x Pb Ti O3(PMN-x PT)crystals are one of the most typical relaxor ferroelectric crystals.PMN-x PT is a complex solid solution formed by the mixing of PMN and PT,and structural phase transition will occur in the crystal with the change of ratio x in PT,causing a big difference in performance.It is thus clear that the macro-properties of crystals are closely related to their microscopic domain structures.Obviously,the research on the domain structures of ferroelectric crystals makes it easier to understand the internal mechanism of crystal and the influence of domain structures on microscopic physical properties,it is of great significance and reference to improve the piezoelectric properties of materials and the design of lead-free Piezoelectric Materials.This paper has systematically studied the surface ferroelectric,dielectric,electromechanical,and domain structure properties of three components: PMN-0.25 PT,PMN-0.28 PT and PMN-0.36 PT.The phase transition temperature and the coercive field at different temperatures are determined by dielectric and ferroelectric experiments.The polarization of the electric field along the crystal [001]C direction is treated by using different polarization electric fields in the coercive field.Observe the change of domain structure after polarization by using polarizing microscope,test out the corresponding electromechanical coefficients and thus understand the difference of electromechanical coefficients under different polarization conditions.Analyze the effects of different domain shapes and sizes on the mechanical and electrical properties by connect the domain structure with mechanical and electrical properties.Then change the temperature of the crystal and observe the change of domain structure with temperature,especially the phenomenon near the phase transition temperature and the behavior of crystal at the phase transition point.In addition,for the PMN-0.25 PT crystal,besides the(001)plane,the domain structures and properties of the other two planes(011)and(111)have been studied,and the difference of domain structure and mechanical and electrical properties between the same component crystals in different directions is compared.In the end,for the PMN-0.25 PT crystal,use the high temperature polarization technique along the [100]C direction,and during the polarization process observe the response of domain structure to electric field and temperature along the [100]C direction.Change the polarization temperature and electric field condition,control domain structure,optimize crystal performance.The results of this paper advance the study of the relation between PMN-PT domain structure and macroscopic properties,and provid the experimental method and basis for optimizing the performance of PMN-PT single crystal.更多还原