铁电材料的纳米尺度压电响应力显微术研究进展

压电响应力显微术是在原子力显微镜的基础上,利用材料自身逆压电效应来探测样 品表面形变的一类技术总称.现已作为铁电材料研究的重要手段,应用于纳米尺度畴结构的三 维成像、畴结构的动态研究、畴结构控制和微区压电、铁电、漏电等物理性能表征等领域.本 文就近年来利用压电响应力显微术对铁电材料的研究方面作一综述.     

基于弛豫铁电单晶的热释电焦平面研究

PMN-PT是一种综合性能优异的新型热释电材料.本文以PMN-PT单晶作为热释电探测器材料,开展了8×1线列探测器的芯片结构设计及器件关键工艺研究,获得了8元热释电探测器芯片,电压响应率约280N/W.同时,实现了8元热释电光敏芯片与8元读出电路的耦合互连,得到了8元热释电焦平面原型器件,并进行了性能测试.由于读出电路...     

PMN-PT驰豫铁电单晶及其超声换能器性能研究

测试了PMN－PT（67／33）切型铁电单晶的机电性能,分析了该晶体与常用压电材料在微观结构和机电性能上差异。对该压电单晶未调末调制下纵向长度伸缩振动模超声换能器性能进行了理论分析。讨论了压电单晶的机械和介电损耗对超声换能器性能的规律。     

弛豫铁电单晶及织构陶瓷的研究进展

综述了近年来弛豫铁电单晶和织构陶瓷的制备及其介电、压电性能的研究进展。弛豫铁电单晶的制备方法主要有高温溶液法、布里奇曼法和固态再结晶法，尺寸可达40mm以上，(001)切片压电常数d33最大可达3000pC／N，k3达到0.93，但是成分不均匀仍是影响晶体压电性能的一个主要因素。织构陶瓷的制备方法主要为固态再结晶法(TGG法和RTGG法)，其耗时短、成本低，压电性能可达到单晶的60％～80％，介电常数甚至可以超过部分单晶，是一个新的发展方向。     

锰掺杂对PMN-PT陶瓷介电和压电特性的影响

采用氧化物固相反应法制备了Mn掺杂0.67Pb（Mg1/3Nb2/3）O3-0.33PbTiO3陶瓷，研究了锰掺杂量对陶瓷相结构、介电和压电性能的影响。实验发现，随着锰掺杂量的增加，陶瓷焦绿石相含量的逐渐较少，材料变“硬”。即当锰掺杂量少于1.5mol％时，介电系数ε、压电常数d33和机械品质因数Qm逐渐增加，介电损耗tanδ减少。随着锰掺杂量的进一步增加，弛豫程度变得更加明显。当压电陶瓷组分中锰掺杂量为1.5mol％时，其介电和压电性能各为：ε=2300，kp=0.54，Qm=900，tanδ=0.004，d33=400pC/N，适于制作大功率压电陶瓷变压器。     

PMN-PT弛豫铁电固溶体的定向凝固组织与结晶习性

研究了(1-x)Pb(Mg1／3Nb2／3)O3-xPbTiO3(简称PMN—PT或PMNT)系铁电固溶体在坩埚下降法定向凝固过程中的结晶与晶粒生长习性．结果表明，随着坩埚下降速度的加快和PbTiO3含量的降低，陶瓷晶粒的择优生长方向由[111]逐渐向[110]转变．     

PMNT单晶电畴结构随组分与结构的变化

利用多种方法观察了弛豫型铁电单晶ＰＭＮＴ中电畴结构随组分与结构的演变过程与特征．观察发现,在ＰＭＮ－ＰＴ的三方相区内,随ＰＴ含量的增加,电畴结构表现出微畴一（亚微畴）－不规则宏畴一规则宏畴转变历程;在三方－四方相变中,非１８０°电畴发生７１°（或１０９°）宏畴－９０°宏畴的转化,同时电畴图像变得更为规则．根据不同组分ＰＭＮＴ电畴的显示特征,提出晶体的最大双折射率可以作为度量其弛豫性强弱的光学参数．观察到了电畴的分布不均匀与多级结构现象,前者与组分或结构的起伏有关,后者与多期式马氏体转变有关．本文还分析了偏光显微镜、ＤＩＣ、ＳＥＭ、ＳＥＡＭ等观察方法中电畴的成像特征．     

等静压力诱导的PMN-PT单晶介电弛豫特性研究

研究了不同等静压力下的PMN-PT单晶的介电常数(εr)与温度(T)的关系,以及常温下介电常数(εr)及损耗(tanδ)与压力(p)之间的关系.发现了PMN-PT单晶在压力作用下出现明显的介电频率弥散现象.当等静压力增大到一定压力时,PMN-PT单晶的介电常数值迅速降低,介电频率弥散更加显著,且出现弛豫特性,介电损耗的弛豫特征更加明显.随着频率的增加,介电损耗峰对应的峰值压力向高压方向移动.其根本原因是压力诱导的介电-压力弛豫特性导致的.     

PMN-PT弛豫铁电粉体的溶胶-凝胶法制备及其性质

以无机盐或氧化物Ｎｂ_２Ｏ_５、ＭｇＯ、ＴｉＣｌ_４和Ｐｂ（ＡＣ）_２、３Ｈ_２Ｏ为原材料,柠檬酸和ＥＤＴＡ为复合螫合剂,乙二醇为溶剂,分别制备Ｎｂ、Ｍｇ－Ｎｂ、Ｔｉ和Ｐｂ的有机化合物前驱液,采用溶胶－凝胶工艺制备ＰＭＮ－ＰＴ弛豫铁电陶瓷粉体及其烧结体．讨论了制备工艺和螯合剂等对金属有机化合物溶液的性质、材料物相形成和介电性能的影响．     

弛豫铁电单晶压差水听器有限元设计

分析了[001]切型PMNT弛豫铁电单晶各向异性的压电特性,利用有限元软件对PMNT弛豫铁电单晶压差水听器进行仿真计算,设计制作了压电三叠片压差水听器。仿真与测试结果表明:[001]切型PMNT弛豫铁电单晶可近似等效为横观各向同性材料,在轴对称结构压差水听器设计中具有一定的应用优势,压差水听器的测试结果与有限元仿真结果相符。     

Piezoresponse force microscopy studies of nanoscale domain structures in ferroelectric thin film

Piezoresponse force microscopy was used to perform studies of nanoscale domain imaging, limit of ferroelectric nano-sized grains and electric field-induced displacement behavior of domain structures in ferroelectric PZT thin film. Nanoscale 180° and 90° domain configurations as small as 30 nm in size were clearly visualized in the individual grains. It was demonstrated that domain configuration was strongly dependent on the size of the grains. The limit of ferroelectric nano-sized grains was found to be smaller than 25 nm. Nanoscale displacement versus field hysteresis loops were obtained in ferroelectric domains of PZT thin film, and discussed in terms of phenomenological theory.     

Piezoresponse force microscopy and recent advances in nanoscale studies of ferroelectrics

In this paper, we review recent advances in piezoresponse force microscopy (PFM) with respect to nanoscale ferroelectric research, summarize the basic principles of PFM, illustrate what information can be obtained from PFM experiments and delineate the limitations of PFM signal interpretation relevant to quantitative imaging of a broad range of piezoelectrically active materials. Particular attention is given to orientational PFM imaging and data interpretation as well as to electromechanics and kinetics of nanoscale ferroelectric switching in PFM.     

高性能PMN-PT系铁电单晶在医疗超声中的产业化进展

PMN-PT系铁电单晶因其出色的压电和高机电耦合系数的特性,在超声换能器领域具有非常好的应用前景。近年来,我国一些研究团队在铁电单晶的理论研究和晶体生长上取得了突破性成就,为铁电单晶在医疗超声领域的大规模应用奠定了坚实的基础。文章概述了近年来一些研究团队在铁电单晶上的研究进展,以及医用超声换能器领域中使用铁电单晶的工作进展,总结了国内超声企业在铁电单晶换能器产业化的进程。     

The growth striations and ferroelectric domain structures in Czochralski-grown LiNbO3 single crystals

The rotational striations and power striations are studied in LiNbO₃ crystals and one-to-one correspondence between the striations and temperature fluctuations is demonstrated. The ferroelectric domain structures related to the rotational striations and the power striations have been observed. The distribution of solute concentration in rotational striations is measured by means of energy dispersive X-ray analysis in the scanning electron microscope, and it has been concluded that the ferroelectric domain structures depend on the solute concentration gradient.     

Ferroelectric domain in PMN-xPT single crystal studied by piezoresponse force microscopy and finite-element analysis

Ferroelectric domain structures in (001)-cut Pb(Mg(1/3)Nb(2/3))O(3)-38%PbTiO(3) and (011)-cut Pb(Mg(1/3) Nb(2/3))O(3)-60%PbTiO(3) single crystals are studied by means of piezoresponse force microscopy (PFM). The out-of-plane- polarization (OPP) and in-plane-polarization (IPP) domain piezoresponse imaging reveals the domain and domain boundary configurations in these two different PbTiO(3)-content crystals. Finite-element analysis is carried out to illustrate the OPP and IPP-PFM imagings mechanism and interpret the domains superposition phenomenon during PFM imaging.     

Chemical force microscopy of single live cells

Traditionally, cell surface properties have been difficult to study at the subcellular level, especially on hydrated, live cells. Here, we demonstrate the ability of chemical force microscopy to map the hydrophobicity of single live cells with nanoscale resolution. After validating the technique on reference surfaces with known chemistry, we probe the local hydrophobic character of two medically important microorganisms, Aspergillus fumigatus and Mycobacterium bovis, in relation with function. Applicable to a wide variety of cells, the chemically sensitive imaging method presented here provides new opportunities for studying the nanoscale surface properties of live cells and for understanding their roles in mediating cellular events.     

Laser-induced dislocation structures in copper single crystals

Mechanical Stress fields of nearly radial symmetry are produced by focused laser irradiation on (111) surfaces of copper single crystals. The dislocation structures in the vicinity of the heat-affected zone can be revealed with the aid of an etch pit technique. The observed etch pit pattern is in very good agreement with calculations based on dislocation theory.     

Atomic force microscopy on tree-like crystals in polyvinylidene fluoride blends

Polyvinylidene fluoride (PVDF), in homogeneous blends with an amorphous polymer under specific conditions, forms crystals with a tree-like architecture. Tree-like crystals have a loose fractal structure of crystalline branches which are impregnated with the amorphous polymer. In a previous study, this spectacular morphology was investigated in blends of PVDF and a random copolymer of styrene and methylmethacrylate (SMMA, 13% wt/wt styrene) by light microscopy. The crystal growth was interpreted in terms of a rate competition of crystallization and interdiffusion. The submicroscopic structure of tree-like PVDF spherulites has now been characterized by atomic force microscopy. Surface profiles were prepared by etching PVDF/SMMA blend films with toluene. The tree-like spherulites proved to be less disordered than expected. Their core consists of a compact array of lamellae, the planes of which are periodically twisted, producing a ring pattern. Near the crystallizing front, branches grow, separated from each other, into the amorphous phase. They are internally as compact as the core, but are covered by a loose fur of disordered lamellae. The tree-like appearance of these crystals comes from frequent splitting of the branches into twigs. Crystallographic bifurcation as in dendritic crystals was not observed. At interfaces between two tree-like crystals, the lamellae form patterns of backfolding. © 1998 Chapman & Hall     

Fracture studies of tungsten single crystals

For fracture studies on oriented W monocrystalline specimens it is necessary to produce very sharp, stopped precracks, which presents difficulties in the case of W. The procedure and technique to produce precracks is described. The fracture experiments gave strong indications for a preference of the {100} planes as cleavage planes. The {110} planes successfully resist crack propagation, although they are the planes with the lowest surface energy. Crack propagation on both the {110} crack system and {100} crack system is strongly influenced by the crack front orientation. The appearance of the {121} plane as a cleavage plane in our experiments makes further studies with oriented W monocrystalline specimens desirable.