共焦显微拉曼光谱技术在铁电陶瓷材料中的应用研究

本文介绍了拉曼光谱技术的发展和共焦显微拉曼光谱技术特点,就厦门大学材料学院购置的美国普林斯顿仪器公司生产的TrIVISTA CrS557型三级共焦显微拉曼光谱仪使用的情况,简单概述共焦显微拉曼光谱技术在铁电陶瓷的应用研究,尤其是材料在外场作用下的原位拉曼观测方面的创新技术。国家自然科学青年基金(51302236); 福建省重大平台建设基金(2006L2003)资

铁电陶瓷的电畴及畴变观测研究进展

铁电陶瓷材料,特别是锆钛酸铅(PZT)在众多领域具有广泛的应用前景,影响其推广应用的主要因素是使用过程中外电、力场引起的材料性能的退化。观测铁电电畴及畴变的方法对研究其在外场下性能破坏机理、提高其使用的可靠性和预防其失效具有重要的理论和实际意义。本文比较了不同实验方法和测试技术的优缺点,对铁电陶瓷的电畴观测进行了综述,并简要总结了铁电陶瓷的畴变观测技术研究现状,指出了目前该领域研究中存在的问题

铁电陶瓷畴变的原位Raman谱观测

从Raman光散射原理出发,提出原位Raman谱观测畴变原理,探索建立铁电畴变的原位、无损和微区观测技术.通过对PLZT铁电陶瓷试样的90°原位旋转前、后Raman谱变化的观测,以及电场作用下PLZT铁电陶瓷试样畴变后Raman谱峰强变化的观测,证实可以利用Raman谱的变化来检测铁电陶瓷材料电畴的畴变

CO_2激光熔拉锥过程光功率控制研究

基于CO2熔拉锥技术,对熔拉锥设备的控制方法进行了改进。利用柱体Mie散射公式计算光纤在加工过程中的光能利用率,结合Grellier的热传导模型,确定了加工过程中激光功率增长与光纤拉伸距离之间的对应关系。利用计算结果,采用分段直线递增的方法对激光功率进行控制,简化了仪器控制的难度。实验得到锥腰直径2~3μm左右的熔锥光纤,锥腰和过渡区的形状和尺寸都得到了很好的控制

Phase Transitions in PLZT Ceramics Observed by In-situ Raman Spectroscopy

采用传统固相反应法制备了原子比zr/TI≈52/48,掺杂少量镧的锆钛酸铅(PlzT)铁电陶瓷材料,X射线衍射分析表明得到的陶瓷粉末样品为纯钙钛矿相。对PlzT铁电陶瓷材料进行不同温度下的原位rAMAn谱观测,得到了各rAMAn特征谱的频率和峰强随温度的变化规律。结果表明,从-200℃升温至600℃过程中,准同型相界附近的PlzT铁电陶瓷分别发生了两种相变:在0℃发生了单斜相到四方相的转变,而在350℃发生了四方相到立方相的转变;并且,在-150℃和250℃附近还可能分别发生低温单斜相到高温单斜相和混合相的相变。The PLZT ceramics(atomic ratio Zr/Ti≈52/48,doped with small amounts of La) were prepared by conventional solid state reaction technique and identified to be pure perovskite phase by XRD.To observe the phase transition in the PLZT ceramics,the in-situ Raman spectra were measured at different temperatures.Accordingly,the variations of characteristic Raman shifts and intensities of the modes with temperatures were obtained.It is confirmed that two types of phase transitions near morphotropic phase boundary(MPB) occurred at 0℃ from rhombohedral to tetragonal and at 350℃ from tetragonal to cubic,in the temperature range from-200℃ to 600℃.What's more,the phase transitions for rhombohedral from low.to high-temperature phases and mixed phases may take place near-150℃ and 250℃,respectively.国家自然科学基金(51302236); 福建省特种先进材料重点实验室基金(2006L2003)~

连续电解抛光工艺优化前后的钼丝性能比较

通过对比实验对钼丝的连续电解抛光液及工艺参数进行了优化,并研究连续电解抛光工艺优化前后钼丝的相关性能.结果表明,工艺优化后的钼丝表面形成了连续均匀的氧化膜,整体缺陷减少,表面平整度得到较大的改善,同时抗拉强度、显微硬度、耐蚀性、抗氧化性也有所提高,综合性能明显优于传统工艺得到的钼丝性能

IN SITU XRD INVESTIGATION OF DOMAIN SWITCHING IN FERROELECTRIC CERAMICS PLZT DURING AN ELECTRIC FATIGUE PROCESS

【中文摘要】利用SEM观察了未疲劳和疲劳铁电陶瓷极化试样的断口形貌.利用原位XRD观测了电疲劳过程中极化试样表面铁电电畴的变化,并记录了相应的剩余极化强度.实验结果表明:疲劳试样的主要断裂模式为沿晶断裂;随疲劳次数的增加,每次疲劳后试样表面I(002)减小,I(200)增加;每次疲劳后在外加电场作用下试样表面I(002)增加幅度和I(200)减小幅度随疲劳次数的增加而减少.这些现象说明:可翻转电畴的减少是剩余极化强度降低的主要原因;非协调高畴变应变形成大量沿晶微裂纹并导致疲劳试样主要断裂模式为沿晶断裂;沿晶微裂纹的形成和伸长主要发生在电疲劳的初期. 【Abstract】 An in situ XRD method was employed to identify variations of electric domains on the surfaces of poled PLZT samples during an electric fatigue process, and simultaneously, the related remnant polarization was measured. The SEM observation revealed that the major fracture mode for fatigued samples is intergranular. The diffraction intensities, I(002) and /I(200), after each cycle decreased and increased, respectively, and their magnitudes of the increment and decrement lowered as the number of cycles increased. It is suggested that the reduction in magnitude of remnant polarization is caused by the reduction in numbers of switch-able domains during a fatigue process. In addition, the incompatible high strain induced the intergranular micro-cracks in the material, which leads the major fracture mode for the fatigued sample to be intergranular. The formation and the elongation of micro-cracks in samples mainly occurred at earlier stage of electric fatigue

In-situ Raman Observation of Domain Switching near Crack Tip in PLZT Ferroelectric Ceramics

采用传统固相法制备了平均晶粒尺寸为5; mum的四方结构掺镧锆钛酸铅(PLZT)铁电陶瓷,在其表面涂银、切向预极化后刻蚀出刻槽,在刻槽表面压出维氏压痕并沿预极化方向施加外电场,利用Ra; man光谱原位观测了压痕裂纹尖端附近不同位置的畴变,分析了Raman软模E(2TO)和E(3TO+2LO)+B1峰的强度随观测点的变化规律。结果; 表明:在外电场作用下,裂纹尖端会发生电致应变和90°畴变;Raman谱和软模E(2TO)、E(3TO+2LO)+B1峰强度均会随着观测点距裂纹尖; 端距离的增大而减弱。Lanthanum-doped lead zirconate titanate (PLZT) ferroelectric ceramics; with average grain size of 5 mm and a tetragonal structure were prepared; by the conventional solid state reaction method, and then were surface; coated with silver and pre-polarized in tangential direction. Then a; groove was etched in the silvered surface of the ceramics, sbsequently; Vickers indentation was introduced on the groove surface and external; electric field was applied along the pre-polarization direction. The; domain switching at different positions near the indentation crack tips; were in-situ observed by Raman spectroscopy. The variation of the peak; intensity of Raman soft modes of E(2TO) and E(3TO+2LO)+B1 versus the; observation point was analyzed. The results show that the electric; induced strain and 90° domain switching occurred at crack tips under the; external electric field. The peak intensity of Raman spectrum and soft; modes of E(2TO) and E(3TO+2LO)+B1 decreased with the distance between; observation point and crack tip increasing.国家自然科学基金资助项目; 福建省自然科学基金资助项

In-situ Raman Observations for PLZT Ferroelectric Ceramics Under an Alternating Electric Field

采用传统固相法制备了掺镧锆钛酸铅（PLZT）铁电陶瓷，经不同方向极化后，进行了交变电场循环加载疲劳试验，原位测试了不同循环周次下的Raman谱和电滞回线，分析了Raman软模强度和剩余极化强度的变化规律。结果表明：此铁电陶瓷在交变电场作用下的畴变导致了Raman峰强度和铁电性能的下降；随循环周次的增加，Raman软模相对强度和相对剩余极化强度均先快速下降后再缓慢下降，且下降趋势由急变缓的拐点基本出现在循环106.2周次时；纵向极化试样的Raman谱软模相对强度和相对剩余极化强度随循环周次增加的下降幅度大于未极化和切向极化试样的。Lanthanum doped lead state reaction technique and polarized in zirconate titanate （PLZT） ceramics different directions. Then the cyclic were prepared by conventional solid loading fatigue experiment under an alternating electric field was conducted on the ceramics. The Raman spectra and hysteresis loops were in-situ measured at different cycles, and then the variations of Raman spectra intensity for soft modes and remanent polarization were analyzed. The results show that Raman spectra intensity and ferroelectricity of the ceramics decreased due to the domain switching produced during the fatigue process under the cyclic alternating electric field. With the increase of the cycles, the Raman relative intensity for soft modes and the relative intensity for remanent polarizationin decreased first rapidly then slowly with the same turning point at about 106.2 cycles. The Raman relative intensity for soft modes and the relative intensity for remanent polarizationin of the out-of-plane polarized specimen decreased with the largest reduction among those of non polarized and in-plane polarized specimens, with the cycle increasing.国家自然科学基金资助项目（51302236）;福建省自然科学基金资助项目（2014J01205

Combined Technology and Application of Trivista Laser Confocal Raman Spectrometer in Ferroelectric Ceramic Research

简述了拉曼光谱技术的优越性以及共焦显微拉曼光谱技术的特点,针对材料学科的科研测试需求,叙述了近年来三级共焦显微拉曼光谱仪与一系列机械平台装置联用后,在偏振场、力电场、温度场等外场作用下PLZT铁电陶瓷材料的拉曼原位观测实例,通过图谱分析讨论了PLZT铁电陶瓷材料在外场作用下的微观结构变化及其疲劳损伤机理。In this paper,the superiority of Raman spectroscopy and the characteristics of confocal micro Raman spectroscopy are briefly introduced.According to the demands of scientific research and test in the field of materials science,the in-situ observation application cases for PLZT ferroelectric ceramic materials under the external fields action of polarization field,force electric field and temperature field with the combined technology of mechanical devices for Trivista laser confocal micro Raman spectrometer in recent years are summarized,the micro structure′s changes and fatigue damage mechanisms of PLZT ferroelectric ceramic materials under external fields are analyzed and discussed by obtained Raman spectra.国家自然科学青年基金资助项目（51302236）; 福建省自然科学基金资助项目（2014J01205